diff --git a/DESCRIPTION b/DESCRIPTION
index 79205ce58e..cbe0a368e2 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -177,6 +177,8 @@ Collate:
     'grob-dotstack.R'
     'grob-null.R'
     'grouping.R'
+    'properties.R'
+    'margins.R'
     'theme-elements.R'
     'guide-.R'
     'guide-axis.R'
@@ -201,7 +203,6 @@ Collate:
     'layer-sf.R'
     'layout.R'
     'limits.R'
-    'margins.R'
     'performance.R'
     'plot-build.R'
     'plot-construction.R'
diff --git a/NAMESPACE b/NAMESPACE
index 3868c746f0..f2c0e9e5dd 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -1,19 +1,25 @@
 # Generated by roxygen2: do not edit by hand
 
+S3method("$","ggplot2::element")
 S3method("$","ggplot2::gg")
 S3method("$","ggplot2::theme")
 S3method("$",ggproto)
 S3method("$",ggproto_parent)
+S3method("$<-","ggplot2::element")
 S3method("$<-","ggplot2::gg")
 S3method("$<-","ggplot2::mapping")
+S3method("[","ggplot2::element")
 S3method("[","ggplot2::gg")
 S3method("[","ggplot2::mapping")
 S3method("[",mapped_discrete)
+S3method("[<-","ggplot2::element")
 S3method("[<-","ggplot2::gg")
 S3method("[<-","ggplot2::mapping")
 S3method("[<-",mapped_discrete)
+S3method("[[","ggplot2::element")
 S3method("[[","ggplot2::gg")
 S3method("[[",ggproto)
+S3method("[[<-","ggplot2::element")
 S3method("[[<-","ggplot2::gg")
 S3method("[[<-","ggplot2::mapping")
 S3method(.DollarNames,ggproto)
@@ -23,12 +29,6 @@ S3method(autolayer,default)
 S3method(autoplot,default)
 S3method(c,mapped_discrete)
 S3method(drawDetails,zeroGrob)
-S3method(element_grob,element_blank)
-S3method(element_grob,element_line)
-S3method(element_grob,element_point)
-S3method(element_grob,element_polygon)
-S3method(element_grob,element_rect)
-S3method(element_grob,element_text)
 S3method(format,ggproto)
 S3method(format,ggproto_method)
 S3method(fortify,"NULL")
@@ -75,10 +75,6 @@ S3method(limits,character)
 S3method(limits,factor)
 S3method(limits,numeric)
 S3method(makeContext,dotstackGrob)
-S3method(merge_element,default)
-S3method(merge_element,element)
-S3method(merge_element,element_blank)
-S3method(merge_element,margin)
 S3method(pattern_alpha,GridPattern)
 S3method(pattern_alpha,GridTilingPattern)
 S3method(pattern_alpha,default)
@@ -330,6 +326,7 @@ export(draw_key_vline)
 export(draw_key_vpath)
 export(dup_axis)
 export(el_def)
+export(element)
 export(element_blank)
 export(element_geom)
 export(element_grob)
diff --git a/R/coord-sf.R b/R/coord-sf.R
index d603d57de7..63e5ed4a26 100644
--- a/R/coord-sf.R
+++ b/R/coord-sf.R
@@ -334,13 +334,13 @@ CoordSf <- ggproto("CoordSf", CoordCartesian,
 
     # we don't draw the graticules if the major panel grid is
     # turned off
-    if (inherits(el, "element_blank")) {
+    if (is_theme_element(el, "blank")) {
       grobs <- list(element_render(theme, "panel.background"))
     } else {
       line_gp <- gg_par(
-        col = el$colour,
-        lwd = el$linewidth,
-        lty = el$linetype
+        col = el@colour,
+        lwd = el@linewidth,
+        lty = el@linetype
       )
       grobs <- c(
         list(element_render(theme, "panel.background")),
diff --git a/R/geom-.R b/R/geom-.R
index e2d8806b35..94a829f4a8 100644
--- a/R/geom-.R
+++ b/R/geom-.R
@@ -245,7 +245,7 @@ eval_from_theme <- function(aesthetics, theme, class = NULL) {
     return(aesthetics)
   }
 
-  element <- calc_element("geom", theme) %||% .default_geom_element
+  el <- calc_element("geom", theme) %||% .default_geom_element
   class <- setdiff(class, c("Geom", "ggproto", "gg"))
 
   if (length(class) > 0) {
@@ -260,12 +260,12 @@ eval_from_theme <- function(aesthetics, theme, class = NULL) {
     # Inherit up to parent geom class
     if (length(class) > 0) {
       for (cls in rev(class)) {
-        element <- combine_elements(theme[[cls]], element)
+        el <- combine_elements(theme[[cls]], el)
       }
     }
   }
 
-  lapply(aesthetics[themed], eval_tidy, data = element)
+  lapply(aesthetics[themed], eval_tidy, data = S7::props(el))
 }
 
 #' Graphical units
diff --git a/R/geom-label.R b/R/geom-label.R
index a9d288996f..652ae9b39b 100644
--- a/R/geom-label.R
+++ b/R/geom-label.R
@@ -88,7 +88,7 @@ GeomLabel <- ggproto("GeomLabel", Geom,
     data <- coord$transform(data, panel_params)
     data$vjust <- compute_just(data$vjust, data$y, data$x, data$angle)
     data$hjust <- compute_just(data$hjust, data$x, data$y, data$angle)
-    if (!is_margin("margin")) {
+    if (!is_margin(label.padding)) {
       label.padding <- rep(label.padding, length.out = 4)
     }
 
diff --git a/R/guide-.R b/R/guide-.R
index 8d26a95628..a888659cf1 100644
--- a/R/guide-.R
+++ b/R/guide-.R
@@ -376,6 +376,7 @@ Guide <- ggproto(
   # Renders tickmarks
   build_ticks = function(key, elements, params, position = params$position,
                          length = elements$ticks_length) {
+    force(length)
     if (!is_theme_element(elements)) {
       elements <- elements$ticks
     }
diff --git a/R/guide-axis-logticks.R b/R/guide-axis-logticks.R
index 37273cba06..9da147870d 100644
--- a/R/guide-axis-logticks.R
+++ b/R/guide-axis-logticks.R
@@ -119,7 +119,7 @@ guide_axis_logticks <- function(
     allow_null = TRUE
   )
   check_bool(expanded)
-  check_inherits(short.theme, c("element_blank", "element_line"))
+  check_inherits(short.theme, c("ggplot2::element_blank", "ggplot2::element_line"))
 
   new_guide(
     available_aes  = c("x", "y"),
diff --git a/R/guide-axis-theta.R b/R/guide-axis-theta.R
index 5183e802fc..b75528d347 100644
--- a/R/guide-axis-theta.R
+++ b/R/guide-axis-theta.R
@@ -154,7 +154,7 @@ GuideAxisTheta <- ggproto(
     }
 
     offset <- max(unit(0, "pt"), elements$major_length, elements$minor_length)
-    elements$offset <- offset + max(elements$text$margin %||% unit(0, "pt"))
+    elements$offset <- offset + max(elements$text@margin %||% unit(0, "pt"))
     elements
   },
 
@@ -184,7 +184,7 @@ GuideAxisTheta <- ggproto(
 
   build_labels = function(key, elements, params) {
 
-    if (inherits(elements$text, "element_blank")) {
+    if (is_theme_element(elements$text, "blank")) {
       return(zeroGrob())
     }
 
@@ -198,7 +198,7 @@ GuideAxisTheta <- ggproto(
 
     # Resolve text angle
     if (is.waiver(params$angle) || is.null(params$angle)) {
-      angle <- elements$text$angle
+      angle <- elements$text@angle
     } else {
       angle <- flip_text_angle(params$angle - rad2deg(key$theta))
     }
@@ -268,20 +268,20 @@ GuideAxisTheta <- ggproto(
     key <- params$key
     key <- vec_slice(key, !is.na(key$.label) & nzchar(key$.label))
     labels <- validate_labels(key$.label)
-    if (length(labels) == 0 || inherits(elements$text, "element_blank")) {
+    if (length(labels) == 0 || is_theme_element(elements$text, "blank")) {
       return(list(offset = offset))
     }
 
     # Resolve text angle
     if (is.waiver(params$angle %||% waiver())) {
-      angle <- elements$text$angle
+      angle <- elements$text@angle
     } else {
       angle <- flip_text_angle(params$angle - rad2deg(key$theta))
     }
     angle <- key$theta + deg2rad(angle)
 
     # Set margin
-    margin <- rep(max(elements$text$margin), length.out = 4)
+    margin <- rep(max(elements$text@margin), length.out = 4)
 
     # Measure size of each individual label
     single_labels <- lapply(labels, function(lab) {
@@ -365,7 +365,7 @@ GuideAxisTheta <- ggproto(
 
 theta_tickmarks <- function(key, element, length, offset = NULL) {
   n_breaks <- nrow(key)
-  if (n_breaks < 1 || inherits(element, "element_blank")) {
+  if (n_breaks < 1 || is_theme_element(element, "blank")) {
     return(zeroGrob())
   }
 
diff --git a/R/guide-axis.R b/R/guide-axis.R
index d445900071..03dffcaebd 100644
--- a/R/guide-axis.R
+++ b/R/guide-axis.R
@@ -259,10 +259,10 @@ GuideAxis <- ggproto(
   override_elements = function(params, elements, theme) {
     elements$text <-
       label_angle_heuristic(elements$text, params$position, params$angle)
-    if (inherits(elements$ticks, "element_blank")) {
+    if (is_theme_element(elements$ticks, "blank")) {
       elements$major_length <- unit(0, "cm")
     }
-    if (inherits(elements$minor, "element_blank") || isFALSE(params$minor.ticks)) {
+    if (is_theme_element(elements$minor, "blank") || isFALSE(params$minor.ticks)) {
       elements$minor_length <- unit(0, "cm")
     }
     return(elements)
@@ -379,7 +379,7 @@ GuideAxis <- ggproto(
     # Ticks
     major_cm <- convertUnit(elements$major_length, "cm", valueOnly = TRUE)
     range <- range(0, major_cm)
-    if (params$minor.ticks && !inherits(elements$minor, "element_blank")) {
+    if (params$minor.ticks && !is_theme_element(elements$minor, "blank")) {
       minor_cm <- convertUnit(elements$minor_length, "cm", valueOnly = TRUE)
       range <- range(range, minor_cm)
     }
@@ -450,13 +450,13 @@ GuideAxis <- ggproto(
     # rather than dimensions of this axis alone.
     if (has_labels && params$position %in% c("left", "right")) {
       where <- layout$l[-c(1, length(layout$l))]
-      just <- with(elements$text, rotate_just(angle, hjust, vjust))$hjust %||% 0.5
+      just <- with(S7::props(elements$text), rotate_just(angle, hjust, vjust))$hjust %||% 0.5
       gt <- gtable_add_cols(gt, unit(just, "null"), pos = min(where) - 1)
       gt <- gtable_add_cols(gt, unit(1 - just, "null"), pos = max(where) + 1)
     }
     if (has_labels && params$position %in% c("top", "bottom")) {
       where <- layout$t[-c(1, length(layout$t))]
-      just <- with(elements$text, rotate_just(angle, hjust, vjust))$vjust %||% 0.5
+      just <- with(S7::props(elements$text), rotate_just(angle, hjust, vjust))$vjust %||% 0.5
       gt <- gtable_add_rows(gt, unit(1 - just, "null"), pos = min(where) - 1)
       gt <- gtable_add_rows(gt, unit(just, "null"), pos = max(where) + 1)
     }
@@ -590,7 +590,7 @@ axis_label_priority_between <- function(x, y) {
 #'   overridden from the user- or theme-supplied element.
 #' @noRd
 label_angle_heuristic <- function(element, position, angle) {
-  if (!inherits(element, "element_text")
+  if (!is_theme_element(element, "text")
       || is.null(position)
       || is.null(angle %|W|% NULL)) {
     return(element)
@@ -612,8 +612,8 @@ label_angle_heuristic <- function(element, position, angle) {
   hjust <- switch(position, left = cosine, right = 1 - cosine, top = 1 - sine, sine)
   vjust <- switch(position, left = 1 - sine, right = sine, top = 1 - cosine, cosine)
 
-  element$angle <- angle %||% element$angle
-  element$hjust <- hjust %||% element$hjust
-  element$vjust <- vjust %||% element$vjust
+  element@angle <- angle %||% element@angle
+  element@hjust <- hjust %||% element@hjust
+  element@vjust <- vjust %||% element@vjust
   element
 }
diff --git a/R/guide-custom.R b/R/guide-custom.R
index f602bfc843..1a6d977c7f 100644
--- a/R/guide-custom.R
+++ b/R/guide-custom.R
@@ -113,7 +113,7 @@ GuideCustom <- ggproto(
 
     gt <- self$add_title(
       gt, title, title_position,
-      with(elems$title, rotate_just(angle, hjust, vjust))
+      with(S7::props(elems$title), rotate_just(angle, hjust, vjust))
     )
 
     # Add padding and background
diff --git a/R/guide-legend.R b/R/guide-legend.R
index b728752518..294c573725 100644
--- a/R/guide-legend.R
+++ b/R/guide-legend.R
@@ -325,7 +325,7 @@ GuideLegend <- ggproto(
     # Resolve title. The trick here is to override the main text element, so
     # that any settings declared in `legend.title` will be honoured but we have
     # custom defaults for the guide.
-    margin <- calc_element("text", theme)$margin
+    margin <- calc_element("text", theme)@margin
     title <- theme(text = element_text(
       hjust = 0, vjust = 0.5,
       margin = position_margin(title_position, margin, gap)
@@ -573,7 +573,7 @@ GuideLegend <- ggproto(
 
     gt <- self$add_title(
       gt, grobs$title, elements$title_position,
-      with(elements$title, rotate_just(angle, hjust, vjust))
+      with(S7::props(elements$title), rotate_just(angle, hjust, vjust))
     )
 
     gt <- gtable_add_padding(gt, unit(elements$padding, "cm"))
@@ -690,13 +690,17 @@ keep_key_data <- function(key, data, aes, show) {
 
 position_margin <- function(position, margin = NULL, gap = unit(0, "pt")) {
   margin <- margin %||% margin()
-  switch(
+  margin <- switch(
     position,
     top    = replace(margin, 3, margin[3] + gap),
     bottom = replace(margin, 1, margin[1] + gap),
     left   = replace(margin, 2, margin[2] + gap),
     right  = replace(margin, 4, margin[4] + gap)
   )
+  # We have to manually reconstitute the class because the 'simpleUnit' class
+  # might be dropped by the replacement operation.
+  class(margin) <- c("ggplot2::margin", class(margin), "S7_object")
+  margin
 }
 
 # Function implementing backward compatibility with the old way of specifying
diff --git a/R/margins.R b/R/margins.R
index 561aefb7bd..a010a87738 100644
--- a/R/margins.R
+++ b/R/margins.R
@@ -1,17 +1,21 @@
+#' @include properties.R
+
 #' @param t,r,b,l Dimensions of each margin. (To remember order, think trouble).
 #' @param unit Default units of dimensions. Defaults to "pt" so it
 #'   can be most easily scaled with the text.
 #' @rdname element
 #' @export
-margin <- function(t = 0, r = 0, b = 0, l = 0, unit = "pt") {
-  u <- unit(c(t, r, b, l), unit)
-  class(u) <- c("margin", class(u))
-  u
-}
+margin <- S7::new_class(
+  "margin", parent = S7::new_S3_class(c("simpleUnit", "unit", "unit_v2")),
+  constructor = function(t = 0, r = 0, b = 0, l = 0, unit = "pt") {
+    u <- unit(c(t, r, b, l), unit)
+    S7::new_object(u)
+  }
+)
 
 #' @export
 #' @rdname is_tests
-is_margin <- function(x) inherits(x, "margin")
+is_margin <- function(x) S7::S7_inherits(x, margin)
 is.margin <- function(x) lifecycle::deprecate_stop("3.5.2", "is.margin()", "is_margin()")
 
 #' @rdname element
diff --git a/R/plot-build.R b/R/plot-build.R
index 89e00abbd3..a8fd5498cc 100644
--- a/R/plot-build.R
+++ b/R/plot-build.R
@@ -337,7 +337,7 @@ table_add_tag <- function(table, label, theme) {
     return(table)
   }
   element <- calc_element("plot.tag", theme)
-  if (inherits(element, "element_blank")) {
+  if (is_theme_element(element, "blank")) {
     return(table)
   }
 
@@ -382,20 +382,20 @@ table_add_tag <- function(table, label, theme) {
   if (location %in% c("plot", "panel")) {
     if (!is.numeric(position)) {
       if (right || left) {
-        x <- (1 - element$hjust) * width
+        x <- (1 - element@hjust) * width
         if (right) {
           x <- unit(1, "npc") - x
         }
       } else {
-        x <- unit(element$hjust, "npc")
+        x <- unit(element@hjust, "npc")
       }
       if (top || bottom) {
-        y <- (1 - element$vjust) * height
+        y <- (1 - element@vjust) * height
         if (top) {
           y <- unit(1, "npc") - y
         }
       } else {
-        y <- unit(element$vjust, "npc")
+        y <- unit(element@vjust, "npc")
       }
     } else {
       x <- unit(position[1], "npc")
diff --git a/R/plot-construction.R b/R/plot-construction.R
index 21c2838b4d..5d9b550812 100644
--- a/R/plot-construction.R
+++ b/R/plot-construction.R
@@ -96,7 +96,7 @@ add_ggplot <- function(p, object, objectname) {
 #' Add custom objects to ggplot
 #'
 #' This generic allows you to add your own methods for adding custom objects to
-#' a ggplot with [+.gg].
+#' a ggplot with [+.gg][add_gg].
 #'
 #' @param object An object to add to the plot
 #' @param plot The ggplot object to add `object` to
@@ -115,7 +115,9 @@ add_ggplot <- function(p, object, objectname) {
 #' @keywords internal
 #' @export
 #' @examples
-#' S7::method(ggplot_add, list(S7::new_S3_class("element_text"), class_ggplot)) <-
+#' # making a new method for the generic
+#' # in this example, we enable adding text elements
+#' S7::method(ggplot_add, list(element_text, class_ggplot)) <-
 #'   function(object, plot, ...) {
 #'     plot + theme(text = object)
 #'   }
@@ -126,7 +128,6 @@ add_ggplot <- function(p, object, objectname) {
 #'   element_text(colour = "red")
 #'
 #' # clean-up
-#' rm("element_text", envir = ggplot_add@methods)
 ggplot_add <- S7::new_generic("ggplot_add", c("object", "plot"))
 
 S7::method(ggplot_add, list(S7::class_any, class_ggplot)) <-
diff --git a/R/properties.R b/R/properties.R
new file mode 100644
index 0000000000..493d787f05
--- /dev/null
+++ b/R/properties.R
@@ -0,0 +1,45 @@
+property_boolean <- function(allow_null = FALSE, default = TRUE) {
+  class <- S7::class_logical
+  class <- if (allow_null) S7::new_union(class, NULL) else class
+  validator <- function(value) {
+    if ((allow_null && is.null(value)) || is_bool(value)) {
+      return(character())
+    }
+    "must be a boolean"
+  }
+  S7::new_property(
+    class = class,
+    validator = validator,
+    default = default
+  )
+}
+
+property_choice <- function(options, allow_null = FALSE, default = NULL) {
+  force(options)
+  class <- S7::class_character
+  class <- if (allow_null) S7::new_union(class, NULL) else class
+  validator <- function(value) {
+    if (allow_null && is.null(value)) {
+      return(character())
+    }
+    if (!is_string(value)) {
+      return(as_cli("must be a string, not {.obj_type_friendly {value}}"))
+    }
+    if (value %in% options) {
+      return(character())
+    }
+    as_cli("must be one of {.or {.val {options}}}")
+  }
+  S7::new_property(
+    class = class,
+    validator = validator,
+    default = default
+  )
+}
+
+property_nullable <- function(class = S7::class_any, ...) {
+  S7::new_property(
+    class = S7::new_union(NULL, class),
+    ...
+  )
+}
diff --git a/R/save.R b/R/save.R
index e8febcbb0c..b4b1cc7226 100644
--- a/R/save.R
+++ b/R/save.R
@@ -244,7 +244,8 @@ get_plot_background <- function(plot, bg = NULL, default = "transparent") {
   if (!is_ggplot(plot)) {
     return(default)
   }
-  calc_element("plot.background", plot_theme(plot))$fill %||% default
+  bg <- calc_element("plot.background", plot_theme(plot))
+  try_prop(bg, "fill") %||% "transparent"
 }
 
 validate_device <- function(device, filename = NULL, dpi = 300, call = caller_env()) {
diff --git a/R/theme-current.R b/R/theme-current.R
index c6848c7d76..e42f8c1e68 100644
--- a/R/theme-current.R
+++ b/R/theme-current.R
@@ -40,7 +40,7 @@ NULL
 #' @return `set_theme()`, `update_theme()`, and `replace_theme()`
 #'   invisibly return the previous theme so you can easily save it, then
 #'   later restore it.
-#' @seealso [+.gg()]
+#' @seealso [add_gg()]
 #' @export
 #' @examples
 #' p <- ggplot(mtcars, aes(mpg, wt)) +
diff --git a/R/theme-defaults.R b/R/theme-defaults.R
index 7b5bb286f7..3823bf45c3 100644
--- a/R/theme-defaults.R
+++ b/R/theme-defaults.R
@@ -127,11 +127,12 @@ theme_grey <- function(base_size = 11, base_family = "",
     # by others
     line =               element_line(
                            colour = ink, linewidth = base_line_size,
-                           linetype = 1, lineend = "butt"
+                           linetype = 1, lineend = "butt", linejoin = "round"
                          ),
     rect =               element_rect(
                            fill = paper, colour = ink,
-                           linewidth = base_rect_size, linetype = 1
+                           linewidth = base_rect_size, linetype = 1,
+                           linejoin = "round"
                          ),
     text =               element_text(
                             family = base_family, face = "plain",
@@ -153,7 +154,7 @@ theme_grey <- function(base_size = 11, base_family = "",
 
     polygon =            element_polygon(
                            fill = paper, colour = ink,
-                           linewidth = base_rect_size, linetype = 1
+                           linewidth = base_rect_size, linetype = 1, linejoin = "round"
                          ),
 
     geom =               element_geom(
@@ -525,7 +526,7 @@ theme_void <- function(base_size = 11, base_family = "",
     line =               element_blank(),
     rect =               element_rect(
                            fill = paper, colour = NA, linewidth = 0, linetype = 1,
-                           inherit.blank = FALSE
+                           inherit.blank = FALSE, linejoin = "round"
                          ),
     polygon =            element_blank(),
     point =              element_blank(),
@@ -614,11 +615,11 @@ theme_test <- function(base_size = 11, base_family = "",
   t <- theme(
     line =               element_line(
                            colour = ink, linewidth = base_line_size,
-                           linetype = 1, lineend = "butt"
+                           linetype = 1, lineend = "butt", linejoin = "round"
                          ),
     rect =               element_rect(
                            fill = paper, colour = ink,
-                           linewidth = base_rect_size, linetype = 1
+                           linewidth = base_rect_size, linetype = 1, linejoin = "round"
                          ),
     text =               element_text(
                             family = base_family, face = "plain",
@@ -633,7 +634,7 @@ theme_test <- function(base_size = 11, base_family = "",
                          ),
     polygon =            element_polygon(
                            fill = paper, colour = ink,
-                           linewidth = base_rect_size, linetype = 1
+                           linewidth = base_rect_size, linetype = 1, linejoin = "round"
                          ),
     title =              element_text(family = header_family),
     spacing = unit(half_line, "pt"),
diff --git a/R/theme-elements.R b/R/theme-elements.R
index a16302b6db..0698bb12dd 100644
--- a/R/theme-elements.R
+++ b/R/theme-elements.R
@@ -81,55 +81,93 @@ NULL
 
 #' @export
 #' @rdname element
-element_blank <- function() {
-  structure(
-    list(),
-    class = c("element_blank", "element")
-  )
-}
+element <- S7::new_class("element", abstract = TRUE)
 
 #' @export
 #' @rdname element
-element_rect <- function(fill = NULL, colour = NULL, linewidth = NULL,
-  linetype = NULL, color = NULL, inherit.blank = FALSE, size = deprecated()) {
+element_blank <- S7::new_class("element_blank", parent = element)
+
+# All properties are listed here so they can easily be recycled in the different
+# element classes
+#' @include properties.R
+#' @include margins.R
+element_props <- list(
+  fill       = property_nullable(S7::class_character | S7::new_S3_class("GridPattern") | S7::class_logical),
+  colour     = property_nullable(S7::class_character | S7::class_logical),
+  family     = property_nullable(S7::class_character),
+  hjust      = property_nullable(S7::class_numeric),
+  vjust      = property_nullable(S7::class_numeric),
+  angle      = property_nullable(S7::class_numeric),
+  size       = property_nullable(S7::class_numeric),
+  lineheight = property_nullable(S7::class_numeric),
+  margin     = property_nullable(margin),
+  face       = property_choice(c("plain", "bold", "italic", "oblique", "bold.italic"), allow_null = TRUE),
+  linewidth  = property_nullable(S7::class_numeric),
+  linetype   = property_nullable(S7::class_numeric | S7::class_character),
+  lineend    = property_choice(c("round", "butt", "square"), allow_null = TRUE),
+  linejoin   = property_choice(c("round", "mitre", "bevel"), allow_null = TRUE),
+  shape      = property_nullable(S7::class_numeric | S7::class_character),
+  arrow      = property_nullable(S7::new_S3_class("arrow") | S7::class_logical),
+  arrow.fill = property_nullable(S7::class_character | S7::class_logical),
+  debug      = property_boolean(allow_null = TRUE, default = NULL),
+  inherit.blank = property_boolean(default = FALSE)
+)
 
-  if (lifecycle::is_present(size)) {
-    deprecate_warn0("3.4.0", "element_rect(size)", "element_rect(linewidth)")
-    linewidth <- size
+#' @export
+#' @rdname element
+element_rect <- S7::new_class(
+  "element_rect", parent = element,
+  properties = element_props[c("fill", "colour",
+                               "linewidth", "linetype", "linejoin",
+                               "inherit.blank")],
+  constructor = function(fill = NULL, colour = NULL, linewidth = NULL,
+                         linetype = NULL, color = NULL, linejoin = NULL,
+                         inherit.blank = FALSE, size = deprecated()){
+    if (lifecycle::is_present(size)) {
+      deprecate_warn0("3.4.0", "element_rect(size)", "element_rect(linewidth)")
+      linewidth <- size
+    }
+    S7::new_object(
+      S7::S7_object(),
+      fill = fill, colour = color %||% colour,
+      linewidth = linewidth, linetype = linetype, linejoin = linejoin,
+      inherit.blank = inherit.blank
+    )
   }
-
-  if (!is.null(color))  colour <- color
-  structure(
-    list(fill = fill, colour = colour, linewidth = linewidth, linetype = linetype,
-         inherit.blank = inherit.blank),
-    class = c("element_rect", "element")
-  )
-}
+)
 
 #' @export
 #' @rdname element
-#' @param lineend Line end Line end style (round, butt, square)
+#' @param linejoin Line join style, one of `"round"`, `"mitre"` or `"bevel"`.
+#' @param lineend Line end style, one of `"round"`, `"butt"` or `"square"`.
 #' @param arrow Arrow specification, as created by [grid::arrow()]
-element_line <- function(colour = NULL, linewidth = NULL, linetype = NULL,
-  lineend = NULL, color = NULL, arrow = NULL, arrow.fill = NULL,
-  inherit.blank = FALSE, size = deprecated()) {
-
-  if (lifecycle::is_present(size)) {
-    deprecate_warn0("3.4.0", "element_line(size)", "element_line(linewidth)")
-    linewidth <- size
+element_line <- S7::new_class(
+  "element_line", parent = element,
+  properties = element_props[c(
+    "colour", "linewidth", "linetype", "lineend", "linejoin",
+    "arrow", "arrow.fill",
+    "inherit.blank"
+  )],
+  constructor = function(colour = NULL, linewidth = NULL, linetype = NULL,
+                         lineend = NULL, color = NULL, linejoin = NULL,
+                         arrow = NULL, arrow.fill = NULL,
+                         inherit.blank = FALSE, size = deprecated()) {
+    if (lifecycle::is_present(size)) {
+      deprecate_warn0("3.4.0", "element_line(size)", "element_line(linewidth)")
+      linewidth <- size
+    }
+    colour <- color %||% colour
+    S7::new_object(
+      S7::S7_object(),
+      colour = colour,
+      linewidth = linewidth, linetype = linetype, lineend = lineend,
+      linejoin = linejoin,
+      arrow = arrow %||% FALSE,
+      arrow.fill = arrow.fill %||% colour,
+      inherit.blank = inherit.blank
+    )
   }
-
-  colour <- color %||% colour
-  arrow.fill <- arrow.fill %||% colour
-  arrow <- arrow %||% FALSE
-
-  structure(
-    list(colour = colour, linewidth = linewidth, linetype = linetype, lineend = lineend,
-      arrow = arrow, arrow.fill = arrow.fill, inherit.blank = inherit.blank),
-    class = c("element_line", "element")
-  )
-}
-
+)
 
 #' @param family Font family
 #' @param face Font face ("plain", "italic", "bold", "bold.italic")
@@ -145,116 +183,121 @@ element_line <- function(colour = NULL, linewidth = NULL, linetype = NULL,
 #'   is anchored.
 #' @export
 #' @rdname element
-element_text <- function(family = NULL, face = NULL, colour = NULL,
-  size = NULL, hjust = NULL, vjust = NULL, angle = NULL, lineheight = NULL,
-  color = NULL, margin = NULL, debug = NULL, inherit.blank = FALSE) {
-
-  if (!is.null(color))  colour <- color
-
-  n <- max(
-    length(family), length(face), length(colour), length(size),
-    length(hjust), length(vjust), length(angle), length(lineheight)
-  )
-  if (n > 1) {
-    cli::cli_warn(c(
-      "Vectorized input to {.fn element_text} is not officially supported.",
-      "i" = "Results may be unexpected or may change in future versions of ggplot2."
-    ))
-  }
-
-
-  structure(
-    list(family = family, face = face, colour = colour, size = size,
+element_text <- S7::new_class(
+  "element_text", parent = element,
+  properties = element_props[c(
+    "family", "face", "colour", "size", "hjust", "vjust", "angle", "lineheight",
+    "margin", "debug", "inherit.blank"
+  )],
+  constructor = function(family = NULL, face = NULL, colour = NULL,
+                         size = NULL, hjust = NULL, vjust = NULL, angle = NULL,
+                         lineheight = NULL, color = NULL, margin = NULL,
+                         debug = NULL, inherit.blank = FALSE) {
+    n <- max(
+      length(family), length(face), length(colour), length(size),
+      length(hjust), length(vjust), length(angle), length(lineheight)
+    )
+    if (n > 1) {
+      cli::cli_warn(c(
+        "Vectorized input to {.fn element_text} is not officially supported.",
+        "i" = "Results may be unexpected or may change in future versions of ggplot2."
+      ))
+    }
+
+    colour <- color %||% colour
+    S7::new_object(
+      S7::S7_object(),
+      family = family, face = face, colour = colour, size = size,
       hjust = hjust, vjust = vjust, angle = angle, lineheight = lineheight,
-      margin = margin, debug = debug, inherit.blank = inherit.blank),
-    class = c("element_text", "element")
-  )
-}
-
-#' @export
-#' @param type For testing elements: the type of element to expect. One of
-#'   `"blank"`, `"rect"`, `"line"` or `"text"`.
-#' @rdname is_tests
-is_theme_element <- function(x, type = "any") {
-  switch(
-    type %||% "any",
-    any   = inherits(x, "element"),
-    rect  = inherits(x, "element_rect"),
-    line  = inherits(x, "element_line"),
-    text  = inherits(x, "element_text"),
-    blank = inherits(x, "element_blank"),
-    # TODO: ideally we accept more elements from extensions. We need to
-    # consider how this will work with S7 classes, where ggplot2 doesn't know
-    # about the extension's class objects.
-    FALSE
-  )
-}
+      margin = margin, debug = debug, inherit.blank = inherit.blank
+    )
+  }
+)
 
 #' @export
 #' @rdname element
-element_polygon <- function(fill = NULL, colour = NULL, linewidth = NULL,
-                            linetype = NULL, color = NULL,
-                            inherit.blank = FALSE) {
-  structure(
-    list(
+element_polygon <- S7::new_class(
+  "element_polygon", parent = element,
+  properties = element_props[c(
+    "fill", "colour", "linewidth", "linetype", "linejoin", "inherit.blank"
+  )],
+  constructor = function(fill = NULL, colour = NULL, linewidth = NULL,
+                         linetype = NULL, color = NULL, linejoin = NULL,
+                         inherit.blank = FALSE) {
+    colour <- color %||% colour
+    S7::new_object(
+      S7::S7_object(),
       fill = fill, colour = color %||% colour, linewidth = linewidth,
-      linetype = linetype, inherit.blank = inherit.blank
-    ),
-    class = c("element_polygon", "element")
-  )
-}
+      linetype = linetype, linejoin = linejoin, inherit.blank = inherit.blank
+    )
+  }
+)
 
 #' @export
 #' @rdname element
-element_point <- function(colour = NULL, shape = NULL, size = NULL, fill = NULL,
-                          stroke = NULL, color = NULL, inherit.blank = FALSE) {
-  structure(
-    list(
+element_point <- S7::new_class(
+  "element_point", parent = element,
+  properties = rename(
+    element_props[c(
+      "colour", "shape", "size", "fill", "linewidth", "inherit.blank"
+    )],
+    c("linewidth" = "stroke")
+  ),
+  constructor = function(colour = NULL, shape = NULL, size = NULL, fill = NULL,
+                         stroke = NULL, color = NULL, inherit.blank = FALSE) {
+    S7::new_object(
+      S7::S7_object(),
       colour = color %||% colour, fill = fill, shape = shape, size = size,
       stroke = stroke, inherit.blank = inherit.blank
-    ),
-    class = c("element_point", "element")
-  )
-}
+    )
+  }
+)
 
 #' @param ink Foreground colour.
 #' @param paper Background colour.
 #' @param accent Accent colour.
 #' @export
 #' @rdname element
-element_geom <- function(
-    # colours
-  ink = NULL, paper = NULL, accent = NULL,
-  # linewidth
-  linewidth = NULL, borderwidth = NULL,
-  # linetype
-  linetype = NULL, bordertype = NULL,
-  # text
-  family = NULL, fontsize = NULL,
-  # points
-  pointsize = NULL, pointshape = NULL,
-
-  colour = NULL, color = NULL, fill = NULL) {
-
-  if (!is.null(fontsize)) {
-    fontsize <- fontsize / .pt
-  }
-
-  structure(
-    list(
-      ink = ink,
-      paper = paper,
-      accent = accent,
+element_geom <- S7::new_class(
+  "element_geom", parent = element,
+  properties = list(
+    ink = element_props$colour,
+    paper = element_props$colour,
+    accent = element_props$colour,
+    linewidth = element_props$linewidth,
+    borderwidth = element_props$linewidth,
+    linetype = element_props$linetype,
+    bordertype = element_props$linetype,
+    family = element_props$family,
+    fontsize = element_props$size,
+    pointsize = element_props$size,
+    pointshape = element_props$shape,
+    colour = element_props$colour,
+    fill = element_props$fill
+  ),
+  constructor = function(
+    ink = NULL, paper = NULL, accent = NULL,
+    linewidth = NULL, borderwidth = NULL,
+    linetype = NULL, bordertype = NULL,
+    family = NULL, fontsize = NULL,
+    pointsize = NULL, pointshape = NULL,
+    colour = NULL, color = NULL, fill = NULL) {
+
+    if (!is.null(fontsize)) {
+      fontsize <- fontsize / .pt
+    }
+
+    S7::new_object(
+      S7::S7_object(),
+      ink = ink, paper = paper, accent = accent,
       linewidth = linewidth, borderwidth = borderwidth,
       linetype = linetype, bordertype = bordertype,
       family = family, fontsize = fontsize,
       pointsize = pointsize, pointshape = pointshape,
-      colour = color %||% colour,
-      fill = fill
-    ),
-    class = c("element_geom", "element")
-  )
-}
+      colour = color %||% colour, fill = fill
+    )
+  }
+)
 
 .default_geom_element <- element_geom(
   ink = "black", paper = "white", accent = "#3366FF",
@@ -268,6 +311,24 @@ element_geom <- function(
 #' @export
 print.element <- function(x, ...) utils::str(x)
 
+#' @export
+#' @param type For testing elements: the type of element to expect. One of
+#'   `"blank"`, `"rect"`, `"line"`, `"text"`, `"polygon"`, `"point"` or `"geom"`.
+#' @rdname is_tests
+is_theme_element <- function(x, type = "any") {
+  switch(
+    type %||% "any",
+    any     = S7::S7_inherits(x, element),
+    blank   = S7::S7_inherits(x, element_blank),
+    rect    = S7::S7_inherits(x, element_rect),
+    line    = S7::S7_inherits(x, element_line),
+    text    = S7::S7_inherits(x, element_text),
+    polygon = S7::S7_inherits(x, element_polygon),
+    point   = S7::S7_inherits(x, element_point),
+    geom    = S7::S7_inherits(x, element_geom),
+    FALSE
+  )
+}
 
 #' @param x A single number specifying size relative to parent element.
 #' @rdname element
@@ -276,6 +337,45 @@ rel <- function(x) {
   structure(x, class = "rel")
 }
 
+#' @export
+`$.ggplot2::element` <- function(x, i) {
+  # deprecate_soft0("4.1.0", I("`<ggplot2::element>$i`"), I("`<ggplot2::element>@i`"))
+  `[[`(S7::props(x), i)
+}
+
+#' @export
+`[.ggplot2::element` <- function(x, i) {
+  # deprecate_soft0("4.1.0", I("`<gglot2::element>[i]`"), I("`S7::props(<ggplot2::element>, i)`"))
+  `[`(S7::props(x), i)
+}
+
+#' @export
+`[[.ggplot2::element` <- function(x, i) {
+  # deprecate_soft0("4.1.0", I("`<ggplot2::element>[[i]]`"), I("`S7::prop(<ggplot2::element>, i)`"))
+  `[[`(S7::props(x), i)
+}
+
+#' @export
+`$<-.ggplot2::element` <- function(x, i, value) {
+  # deprecate_soft0("4.1.0", I("`<ggplot2::element>$i <- value`"), I("`<ggplot2::element>@i <- value`"))
+  S7::props(x) <- `[[<-`(S7::props(x), i, value)
+  x
+}
+
+#' @export
+`[<-.ggplot2::element` <- function(x, i, value) {
+  # deprecate_soft0("4.1.0", I("`<ggplot2::element>[i] <- value`"), I("`S7::props(<ggplot2::element>)[i] <- value`"))
+  S7::props(x) <- `[<-`(S7::props(x), i, value)
+  x
+}
+
+#' @export
+`[[<-.ggplot2::element` <- function(x, i, value) {
+  # deprecate_soft0("4.1.0", I("`<ggplot2::element>[[i]] <- value`"), I("S7::prop(<ggplot2::element>, i) <- value"))
+  S7::props(x) <- `[[<-`(S7::props(x), i, value)
+  x
+}
+
 #' @export
 print.rel <- function(x, ...) print(noquote(paste(x, " *", sep = "")))
 
@@ -314,134 +414,131 @@ element_render <- function(theme, element, ..., name = NULL) {
 #'   usually at least position. See the source code for individual methods.
 #' @keywords internal
 #' @export
-element_grob <- function(element, ...) {
-  UseMethod("element_grob")
-}
-
-#' @export
-element_grob.element_blank <- function(element, ...)  zeroGrob()
-
-#' @export
-element_grob.element_rect <- function(element, x = 0.5, y = 0.5,
-  width = 1, height = 1,
-  fill = NULL, colour = NULL, linewidth = NULL, linetype = NULL, ..., size = deprecated()) {
+element_grob <- S7::new_generic("element_grob", "element")
 
-  if (lifecycle::is_present(size)) {
-    deprecate_warn0("3.4.0", "element_grob.element_rect(size)", "element_grob.element_rect(linewidth)")
-    linewidth <- size
-  }
+S7::method(element_grob, element_blank) <- function(element, ...) zeroGrob()
 
-  # The gp settings can override element_gp
-  gp <- gg_par(lwd = linewidth, col = colour, fill = fill, lty = linetype)
-  element_gp <- gg_par(lwd = element$linewidth, col = element$colour,
-    fill = element$fill, lty = element$linetype)
+S7::method(element_grob, element_rect) <-
+  function(element, x = 0.5, y = 0.5, width = 1, height = 1,
+           fill = NULL, colour = NULL,
+           linewidth = NULL, linetype = NULL, linejoin = NULL,
+           ..., size = deprecated()) {
 
-  rectGrob(x, y, width, height, gp = modify_list(element_gp, gp), ...)
-}
+    if (lifecycle::is_present(size)) {
+      deprecate_warn0("3.4.0", "element_grob.element_rect(size)", "element_grob.element_rect(linewidth)")
+      linewidth <- size
+    }
 
+    gp <- gg_par(lwd = linewidth, col = colour, fill = fill, lty = linetype, linejoin = linejoin)
+    element_gp <- gg_par(lwd = element@linewidth, col = element@colour,
+                         fill = element@fill, lty = element@linetype,
+                         linejoin = element@linejoin)
 
-#' @export
-element_grob.element_text <- function(element, label = "", x = NULL, y = NULL,
-  family = NULL, face = NULL, colour = NULL, size = NULL,
-  hjust = NULL, vjust = NULL, angle = NULL, lineheight = NULL,
-  margin = NULL, margin_x = FALSE, margin_y = FALSE, ...) {
+    rectGrob(x, y, width, height, gp = modify_list(element_gp, gp), ...)
+  }
 
-  if (is.null(label))
-    return(zeroGrob())
+S7::method(element_grob, element_text) <-
+  function(element, label = "", x = NULL, y = NULL,
+           family = NULL, face = NULL, colour = NULL, size = NULL,
+           hjust = NULL, vjust = NULL, angle = NULL, lineheight = NULL,
+           margin = NULL, margin_x = FALSE, margin_y = FALSE, ...) {
 
-  vj <- vjust %||% element$vjust
-  hj <- hjust %||% element$hjust
-  margin <- margin %||% element$margin
+    if (is.null(label))
+      return(zeroGrob())
 
-  angle <- angle %||% element$angle %||% 0
+    vj <- vjust %||% element@vjust
+    hj <- hjust %||% element@hjust
+    margin <- margin %||% element@margin
 
-  # The gp settings can override element_gp
-  gp <- gg_par(fontsize = size, col = colour,
-    fontfamily = family, fontface = face,
-    lineheight = lineheight)
-  element_gp <- gg_par(fontsize = element$size, col = element$colour,
-    fontfamily = element$family, fontface = element$face,
-    lineheight = element$lineheight)
+    angle <- angle %||% element@angle %||% 0
 
-  titleGrob(label, x, y, hjust = hj, vjust = vj, angle = angle,
-    gp = modify_list(element_gp, gp), margin = margin,
-    margin_x = margin_x, margin_y = margin_y, debug = element$debug, ...)
-}
+    # The gp settings can override element_gp
+    gp <- gg_par(fontsize = size, col = colour,
+                 fontfamily = family, fontface = face,
+                 lineheight = lineheight)
+    element_gp <- gg_par(fontsize = element@size, col = element@colour,
+                         fontfamily = element@family, fontface = element@face,
+                         lineheight = element@lineheight)
 
+    titleGrob(label, x, y, hjust = hj, vjust = vj, angle = angle,
+              gp = modify_list(element_gp, gp), margin = margin,
+              margin_x = margin_x, margin_y = margin_y, debug = element@debug, ...)
+  }
 
+S7::method(element_grob, element_line) <-
+  function(element, x = 0:1, y = 0:1,
+           colour = NULL, linewidth = NULL, linetype = NULL, lineend = NULL,
+           linejoin = NULL, arrow.fill = NULL,
+           default.units = "npc", id.lengths = NULL, ..., size = deprecated()) {
+
+    if (lifecycle::is_present(size)) {
+      deprecate_warn0("3.4.0", "element_grob.element_line(size)", "element_grob.element_line(linewidth)")
+      linewidth <- size
+    }
+
+    arrow <- if (is.logical(element@arrow) && !element@arrow) {
+      NULL
+    } else {
+      element@arrow
+    }
+    if (is.null(arrow)) {
+      arrow.fill <- colour
+      element@arrow.fill <- element@colour
+    }
+
+    # The gp settings can override element_gp
+    gp <- gg_par(
+      col = colour, fill = arrow.fill %||% colour,
+      lwd = linewidth, lty = linetype, lineend = lineend, linejoin = linejoin
+    )
+    element_gp <- gg_par(
+      col = element@colour, fill = element@arrow.fill %||% element@colour,
+      lwd = element@linewidth, lty = element@linetype,
+      lineend = element@lineend, linejoin = element@linejoin
+    )
 
-#' @export
-element_grob.element_line <- function(element, x = 0:1, y = 0:1,
-  colour = NULL, linewidth = NULL, linetype = NULL, lineend = NULL,
-  arrow.fill = NULL,
-  default.units = "npc", id.lengths = NULL, ..., size = deprecated()) {
-
-  if (lifecycle::is_present(size)) {
-    deprecate_warn0("3.4.0", "element_grob.element_line(size)", "element_grob.element_line(linewidth)")
-    linewidth <- size
+    polylineGrob(
+      x, y, default.units = default.units,
+      gp = modify_list(element_gp, gp),
+      id.lengths = id.lengths, arrow = arrow, ...
+    )
   }
 
-  arrow <- if (is.logical(element$arrow) && !element$arrow) {
-    NULL
-  } else {
-    element$arrow
-  }
-  if (is.null(arrow)) {
-    arrow.fill <- colour
-    element$arrow.fill <- element$colour
+S7::method(element_grob, element_polygon) <-
+  function(element, x = c(0, 0.5, 1, 0.5),
+           y = c(0.5, 1, 0.5, 0), fill = NULL,
+           colour = NULL, linewidth = NULL,
+           linetype = NULL, linejoin = NULL, ...,
+           id = NULL, id.lengths = NULL,
+           pathId = NULL, pathId.lengths = NULL) {
+
+    gp <- gg_par(lwd = linewidth, col = colour, fill = fill,
+                 lty = linetype, linejoin = linejoin)
+    element_gp <- gg_par(lwd = element@linewidth, col = element@colour,
+                         fill = element@fill, lty = element@linetype,
+                         linejoin = element@linejoin)
+    pathGrob(
+      x = x, y = y, gp = modify_list(element_gp, gp), ...,
+      # We swap the id logic so that `id` is always the (super)group id
+      # (consistent with `polygonGrob()`) and `pathId` always the subgroup id.
+      pathId = id, pathId.lengths = id.lengths,
+      id = pathId, id.lengths = pathId.lengths
+    )
   }
 
-  # The gp settings can override element_gp
-  gp <- gg_par(
-    col = colour, fill = arrow.fill %||% colour,
-    lwd = linewidth, lty = linetype, lineend = lineend
-  )
-  element_gp <- gg_par(
-    col = element$colour, fill = element$arrow.fill %||% element$colour,
-    lwd = element$linewidth, lty = element$linetype,
-    lineend = element$lineend
-  )
-
-  polylineGrob(
-    x, y, default.units = default.units,
-    gp = modify_list(element_gp, gp),
-    id.lengths = id.lengths, arrow = arrow, ...
-  )
-}
-
-#' @export
-element_grob.element_polygon <- function(element, x = c(0, 0.5, 1, 0.5),
-                                         y = c(0.5, 1, 0.5, 0), fill = NULL,
-                                         colour = NULL, linewidth = NULL,
-                                         linetype = NULL, ...,
-                                         id = NULL, id.lengths = NULL,
-                                         pathId = NULL, pathId.lengths = NULL) {
-
-  gp <- gg_par(lwd = linewidth, col = colour, fill = fill, lty = linetype)
-  element_gp <- gg_par(lwd = element$linewidth, col = element$colour,
-                       fill = element$fill, lty = element$linetype)
-  pathGrob(
-    x = x, y = y, gp = modify_list(element_gp, gp), ...,
-    # We swap the id logic so that `id` is always the (super)group id
-    # (consistent with `polygonGrob()`) and `pathId` always the subgroup id.
-    pathId = id, pathId.lengths = id.lengths,
-    id = pathId, id.lengths = pathId.lengths
-  )
-}
-
-#' @export
-element_grob.element_point <- function(element, x = 0.5, y = 0.5, colour = NULL,
-                                       shape = NULL, fill = NULL, size = NULL,
-                                       stroke = NULL, ...,
-                                       default.units = "npc") {
-
-  gp <- gg_par(col = colour, fill = fill, pointsize = size, stroke = stroke)
-  element_gp <- gg_par(col = element$colour, fill = element$fill,
-                       pointsize = element$size, stroke = element$stroke)
-  shape <- translate_shape_string(shape %||% element$shape %||% 19)
-  pointsGrob(x = x, y = y, pch = shape, gp = modify_list(element_gp, gp),
-             default.units = default.units, ...)
-}
+S7::method(element_grob, element_point) <-
+  function(element, x = 0.5, y = 0.5, colour = NULL,
+           shape = NULL, fill = NULL, size = NULL,
+           stroke = NULL, ...,
+           default.units = "npc") {
+
+    gp <- gg_par(col = colour, fill = fill, pointsize = size, stroke = stroke)
+    element_gp <- gg_par(col = element@colour, fill = element@fill,
+                         pointsize = element@size, stroke = element@stroke)
+    shape <- translate_shape_string(shape %||% element@shape %||% 19)
+    pointsGrob(x = x, y = y, pch = shape, gp = modify_list(element_gp, gp),
+               default.units = default.units, ...)
+  }
 
 #' Define and register new theme elements
 #'
@@ -476,7 +573,7 @@ element_grob.element_point <- function(element, x = 0.5, y = 0.5, colour = NULL,
 #' # plot panels. To do so, it registers a new theme element `ggxyz.panel.annotation`
 #' register_theme_elements(
 #'   ggxyz.panel.annotation = element_text(color = "blue", hjust = 0.95, vjust = 0.05),
-#'   element_tree = list(ggxyz.panel.annotation = el_def("element_text", "text"))
+#'   element_tree = list(ggxyz.panel.annotation = el_def(element_text, "text"))
 #' )
 #'
 #' # Now the package can define a new coord that includes a panel annotation
@@ -595,8 +692,8 @@ check_element_tree <- function(x, arg = caller_arg(x), call = caller_env()) {
 #' @details
 #' The function `el_def()` is used to define new or modified element types and
 #' element inheritance relationships for the element tree.
-#' @param class The name of the element class. Examples are "element_line" or
-#'  "element_text" or "unit", or one of the two reserved keywords "character" or
+#' @param class The name of the element class. Examples are `element_line` or
+#'  `element_text` or "unit", or one of the two reserved keywords "character" or
 #'  "margin". The reserved keyword "character" implies a character
 #'  or numeric vector, not a class called "character". The keyword
 #'  "margin" implies a unit vector of length 4, as created by [margin()].
@@ -607,6 +704,27 @@ check_element_tree <- function(x, arg = caller_arg(x), call = caller_env()) {
 #' @keywords internal
 #' @export
 el_def <- function(class = NULL, inherit = NULL, description = NULL) {
+  if (is.character(class) && length(class) == 1) {
+    # Swap S3 class name for S7 class object
+    class <- switch(
+      class,
+      element = element,
+      element_blank   = element_blank,
+      element_rect    = element_rect,
+      element_line    = element_line,
+      element_text    = element_text,
+      element_polygon = element_polygon,
+      element_point   = element_point,
+      element_geom    = element_geom,
+      margin          = margin,
+      class
+    )
+  }
+  # margins often occur in c("unit", "margin", "rel"), we cannot use the
+  # S7 class here because we don't support heterogeneous lists
+  if (is.character(class) && length(class) > 1) {
+    class[class == "margin"] <- "ggplot2::margin"
+  }
   list(class = class, inherit = inherit, description = description)
 }
 
@@ -615,43 +733,43 @@ el_def <- function(class = NULL, inherit = NULL, description = NULL) {
 # among them. It should not be read from directly, since users may modify the
 # current element tree stored in ggplot_global$element_tree
 .element_tree <- list(
-  line                = el_def("element_line"),
-  rect                = el_def("element_rect"),
-  text                = el_def("element_text"),
-  point               = el_def("element_point"),
-  polygon             = el_def("element_polygon"),
-  geom                = el_def("element_geom"),
-  title               = el_def("element_text", "text"),
+  line                = el_def(element_line),
+  rect                = el_def(element_rect),
+  text                = el_def(element_text),
+  point               = el_def(element_point),
+  polygon             = el_def(element_polygon),
+  geom                = el_def(element_geom),
+  title               = el_def(element_text, "text"),
   spacing             = el_def("unit"),
   margins             = el_def(c("margin", "unit")),
 
-  axis.line           = el_def("element_line", "line"),
-  axis.text           = el_def("element_text", "text"),
-  axis.title          = el_def("element_text", "title"),
-  axis.ticks          = el_def("element_line", "line"),
+  axis.line           = el_def(element_line, "line"),
+  axis.text           = el_def(element_text, "text"),
+  axis.title          = el_def(element_text, "title"),
+  axis.ticks          = el_def(element_line, "line"),
   legend.key.size     = el_def(c("unit", "rel"), "spacing"),
-  panel.grid          = el_def("element_line", "line"),
-  panel.grid.major    = el_def("element_line", "panel.grid"),
-  panel.grid.minor    = el_def("element_line", "panel.grid"),
-  strip.text          = el_def("element_text", "text"),
-
-  axis.line.x         = el_def("element_line", "axis.line"),
-  axis.line.x.top     = el_def("element_line", "axis.line.x"),
-  axis.line.x.bottom  = el_def("element_line", "axis.line.x"),
-  axis.line.y         = el_def("element_line", "axis.line"),
-  axis.line.y.left    = el_def("element_line", "axis.line.y"),
-  axis.line.y.right   = el_def("element_line", "axis.line.y"),
-  axis.line.theta     = el_def("element_line", "axis.line.x"),
-  axis.line.r         = el_def("element_line", "axis.line.y"),
-
-  axis.text.x         = el_def("element_text", "axis.text"),
-  axis.text.x.top     = el_def("element_text", "axis.text.x"),
-  axis.text.x.bottom  = el_def("element_text", "axis.text.x"),
-  axis.text.y         = el_def("element_text", "axis.text"),
-  axis.text.y.left    = el_def("element_text", "axis.text.y"),
-  axis.text.y.right   = el_def("element_text", "axis.text.y"),
-  axis.text.theta     = el_def("element_text", "axis.text.x"),
-  axis.text.r         = el_def("element_text", "axis.text.y"),
+  panel.grid          = el_def(element_line, "line"),
+  panel.grid.major    = el_def(element_line, "panel.grid"),
+  panel.grid.minor    = el_def(element_line, "panel.grid"),
+  strip.text          = el_def(element_text, "text"),
+
+  axis.line.x         = el_def(element_line, "axis.line"),
+  axis.line.x.top     = el_def(element_line, "axis.line.x"),
+  axis.line.x.bottom  = el_def(element_line, "axis.line.x"),
+  axis.line.y         = el_def(element_line, "axis.line"),
+  axis.line.y.left    = el_def(element_line, "axis.line.y"),
+  axis.line.y.right   = el_def(element_line, "axis.line.y"),
+  axis.line.theta     = el_def(element_line, "axis.line.x"),
+  axis.line.r         = el_def(element_line, "axis.line.y"),
+
+  axis.text.x         = el_def(element_text, "axis.text"),
+  axis.text.x.top     = el_def(element_text, "axis.text.x"),
+  axis.text.x.bottom  = el_def(element_text, "axis.text.x"),
+  axis.text.y         = el_def(element_text, "axis.text"),
+  axis.text.y.left    = el_def(element_text, "axis.text.y"),
+  axis.text.y.right   = el_def(element_text, "axis.text.y"),
+  axis.text.theta     = el_def(element_text, "axis.text.x"),
+  axis.text.r         = el_def(element_text, "axis.text.y"),
 
   axis.ticks.length   = el_def(c("unit", "rel"), "spacing"),
   axis.ticks.length.x = el_def(c("unit", "rel"), "axis.ticks.length"),
@@ -663,28 +781,28 @@ el_def <- function(class = NULL, inherit = NULL, description = NULL) {
   axis.ticks.length.theta = el_def(c("unit", "rel"), "axis.ticks.length.x"),
   axis.ticks.length.r = el_def(c("unit", "rel"), "axis.ticks.length.y"),
 
-  axis.ticks.x        = el_def("element_line", "axis.ticks"),
-  axis.ticks.x.top    = el_def("element_line", "axis.ticks.x"),
-  axis.ticks.x.bottom = el_def("element_line", "axis.ticks.x"),
-  axis.ticks.y        = el_def("element_line", "axis.ticks"),
-  axis.ticks.y.left   = el_def("element_line", "axis.ticks.y"),
-  axis.ticks.y.right  = el_def("element_line", "axis.ticks.y"),
-  axis.ticks.theta    = el_def("element_line", "axis.ticks.x"),
-  axis.ticks.r        = el_def("element_line", "axis.ticks.y"),
-
-  axis.title.x        = el_def("element_text", "axis.title"),
-  axis.title.x.top    = el_def("element_text", "axis.title.x"),
-  axis.title.x.bottom = el_def("element_text", "axis.title.x"),
-  axis.title.y        = el_def("element_text", "axis.title"),
-  axis.title.y.left   = el_def("element_text", "axis.title.y"),
-  axis.title.y.right  = el_def("element_text", "axis.title.y"),
-
-  axis.minor.ticks.x.top    = el_def("element_line", "axis.ticks.x.top"),
-  axis.minor.ticks.x.bottom = el_def("element_line", "axis.ticks.x.bottom"),
-  axis.minor.ticks.y.left   = el_def("element_line", "axis.ticks.y.left"),
-  axis.minor.ticks.y.right  = el_def("element_line", "axis.ticks.y.right"),
-  axis.minor.ticks.theta    = el_def("element_line", "axis.ticks.theta"),
-  axis.minor.ticks.r        = el_def("element_line", "axis.ticks.r"),
+  axis.ticks.x        = el_def(element_line, "axis.ticks"),
+  axis.ticks.x.top    = el_def(element_line, "axis.ticks.x"),
+  axis.ticks.x.bottom = el_def(element_line, "axis.ticks.x"),
+  axis.ticks.y        = el_def(element_line, "axis.ticks"),
+  axis.ticks.y.left   = el_def(element_line, "axis.ticks.y"),
+  axis.ticks.y.right  = el_def(element_line, "axis.ticks.y"),
+  axis.ticks.theta    = el_def(element_line, "axis.ticks.x"),
+  axis.ticks.r        = el_def(element_line, "axis.ticks.y"),
+
+  axis.title.x        = el_def(element_text, "axis.title"),
+  axis.title.x.top    = el_def(element_text, "axis.title.x"),
+  axis.title.x.bottom = el_def(element_text, "axis.title.x"),
+  axis.title.y        = el_def(element_text, "axis.title"),
+  axis.title.y.left   = el_def(element_text, "axis.title.y"),
+  axis.title.y.right  = el_def(element_text, "axis.title.y"),
+
+  axis.minor.ticks.x.top    = el_def(element_line, "axis.ticks.x.top"),
+  axis.minor.ticks.x.bottom = el_def(element_line, "axis.ticks.x.bottom"),
+  axis.minor.ticks.y.left   = el_def(element_line, "axis.ticks.y.left"),
+  axis.minor.ticks.y.right  = el_def(element_line, "axis.ticks.y.right"),
+  axis.minor.ticks.theta    = el_def(element_line, "axis.ticks.theta"),
+  axis.minor.ticks.r        = el_def(element_line, "axis.ticks.r"),
 
   axis.minor.ticks.length = el_def(c("unit", "rel")),
   axis.minor.ticks.length.x = el_def(c("unit", "rel"), "axis.minor.ticks.length"),
@@ -708,25 +826,25 @@ el_def <- function(class = NULL, inherit = NULL, description = NULL) {
     c("unit", "rel"), c("axis.minor.ticks.length.y", "axis.ticks.length.r")
   ),
 
-  legend.background   = el_def("element_rect", "rect"),
+  legend.background   = el_def(element_rect, "rect"),
   legend.margin       = el_def(c("margin", "unit", "rel"), "margins"),
   legend.spacing      = el_def(c("unit", "rel"), "spacing"),
   legend.spacing.x     = el_def(c("unit", "rel"), "legend.spacing"),
   legend.spacing.y     = el_def(c("unit", "rel"), "legend.spacing"),
-  legend.key          = el_def("element_rect", "panel.background"),
+  legend.key          = el_def(element_rect, "panel.background"),
   legend.key.height   = el_def(c("unit", "rel"), "legend.key.size"),
   legend.key.width    = el_def(c("unit", "rel"), "legend.key.size"),
   legend.key.spacing  = el_def(c("unit", "rel"), "spacing"),
   legend.key.spacing.x = el_def(c("unit", "rel"), "legend.key.spacing"),
   legend.key.spacing.y = el_def(c("unit", "rel"), "legend.key.spacing"),
   legend.key.justification = el_def(c("character", "numeric", "integer")),
-  legend.frame        = el_def("element_rect", "rect"),
-  legend.axis.line    = el_def("element_line", "line"),
-  legend.ticks        = el_def("element_line", "legend.axis.line"),
+  legend.frame        = el_def(element_rect, "rect"),
+  legend.axis.line    = el_def(element_line, "line"),
+  legend.ticks        = el_def(element_line, "legend.axis.line"),
   legend.ticks.length = el_def(c("rel", "unit"), "legend.key.size"),
-  legend.text         = el_def("element_text", "text"),
+  legend.text         = el_def(element_text, "text"),
   legend.text.position = el_def("character"),
-  legend.title        = el_def("element_text", "title"),
+  legend.title        = el_def(element_text, "title"),
   legend.title.position = el_def("character"),
   legend.byrow        = el_def("logical"),
   legend.position     = el_def("character"),
@@ -760,45 +878,45 @@ el_def <- function(class = NULL, inherit = NULL, description = NULL) {
   legend.box          = el_def("character"),
   legend.box.just     = el_def("character"),
   legend.box.margin   = el_def(c("margin", "unit", "rel"), "margins"),
-  legend.box.background = el_def("element_rect", "rect"),
+  legend.box.background = el_def(element_rect, "rect"),
   legend.box.spacing  = el_def(c("unit", "rel"), "spacing"),
 
-  panel.background    = el_def("element_rect", "rect"),
-  panel.border        = el_def("element_rect", "rect"),
+  panel.background    = el_def(element_rect, "rect"),
+  panel.border        = el_def(element_rect, "rect"),
   panel.spacing       = el_def(c("unit", "rel"), "spacing"),
   panel.spacing.x     = el_def(c("unit", "rel"), "panel.spacing"),
   panel.spacing.y     = el_def(c("unit", "rel"), "panel.spacing"),
-  panel.grid.major.x  = el_def("element_line", "panel.grid.major"),
-  panel.grid.major.y  = el_def("element_line", "panel.grid.major"),
-  panel.grid.minor.x  = el_def("element_line", "panel.grid.minor"),
-  panel.grid.minor.y  = el_def("element_line", "panel.grid.minor"),
+  panel.grid.major.x  = el_def(element_line, "panel.grid.major"),
+  panel.grid.major.y  = el_def(element_line, "panel.grid.major"),
+  panel.grid.minor.x  = el_def(element_line, "panel.grid.minor"),
+  panel.grid.minor.y  = el_def(element_line, "panel.grid.minor"),
   panel.ontop         = el_def("logical"),
   panel.widths        = el_def("unit"),
   panel.heights       = el_def("unit"),
 
-  strip.background    = el_def("element_rect", "rect"),
-  strip.background.x  = el_def("element_rect", "strip.background"),
-  strip.background.y  = el_def("element_rect", "strip.background"),
+  strip.background    = el_def(element_rect, "rect"),
+  strip.background.x  = el_def(element_rect, "strip.background"),
+  strip.background.y  = el_def(element_rect, "strip.background"),
   strip.clip          = el_def("character"),
-  strip.text.x        = el_def("element_text", "strip.text"),
-  strip.text.x.top    = el_def("element_text", "strip.text.x"),
-  strip.text.x.bottom = el_def("element_text", "strip.text.x"),
-  strip.text.y        = el_def("element_text", "strip.text"),
-  strip.text.y.left   = el_def("element_text", "strip.text.y"),
-  strip.text.y.right  = el_def("element_text", "strip.text.y"),
+  strip.text.x        = el_def(element_text, "strip.text"),
+  strip.text.x.top    = el_def(element_text, "strip.text.x"),
+  strip.text.x.bottom = el_def(element_text, "strip.text.x"),
+  strip.text.y        = el_def(element_text, "strip.text"),
+  strip.text.y.left   = el_def(element_text, "strip.text.y"),
+  strip.text.y.right  = el_def(element_text, "strip.text.y"),
   strip.placement     = el_def("character"),
   strip.placement.x   = el_def("character", "strip.placement"),
   strip.placement.y   = el_def("character", "strip.placement"),
   strip.switch.pad.grid = el_def(c("unit", "rel"), "spacing"),
   strip.switch.pad.wrap = el_def(c("unit", "rel"), "spacing"),
 
-  plot.background     = el_def("element_rect", "rect"),
-  plot.title          = el_def("element_text", "title"),
+  plot.background     = el_def(element_rect, "rect"),
+  plot.title          = el_def(element_text, "title"),
   plot.title.position = el_def("character"),
-  plot.subtitle       = el_def("element_text", "text"),
-  plot.caption        = el_def("element_text", "text"),
+  plot.subtitle       = el_def(element_text, "text"),
+  plot.caption        = el_def(element_text, "text"),
   plot.caption.position = el_def("character"),
-  plot.tag            = el_def("element_text", "text"),
+  plot.tag            = el_def(element_text, "text"),
   plot.tag.position   = el_def(c("character", "numeric", "integer")),  # Need to also accept numbers
   plot.tag.location   = el_def("character"),
   plot.margin         = el_def(c("margin", "unit", "rel"), "margins"),
@@ -843,11 +961,35 @@ check_element <- function(el, elname, element_tree, call = caller_env()) {
   # NULL values for elements are OK
   if (is.null(el)) return()
 
-  if ("margin" %in% eldef$class) {
-    if (!is.unit(el) && length(el) == 4)
-      cli::cli_abort("The {.var {elname}} theme element must be a {.cls unit} vector of length 4.", call = call)
-  } else if (!inherits(el, eldef$class) && !inherits(el, "element_blank")) {
-    cli::cli_abort("The {.var {elname}} theme element must be a {.cls {eldef$class}} object.", call = call)
+  class <- eldef$class
+  if (inherits(class, "S7_class")) {
+    inherit_ok <- S7::S7_inherits(el, class)
+  } else {
+    inherit_ok <- inherits(el, class)
+  }
+
+  if (is.character(class) && any(c("margin", "ggplot2::margin") %in% class)) {
+    if ("rel" %in% class && is.rel(el)) {
+      return()
+    }
+    if (is.unit(el) && length(el) == 4) {
+      return()
+    }
+    cli::cli_abort(
+      "The {.var {elname}} theme element must be a {.cls unit} vector of length 4",
+      call = call
+    )
+  }
+
+  # Maybe we should check that `class` is an element class before approving of
+  # blank elements?
+  if (inherit_ok || is_theme_element(el, "blank")) {
+    return()
   }
-  invisible()
+
+  class_name <- if (inherits(class, "S7_class")) class@name else class
+  cli::cli_abort(
+    "The {.var {elname}} theme element must be a {.cls {class_name}} object.",
+    call = call
+  )
 }
diff --git a/R/theme.R b/R/theme.R
index 471d030882..5f5121d4fd 100644
--- a/R/theme.R
+++ b/R/theme.R
@@ -217,7 +217,7 @@
 #' @param validate `TRUE` to run `check_element()`, `FALSE` to bypass checks.
 #' @export
 #' @seealso
-#'   [+.gg()] and [%+replace%],
+#'   [add_gg()] and [%+replace%],
 #'   [element_blank()], [element_line()],
 #'   [element_rect()], and [element_text()] for
 #'   details of the specific theme elements.
@@ -475,8 +475,8 @@ theme <- function(...,
   # If complete theme set all non-blank elements to inherit from blanks
   if (complete) {
     elements <- lapply(elements, function(el) {
-      if (is_theme_element(el) && !is_theme_element(el, "blank")) {
-        el$inherit.blank <- TRUE
+      if (is_theme_element(el) && S7::prop_exists(el, "inherit.blank")) {
+        S7::prop(el, "inherit.blank") <- TRUE
       }
       el
     })
@@ -744,7 +744,7 @@ calc_element <- function(element, theme, verbose = FALSE, skip_blank = FALSE,
 
   # If result is element_blank, we skip it if `skip_blank` is `TRUE`,
   # and otherwise we don't inherit anything from parents
-  if (inherits(el_out, "element_blank")) {
+  if (is_theme_element(el_out, "blank")) {
     if (isTRUE(skip_blank)) {
       el_out <- NULL
     } else {
@@ -758,9 +758,17 @@ calc_element <- function(element, theme, verbose = FALSE, skip_blank = FALSE,
 
   # If the element is defined (and not just inherited), check that
   # it is of the class specified in element_tree
-  if (!is.null(el_out) &&
-      !inherits(el_out, element_tree[[element]]$class)) {
-    cli::cli_abort("Theme element {.var {element}} must have class {.cls {ggplot_global$element_tree[[element]]$class}}.", call = call)
+  if (!is.null(el_out)) {
+    class <- element_tree[[element]]$class
+    if (inherits(class, "S7_class")) {
+      if (!S7::S7_inherits(el_out, class)) {
+        cli::cli_abort("Theme element {.var {element}} must have class {.cls {class@name}}.", call = call)
+      }
+    } else {
+      if (!inherits(el_out, class)) {
+        cli::cli_abort("Theme element {.var {element}} must have class {.cls {ggplot_global$element_tree[[element]]$class}}.", call = call)
+      }
+    }
   }
 
   # Get the names of parents from the inheritance tree
@@ -771,15 +779,23 @@ calc_element <- function(element, theme, verbose = FALSE, skip_blank = FALSE,
     if (verbose) cli::cli_inform("nothing (top level)")
 
     # Check that all the properties of this element are non-NULL
-    nullprops <- vapply(el_out, is.null, logical(1))
+    if (is_theme_element(el_out)) {
+      nullprops <- lengths(S7::props(el_out)) == 0
+    } else {
+      nullprops <- vapply(el_out, is.null, logical(1))
+    }
     if (!any(nullprops)) {
       return(el_out) # no null properties, return element as is
     }
 
     # if we have null properties, try to fill in from ggplot_global$theme_default
     el_out <- combine_elements(el_out, ggplot_global$theme_default[[element]])
-    nullprops <- vapply(el_out, is.null, logical(1))
-    if (inherits(el_out, "element_geom")) {
+    if (is_theme_element(el_out)) {
+      nullprops <- lengths(S7::props(el_out)) == 0
+    } else {
+      nullprops <- vapply(el_out, is.null, logical(1))
+    }
+    if (is_theme_element(el_out, "geom")) {
       # Geom elements are expected to have NULL fill/colour, so allow these
       # to be missing
       nullprops[c("colour", "fill")] <- FALSE
@@ -793,15 +809,19 @@ calc_element <- function(element, theme, verbose = FALSE, skip_blank = FALSE,
 
   # Calculate the parent objects' inheritance
   if (verbose) cli::cli_inform("{pnames}")
+
+  # once we've started skipping blanks, we continue doing so until the end of the
+  # recursion; we initiate skipping blanks if we encounter an element that
+  # doesn't inherit blank.
+  skip_blank <- skip_blank ||
+    (!is.null(el_out) && !isTRUE(try_prop(el_out, "inherit.blank")))
+
   parents <- lapply(
     pnames,
     calc_element,
     theme,
     verbose = verbose,
-    # once we've started skipping blanks, we continue doing so until the end of the
-    # recursion; we initiate skipping blanks if we encounter an element that
-    # doesn't inherit blank.
-    skip_blank = skip_blank || (!is.null(el_out) && !isTRUE(el_out$inherit.blank)),
+    skip_blank = skip_blank,
     call = call
   )
 
@@ -827,69 +847,63 @@ calc_element <- function(element, theme, verbose = FALSE, skip_blank = FALSE,
 #' # Adopt size but ignore colour
 #' merge_element(new, old)
 #'
-merge_element <- function(new, old) {
-  UseMethod("merge_element")
-}
+merge_element <- S7::new_generic("merge_element", c("new", "old"))
+
+S7::method(merge_element, list(S7::class_any, S7::class_any))  <-
+  function(new, old, ...) {
+    if (is.null(old) || is_theme_element(old, "blank")) {
+      # If old is NULL or element_blank, then just return new
+      return(new)
+    } else if (is.null(new) || is.character(new) || is.numeric(new) || is.unit(new) ||
+               is.logical(new) || is.function(new)) {
+      # If new is NULL, or a string, numeric vector, unit, or logical, just return it
+      return(new)
+    }
 
-#' @rdname merge_element
-#' @export
-merge_element.default <- function(new, old) {
-  if (is.null(old) || inherits(old, "element_blank")) {
-    # If old is NULL or element_blank, then just return new
-    return(new)
-  } else if (is.null(new) || is.character(new) || is.numeric(new) || is.unit(new) ||
-             is.logical(new) || is.function(new)) {
-    # If new is NULL, or a string, numeric vector, unit, or logical, just return it
-    return(new)
+    # otherwise we can't merge
+    cli::cli_abort("No method for merging {.cls {class(new)[1]}} into {.cls {class(old)[1]}}.")
   }
 
-  # otherwise we can't merge
-  cli::cli_abort("No method for merging {.cls {class(new)[1]}} into {.cls {class(old)[1]}}.")
-}
-
-#' @rdname merge_element
-#' @export
-merge_element.element_blank <- function(new, old) {
-  # If new is element_blank, just return it
-  new
-}
-
-#' @rdname merge_element
-#' @export
-merge_element.element <- function(new, old) {
-  if (is.null(old) || inherits(old, "element_blank")) {
-    # If old is NULL or element_blank, then just return new
-    return(new)
+S7::method(merge_element, list(element_blank, S7::class_any)) <-
+  function(new, old, ...) {
+    # If new is element_blank, just return it
+    new
   }
 
-  # actual merging can only happen if classes match
-  if (!inherits(new, class(old)[1])) {
-    cli::cli_abort("Only elements of the same class can be merged.")
-  }
+S7::method(merge_element, list(element, S7::class_any)) <-
+  function(new, old, ...) {
+    if (is.null(old) || is_theme_element(old, "blank")) {
+      # If old is NULL or element_blank, then just return new
+      return(new)
+    }
 
-  # Override NULL properties of new with the values in old
-  # Get logical vector of NULL properties in new
-  idx <- vapply(new, is.null, logical(1))
-  # Get the names of TRUE items
-  idx <- names(idx[idx])
+    # actual merging can only happen if classes match
+    if (!inherits(new, class(old)[1])) {
+      cli::cli_abort("Only elements of the same class can be merged.")
+    }
+
+    # Override NULL properties of new with the values in old
+    # Get logical vector of NULL properties in new
+    idx <- lengths(S7::props(new)) == 0
+    # Get the names of TRUE items
+    idx <- names(idx[idx])
 
-  # Update non-NULL items
-  new[idx] <- old[idx]
+    # Update non-NULL items
+    S7::props(new)[idx] <- S7::props(old, idx)
 
-  new
+    new
 }
 
-#' @rdname merge_element
-#' @export
-merge_element.margin <- function(new, old) {
-  if (is.null(old) || inherits(old, "element_blank")) {
-    return(new)
-  }
-  if (anyNA(new)) {
-    new[is.na(new)] <- old[is.na(new)]
+S7::method(merge_element, list(margin, S7::class_any)) <-
+  function(new, old, ...) {
+    if (is.null(old) || is_theme_element(old, "blank")) {
+      return(new)
+    }
+    if (anyNA(new)) {
+      new[is.na(new)] <- old[is.na(new)]
+    }
+    new
   }
-  new
-}
 
 #' Combine the properties of two elements
 #'
@@ -901,7 +915,7 @@ merge_element.margin <- function(new, old) {
 combine_elements <- function(e1, e2) {
 
   # If e2 is NULL, nothing to inherit
-  if (is.null(e2) || inherits(e1, "element_blank")) {
+  if (is.null(e2) || is_theme_element(e1, "blank")) {
     return(e1)
   }
 
@@ -924,7 +938,7 @@ combine_elements <- function(e1, e2) {
     return(e1)
   }
 
-  if (inherits(e1, "margin") && inherits(e2, "margin")) {
+  if (is_margin(e1) && is_margin(e2)) {
     if (anyNA(e2)) {
       e2[is.na(e2)] <- unit(0, "pt")
     }
@@ -940,8 +954,8 @@ combine_elements <- function(e1, e2) {
 
   # If e2 is element_blank, and e1 inherits blank inherit everything from e2,
   # otherwise ignore e2
-  if (inherits(e2, "element_blank")) {
-    if (e1$inherit.blank) {
+  if (is_theme_element(e2, "blank")) {
+    if (isTRUE(try_prop(e1, "inherit.blank"))) {
       return(e2)
     } else {
       return(e1)
@@ -949,29 +963,29 @@ combine_elements <- function(e1, e2) {
   }
 
   # If e1 has any NULL properties, inherit them from e2
-  n <- names(e1)[vapply(e1, is.null, logical(1))]
-  e1[n] <- e2[n]
+  n <- S7::prop_names(e1)[lengths(S7::props(e1)) == 0]
+  S7::props(e1)[n] <- S7::props(e2)[n]
 
   # Calculate relative sizes
-  if (is.rel(e1$size)) {
-    e1$size <- e2$size * unclass(e1$size)
+  if (is.rel(try_prop(e1, "size"))) {
+    e1@size <- e2@size * unclass(e1@size)
   }
 
   # Calculate relative linewidth
-  if (is.rel(e1$linewidth)) {
-    e1$linewidth <- e2$linewidth * unclass(e1$linewidth)
+  if (is.rel(try_prop(e1, "linewidth"))) {
+    e1@linewidth <- e2@linewidth * unclass(e1@linewidth)
   }
 
-  if (inherits(e1, "element_text")) {
-    e1$margin <- combine_elements(e1$margin, e2$margin)
+  if (is_theme_element(e1, "text")) {
+    e1@margin <- combine_elements(e1@margin, e2@margin)
   }
 
   # If e2 is 'richer' than e1, fill e2 with e1 parameters
   is_subclass <- !any(inherits(e2, class(e1), which = TRUE) == 0)
   is_subclass <- is_subclass && length(setdiff(class(e2), class(e1)) > 0)
   if (is_subclass) {
-    new <- defaults(e1, e2)
-    e2[names(new)] <- new
+    new <- defaults(S7::props(e1), S7::props(e2))
+    S7::props(e2)[names(new)] <- new
     return(e2)
   }
 
diff --git a/R/utilities.R b/R/utilities.R
index 8e6f9d46e9..828c9ab711 100644
--- a/R/utilities.R
+++ b/R/utilities.R
@@ -909,3 +909,13 @@ compute_data_size <- function(data, size, default = 0.9,
   data[[target]] <- res * (default %||% 0.9)
   data
 }
+
+try_prop <- function(object, name, default = NULL) {
+  if (!S7::S7_inherits(object)) {
+    return(default)
+  }
+  if (!S7::prop_exists(object, name)) {
+    return(default)
+  }
+  S7::prop(object, name)
+}
diff --git a/R/zzz.R b/R/zzz.R
index e15bcbd2af..9bfffde0a6 100644
--- a/R/zzz.R
+++ b/R/zzz.R
@@ -30,9 +30,11 @@ on_load(
     vars <- dplyr::vars
   }
 )
+
 on_load(
   if (getRversion() > "4.3.0") registerS3method("+", "gg", add_gg)
 )
+
 on_load(S7::methods_register())
 .onLoad <- function(...) {
   run_on_load()
diff --git a/man/element.Rd b/man/element.Rd
index 84fe10fd20..92046f8267 100644
--- a/man/element.Rd
+++ b/man/element.Rd
@@ -1,6 +1,10 @@
 % Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/theme-elements.R, R/margins.R
-\name{element}
+% Please edit documentation in R/margins.R, R/theme-elements.R
+\name{margin}
+\alias{margin}
+\alias{margin_part}
+\alias{margin_auto}
+\alias{element}
 \alias{element_blank}
 \alias{element_rect}
 \alias{element_line}
@@ -9,11 +13,16 @@
 \alias{element_point}
 \alias{element_geom}
 \alias{rel}
-\alias{margin}
-\alias{margin_part}
-\alias{margin_auto}
 \title{Theme elements}
 \usage{
+margin(t = 0, r = 0, b = 0, l = 0, unit = "pt")
+
+margin_part(t = NA, r = NA, b = NA, l = NA, unit = "pt")
+
+margin_auto(t = 0, r = t, b = t, l = r, unit = "pt")
+
+element()
+
 element_blank()
 
 element_rect(
@@ -22,6 +31,7 @@ element_rect(
   linewidth = NULL,
   linetype = NULL,
   color = NULL,
+  linejoin = NULL,
   inherit.blank = FALSE,
   size = deprecated()
 )
@@ -32,6 +42,7 @@ element_line(
   linetype = NULL,
   lineend = NULL,
   color = NULL,
+  linejoin = NULL,
   arrow = NULL,
   arrow.fill = NULL,
   inherit.blank = FALSE,
@@ -59,6 +70,7 @@ element_polygon(
   linewidth = NULL,
   linetype = NULL,
   color = NULL,
+  linejoin = NULL,
   inherit.blank = FALSE
 )
 
@@ -90,14 +102,13 @@ element_geom(
 )
 
 rel(x)
-
-margin(t = 0, r = 0, b = 0, l = 0, unit = "pt")
-
-margin_part(t = NA, r = NA, b = NA, l = NA, unit = "pt")
-
-margin_auto(t = 0, r = t, b = t, l = r, unit = "pt")
 }
 \arguments{
+\item{t, r, b, l}{Dimensions of each margin. (To remember order, think trouble).}
+
+\item{unit}{Default units of dimensions. Defaults to "pt" so it
+can be most easily scaled with the text.}
+
 \item{fill}{Fill colour. \code{fill_alpha()} can be used to set the transparency
 of the fill.}
 
@@ -111,6 +122,8 @@ integer (0:8), a name (blank, solid, dashed, dotted, dotdash, longdash,
 twodash), or a string with an even number (up to eight) of hexadecimal
 digits which give the lengths in consecutive positions in the string.}
 
+\item{linejoin}{Line join style, one of \code{"round"}, \code{"mitre"} or \code{"bevel"}.}
+
 \item{inherit.blank}{Should this element inherit the existence of an
 \code{element_blank} among its parents? If \code{TRUE} the existence of
 a blank element among its parents will cause this element to be blank as
@@ -119,7 +132,7 @@ calculating final element state.}
 
 \item{size, fontsize, pointsize}{text size in pts, point size in mm.}
 
-\item{lineend}{Line end Line end style (round, butt, square)}
+\item{lineend}{Line end style, one of \code{"round"}, \code{"butt"} or \code{"square"}.}
 
 \item{arrow}{Arrow specification, as created by \code{\link[grid:arrow]{grid::arrow()}}}
 
@@ -154,11 +167,6 @@ is anchored.}
 \item{accent}{Accent colour.}
 
 \item{x}{A single number specifying size relative to parent element.}
-
-\item{t, r, b, l}{Dimensions of each margin. (To remember order, think trouble).}
-
-\item{unit}{Default units of dimensions. Defaults to "pt" so it
-can be most easily scaled with the text.}
 }
 \value{
 An S3 object of class \code{element}, \code{rel}, or \code{margin}.
diff --git a/man/get_theme.Rd b/man/get_theme.Rd
index d3283d0e67..d8198c4197 100644
--- a/man/get_theme.Rd
+++ b/man/get_theme.Rd
@@ -120,5 +120,5 @@ rep_el$text
 
 }
 \seealso{
-\code{\link[=+.gg]{+.gg()}}
+\code{\link[=add_gg]{add_gg()}}
 }
diff --git a/man/ggplot_add.Rd b/man/ggplot_add.Rd
index af044e1748..d1133d26e2 100644
--- a/man/ggplot_add.Rd
+++ b/man/ggplot_add.Rd
@@ -16,7 +16,7 @@ A modified ggplot object
 }
 \description{
 This generic allows you to add your own methods for adding custom objects to
-a ggplot with \link{+.gg}.
+a ggplot with \link[=add_gg]{+.gg}.
 }
 \details{
 Custom methods for \code{ggplot_add()} are intended to update the \code{plot} variable
@@ -29,7 +29,9 @@ exposed at this point, which comes with the responsibility of returning
 the plot intact.
 }
 \examples{
-S7::method(ggplot_add, list(S7::new_S3_class("element_text"), class_ggplot)) <-
+# making a new method for the generic
+# in this example, we enable adding text elements
+S7::method(ggplot_add, list(element_text, class_ggplot)) <-
   function(object, plot, ...) {
     plot + theme(text = object)
   }
@@ -40,6 +42,5 @@ ggplot(mpg, aes(displ, cty)) +
   element_text(colour = "red")
 
 # clean-up
-rm("element_text", envir = ggplot_add@methods)
 }
 \keyword{internal}
diff --git a/man/is_tests.Rd b/man/is_tests.Rd
index bb0b25e799..c3c0630915 100644
--- a/man/is_tests.Rd
+++ b/man/is_tests.Rd
@@ -1,7 +1,7 @@
 % Generated by roxygen2: do not edit by hand
 % Please edit documentation in R/ggproto.R, R/aes.R, R/geom-.R, R/coord-.R,
-%   R/facet-.R, R/stat-.R, R/theme-elements.R, R/guide-.R, R/layer.R,
-%   R/guides-.R, R/margins.R, R/plot.R, R/position-.R, R/scale-.R, R/theme.R
+%   R/facet-.R, R/stat-.R, R/margins.R, R/theme-elements.R, R/guide-.R,
+%   R/layer.R, R/guides-.R, R/plot.R, R/position-.R, R/scale-.R, R/theme.R
 \name{is_ggproto}
 \alias{is_ggproto}
 \alias{is.ggproto}
@@ -12,11 +12,11 @@
 \alias{is_facet}
 \alias{is.facet}
 \alias{is_stat}
+\alias{is_margin}
 \alias{is_theme_element}
 \alias{is_guide}
 \alias{is_layer}
 \alias{is_guides}
-\alias{is_margin}
 \alias{is_tests}
 \alias{is_ggplot}
 \alias{is.ggplot}
@@ -44,6 +44,8 @@ is.facet(x) # Deprecated
 
 is_stat(x)
 
+is_margin(x)
+
 is_theme_element(x, type = "any")
 
 is_guide(x)
@@ -52,8 +54,6 @@ is_layer(x)
 
 is_guides(x)
 
-is_margin(x)
-
 is_ggplot(x)
 
 is.ggplot(x) # Deprecated
@@ -70,7 +70,7 @@ is.theme(x) # Deprecated
 \item{x}{An object to test}
 
 \item{type}{For testing elements: the type of element to expect. One of
-\code{"blank"}, \code{"rect"}, \code{"line"} or \code{"text"}.}
+\code{"blank"}, \code{"rect"}, \code{"line"}, \code{"text"}, \code{"polygon"}, \code{"point"} or \code{"geom"}.}
 }
 \description{
 Reports wether \code{x} is a type of object
diff --git a/man/merge_element.Rd b/man/merge_element.Rd
index ca993eeec3..3060360dc0 100644
--- a/man/merge_element.Rd
+++ b/man/merge_element.Rd
@@ -2,21 +2,9 @@
 % Please edit documentation in R/theme.R
 \name{merge_element}
 \alias{merge_element}
-\alias{merge_element.default}
-\alias{merge_element.element_blank}
-\alias{merge_element.element}
-\alias{merge_element.margin}
 \title{Merge a parent element into a child element}
 \usage{
-merge_element(new, old)
-
-\method{merge_element}{default}(new, old)
-
-\method{merge_element}{element_blank}(new, old)
-
-\method{merge_element}{element}(new, old)
-
-\method{merge_element}{margin}(new, old)
+merge_element(new, old, ...)
 }
 \arguments{
 \item{new}{The child element in the theme hierarchy}
diff --git a/man/register_theme_elements.Rd b/man/register_theme_elements.Rd
index cdbbb25d70..0cb822e686 100644
--- a/man/register_theme_elements.Rd
+++ b/man/register_theme_elements.Rd
@@ -27,8 +27,8 @@ a list of named element definitions created with el_def().}
 \item{reset_current}{If \code{TRUE} (the default), the currently active theme is
 reset to the default theme.}
 
-\item{class}{The name of the element class. Examples are "element_line" or
-"element_text" or "unit", or one of the two reserved keywords "character" or
+\item{class}{The name of the element class. Examples are \code{element_line} or
+\code{element_text} or "unit", or one of the two reserved keywords "character" or
 "margin". The reserved keyword "character" implies a character
 or numeric vector, not a class called "character". The keyword
 "margin" implies a unit vector of length 4, as created by \code{\link[=margin]{margin()}}.}
@@ -76,7 +76,7 @@ element inheritance relationships for the element tree.
 # plot panels. To do so, it registers a new theme element `ggxyz.panel.annotation`
 register_theme_elements(
   ggxyz.panel.annotation = element_text(color = "blue", hjust = 0.95, vjust = 0.05),
-  element_tree = list(ggxyz.panel.annotation = el_def("element_text", "text"))
+  element_tree = list(ggxyz.panel.annotation = el_def(element_text, "text"))
 )
 
 # Now the package can define a new coord that includes a panel annotation
diff --git a/man/theme.Rd b/man/theme.Rd
index 2766a3f8ca..f2a9bdf33f 100644
--- a/man/theme.Rd
+++ b/man/theme.Rd
@@ -519,7 +519,7 @@ p3 + theme(panel.spacing = unit(1, "lines"))
 }
 }
 \seealso{
-\code{\link[=+.gg]{+.gg()}} and \link{\%+replace\%},
+\code{\link[=add_gg]{add_gg()}} and \link{\%+replace\%},
 \code{\link[=element_blank]{element_blank()}}, \code{\link[=element_line]{element_line()}},
 \code{\link[=element_rect]{element_rect()}}, and \code{\link[=element_text]{element_text()}} for
 details of the specific theme elements.
diff --git a/tests/testthat/_snaps/theme.md b/tests/testthat/_snaps/theme.md
index 3694f73097..bd92d95024 100644
--- a/tests/testthat/_snaps/theme.md
+++ b/tests/testthat/_snaps/theme.md
@@ -9,7 +9,7 @@
 # incorrect theme specifications throw meaningful errors
 
     Can't merge the `line` theme element.
-    Caused by error in `merge_element()`:
+    Caused by error in `method(merge_element, list(ggplot2::element, class_any))`:
     ! Only elements of the same class can be merged.
 
 ---
@@ -18,7 +18,7 @@
 
 ---
 
-    Theme element `test` has `NULL` property without default: fill, colour, linewidth, and linetype.
+    Theme element `test` has `NULL` property without default: fill, colour, linewidth, linetype, and linejoin.
 
 ---
 
@@ -58,7 +58,7 @@
     Code
       merge_element(text_base, rect_base)
     Condition
-      Error in `merge_element()`:
+      Error in `method(merge_element, list(ggplot2::element, class_any))`:
       ! Only elements of the same class can be merged.
 
 # Theme elements are checked during build
diff --git a/tests/testthat/test-theme.R b/tests/testthat/test-theme.R
index 7267fb48dc..5872e9f14a 100644
--- a/tests/testthat/test-theme.R
+++ b/tests/testthat/test-theme.R
@@ -21,8 +21,8 @@ test_that("modifying theme element properties with + operator works", {
   # Make sure the theme class didn't change or get dropped
   expect_s7_class(t, class_theme)
   # Make sure the element class didn't change or get dropped
-  expect_s3_class(t$axis.title.x, "element")
-  expect_s3_class(t$axis.title.x, "element_text")
+  expect_s7_class(t$axis.title.x, element)
+  expect_s7_class(t$axis.title.x, element_text)
 
   # Modifying an intermediate node works
   t <- theme_grey() + theme(axis.title = element_text(colour = 'red'))
@@ -30,10 +30,10 @@ test_that("modifying theme element properties with + operator works", {
 
   # Modifying a root node changes only the specified properties
   t <- theme_grey() + theme(text = element_text(colour = 'red'))
-  expect_identical(t$text$colour, 'red')
-  expect_identical(t$text$family, theme_grey()$text$family)
-  expect_identical(t$text$face,   theme_grey()$text$face)
-  expect_identical(t$text$size,   theme_grey()$text$size)
+  expect_identical(t$text@colour, 'red')
+  expect_identical(t$text@family, theme_grey()$text@family)
+  expect_identical(t$text@face,   theme_grey()$text@face)
+  expect_identical(t$text@size,   theme_grey()$text@size)
   # Descendent is unchanged
   expect_identical(t$axis.title.x, theme_grey()$axis.title.x)
 
@@ -60,34 +60,34 @@ test_that("adding theme object to ggplot object with + operator works", {
   ## test with complete theme
   p <- ggplot(data.frame(x = 1:3), aes(x, x)) + geom_point() + theme_grey()
   p <- p + theme(axis.title = element_text(size = 20))
-  expect_true(p@theme$axis.title$size == 20)
+  expect_true(p@theme$axis.title@size == 20)
 
   # Should update specified properties, but not reset other properties
   p <- p + theme(text = element_text(colour = 'red'))
-  expect_true(p@theme$text$colour == 'red')
+  expect_true(p@theme$text@colour == 'red')
   tt <- theme_grey()$text
-  tt$colour <- 'red'
-  expect_true(tt$inherit.blank)
-  tt$inherit.blank <- FALSE
+  tt@colour <- 'red'
+  expect_true(tt@inherit.blank)
+  tt@inherit.blank <- FALSE
   expect_identical(p@theme$text, tt)
 
   ## test without complete theme
   p <- ggplot(data.frame(x = 1:3), aes(x, x)) + geom_point()
   p <- p + theme(axis.title = element_text(size = 20))
-  expect_true(p@theme$axis.title$size == 20)
+  expect_true(p@theme$axis.title@size == 20)
 
   # Should update specified properties, but not reset other properties
   p <- p + theme(text = element_text(colour = 'red'))
-  expect_true(p@theme$text$colour == 'red')
-  expect_null(p@theme$text$family)
-  expect_null(p@theme$text$face)
-  expect_null(p@theme$text$size)
-  expect_null(p@theme$text$hjust)
-  expect_null(p@theme$text$vjust)
-  expect_null(p@theme$text$angle)
-  expect_null(p@theme$text$lineheight)
-  expect_null(p@theme$text$margin)
-  expect_null(p@theme$text$debug)
+  expect_true(p@theme$text@colour == 'red')
+  expect_null(p@theme$text@family)
+  expect_null(p@theme$text@face)
+  expect_null(p@theme$text@size)
+  expect_null(p@theme$text@hjust)
+  expect_null(p@theme$text@vjust)
+  expect_null(p@theme$text@angle)
+  expect_null(p@theme$text@lineheight)
+  expect_null(p@theme$text@margin)
+  expect_null(p@theme$text@debug)
 
   ## stepwise addition of partial themes is identical to one-step addition
   p <- ggplot(data.frame(x = 1:3), aes(x, x)) + geom_point()
@@ -125,36 +125,34 @@ test_that("calculating theme element inheritance works", {
 
   # Check that properties are passed along from axis.title to axis.title.x
   e <- calc_element('axis.title.x', t)
-  expect_identical(e$colour, 'red')
-  expect_false(is.null(e$family))
-  expect_false(is.null(e$face))
-  expect_false(is.null(e$size))
+  expect_identical(e@colour, 'red')
+  expect_false(is.null(e@family))
+  expect_false(is.null(e@face))
+  expect_false(is.null(e@size))
 
   # Check that rel() works for relative sizing, and is applied at each level
   t <- theme_grey(base_size = 12) +
     theme(axis.title   = element_text(size = rel(0.5))) +
     theme(axis.title.x = element_text(size = rel(0.5)))
   e <- calc_element('axis.title', t)
-  expect_identical(e$size, 6)
+  expect_identical(e@size, 6)
   ex <- calc_element('axis.title.x', t)
-  expect_identical(ex$size, 3)
+  expect_identical(ex@size, 3)
 
   # Check that a theme_blank in a parent node gets passed along to children
   t <- theme_grey() + theme(text = element_blank())
   expect_identical(calc_element('axis.title.x', t), element_blank())
 
   # Check that inheritance from derived class works
-  element_dummyrect <- function(dummy) { # like element_rect but w/ dummy argument
-    structure(list(
-      fill = NULL, colour = NULL, dummy = dummy, linewidth = NULL,
-      linetype = NULL, inherit.blank = FALSE
-    ), class = c("element_dummyrect", "element_rect", "element"))
-  }
+  element_dummyrect <- S7::new_class(
+    "element_dummyrect", parent = element_rect,
+    properties = c(element_rect@properties, list(dummy = S7::class_any))
+  )
 
   e <- calc_element(
     "panel.background",
     theme(
-      rect = element_rect(fill = "white", colour = "black", linewidth = 0.5, linetype = 1),
+      rect = element_rect(fill = "white", colour = "black", linewidth = 0.5, linetype = 1, linejoin = "round"),
       panel.background = element_dummyrect(dummy = 5),
       complete = TRUE # need to prevent pulling in default theme
     )
@@ -162,10 +160,10 @@ test_that("calculating theme element inheritance works", {
 
   expect_identical(
     e,
-    structure(list(
-      fill = "white", colour = "black", dummy = 5, linewidth = 0.5, linetype = 1,
+    element_dummyrect(
+      fill = "white", colour = "black", dummy = 5, linewidth = 0.5, linetype = 1, linejoin = "round",
       inherit.blank = TRUE # this is true because we're requesting a complete theme
-    ), class = c("element_dummyrect", "element_rect", "element"))
+    )
   )
 
   # Check that blank elements are skipped in inheritance tree if and only if elements
@@ -177,7 +175,7 @@ test_that("calculating theme element inheritance works", {
     )
   e1 <- calc_element("strip.text.x", t)
   e2 <- calc_element("text", t)
-  e2$inherit.blank <- FALSE # b/c inherit.blank = TRUE for complete themes
+  e2@inherit.blank <- FALSE # b/c inherit.blank = TRUE for complete themes
   expect_identical(e1, e2)
 
   theme <- theme_gray() +
@@ -203,18 +201,18 @@ test_that("complete and non-complete themes interact correctly with each other",
   # But for _element properties_, the one on the right modifies the one on the left.
   t <- theme_bw() + theme(text = element_text(colour = 'red'))
   expect_true(attr(t, "complete"))
-  expect_equal(t$text$colour, 'red')
+  expect_equal(t$text@colour, 'red')
 
   # A complete theme object (like theme_bw) always trumps a non-complete theme object
   t <- theme(text = element_text(colour = 'red')) + theme_bw()
   expect_true(attr(t, "complete"))
-  expect_equal(t$text$colour, theme_bw()$text$colour)
+  expect_equal(t$text@colour, theme_bw()$text@colour)
 
   # Adding two non-complete themes: the one on the right modifies the one on the left.
   t <- theme(text = element_text(colour = 'blue')) +
     theme(text = element_text(colour = 'red'))
   expect_false(attr(t, "complete"))
-  expect_equal(t$text$colour, 'red')
+  expect_equal(t$text@colour, 'red')
 })
 
 test_that("complete and non-complete themes interact correctly with ggplot objects", {
@@ -242,14 +240,14 @@ test_that("complete and non-complete themes interact correctly with ggplot objec
   expect_identical(pt, tt)
 
   p <- ggplot_build(base + theme(text = element_text(colour = 'red', face = 'italic')))
-  expect_equal(p@plot@theme$text$colour, "red")
-  expect_equal(p@plot@theme$text$face, "italic")
+  expect_equal(p@plot@theme$text@colour, "red")
+  expect_equal(p@plot@theme$text@face, "italic")
 
   p <- ggplot_build(base +
     theme(text = element_text(colour = 'red')) +
     theme(text = element_text(face = 'italic')))
-  expect_equal(p@plot@theme$text$colour, "red")
-  expect_equal(p@plot@theme$text$face, "italic")
+  expect_equal(p@plot@theme$text@colour, "red")
+  expect_equal(p@plot@theme$text@face, "italic")
 })
 
 test_that("theme(validate=FALSE) means do not check_element", {
@@ -285,9 +283,10 @@ test_that("theme validation happens at build stage", {
 test_that("incorrect theme specifications throw meaningful errors", {
   expect_snapshot_error(add_theme(theme_grey(), theme(line = element_rect())))
   expect_snapshot_error(calc_element("line", theme(line = element_rect())))
-  register_theme_elements(element_tree = list(test = el_def("element_rect")))
+  register_theme_elements(element_tree = list(test = el_def(element_rect)))
   expect_snapshot_error(calc_element("test", theme_gray() + theme(test = element_rect())))
   expect_snapshot_error(set_theme("foo"))
+  reset_theme_settings()
 })
 
 test_that("element tree can be modified", {
@@ -307,7 +306,7 @@ test_that("element tree can be modified", {
 
   # things work once we add a new element to the element tree
   register_theme_elements(
-    element_tree = list(blablabla = el_def("element_text", "text"))
+    element_tree = list(blablabla = el_def(element_text, "text"))
   )
   expect_silent(ggplotGrob(p))
 
@@ -329,31 +328,29 @@ test_that("element tree can be modified", {
   final_theme <- ggplot2:::plot_theme(p, theme_gray())
   e1 <- calc_element("blablabla", final_theme)
   e2 <- calc_element("text", final_theme)
-  expect_identical(e1$family, e2$family)
-  expect_identical(e1$face, e2$face)
-  expect_identical(e1$size, e2$size)
-  expect_identical(e1$lineheight, e2$lineheight)
-  expect_identical(e1$colour, "red") # not inherited from element_text
+  expect_identical(e1@family, e2@family)
+  expect_identical(e1@face, e2@face)
+  expect_identical(e1@size, e2@size)
+  expect_identical(e1@lineheight, e2@lineheight)
+  expect_identical(e1@colour, "red") # not inherited from element_text
 
   # existing elements can be overwritten
-  ed <- el_def("element_rect", "rect")
+  ed <- el_def(element_rect, "rect")
   register_theme_elements(
     element_tree = list(axis.title = ed)
   )
   expect_identical(get_element_tree()$axis.title, ed)
 
-  reset_theme_settings(reset_current = FALSE) # revert back to defaults
+  reset_theme_settings() # revert back to defaults
 })
 
 test_that("all elements in complete themes have inherit.blank=TRUE", {
   inherit_blanks <- function(theme) {
-    all(vapply(theme, function(el) {
-      if (is_theme_element(el) && !is_theme_element(el, "blank")) {
-        el$inherit.blank
-      } else {
-        TRUE
-      }
-    }, logical(1)))
+    all(vapply(
+      theme, try_prop,
+      name = "inherit.blank", default = TRUE,
+      logical(1)
+    ))
   }
   expect_true(inherit_blanks(theme_grey()))
   expect_true(inherit_blanks(theme_bw()))
@@ -395,7 +392,7 @@ test_that("complete plot themes shouldn't inherit from default", {
   base <- ggplot(data.frame(x = 1), aes(x, x)) + geom_point()
 
   ptheme <- plot_theme(base + theme(axis.text.x = element_text(colour = "blue")), default_theme)
-  expect_equal(ptheme$axis.text.x$colour, "blue")
+  expect_equal(ptheme$axis.text.x@colour, "blue")
 
   ptheme <- plot_theme(base + theme_void(), default_theme)
   expect_null(ptheme$axis.text.x)
@@ -425,14 +422,14 @@ test_that("current theme can be updated with new elements", {
   # element tree gets merged properly
   register_theme_elements(
     abcde = element_text(color = "blue", hjust = 0, vjust = 1),
-    element_tree = list(abcde = el_def("element_text", "text"))
+    element_tree = list(abcde = el_def(element_text, "text"))
   )
 
   e1 <- calc_element("abcde", plot_theme(b2))
   e2 <- calc_element("text", plot_theme(b2))
-  e2$colour <- "blue"
-  e2$hjust <- 0
-  e2$vjust <- 1
+  e2@colour <- "blue"
+  e2@hjust <- 0
+  e2@vjust <- 1
   expect_identical(e1, e2)
 
   reset_theme_settings()
@@ -567,7 +564,7 @@ test_that("Element subclasses are inherited", {
   test <- combine_elements(poor, rich)
   expect_s3_class(test, "element_rich")
   expect_equal(
-    test[c("colour", "linetype", "linewidth")],
+    S7::props(test)[c("colour", "linetype", "linewidth")],
     list(colour = "red", linetype = 3, linewidth = 2)
   )
 
@@ -575,7 +572,7 @@ test_that("Element subclasses are inherited", {
   test <- combine_elements(rich, poor)
   expect_s3_class(test, "element_rich")
   expect_equal(
-    test[c("colour", "linetype", "linewidth")],
+    S7::props(test)[c("colour", "linetype", "linewidth")],
     list(colour = "red", linetype = 2, linewidth = 2)
   )
 
@@ -587,7 +584,7 @@ test_that("Element subclasses are inherited", {
   test <- combine_elements(sibling, rich)
   expect_s3_class(test, "element_sibling")
   expect_equal(
-    test[c("colour", "linetype", "linewidth")],
+    S7::props(test)[c("colour", "linetype", "linewidth")],
     list(colour = "red", linetype = 3, linewidth = 2)
   )
 
@@ -595,7 +592,7 @@ test_that("Element subclasses are inherited", {
   test <- combine_elements(rich, sibling)
   expect_s3_class(test, "element_rich")
   expect_equal(
-    test[c("colour", "linetype", "linewidth")],
+    S7::props(test)[c("colour", "linetype", "linewidth")],
     list(colour = "red", linetype = 2, linewidth = 2)
   )
 })
@@ -622,10 +619,10 @@ test_that("header_family is passed on correctly", {
   td <- theme_dark(base_family = "x", header_family = "y")
 
   test <- calc_element("plot.title", td)
-  expect_equal(test$family, "y")
+  expect_equal(test@family, "y")
 
   test <- calc_element("plot.subtitle", td)
-  expect_equal(test$family, "x")
+  expect_equal(test@family, "x")
 })
 
 test_that("complete_theme completes a theme", {
@@ -636,19 +633,19 @@ test_that("complete_theme completes a theme", {
 
   # Elements are propagated
   new <- complete_theme(theme(axis.line = element_line("red")), gray)
-  expect_equal(new$axis.line$colour, "red")
+  expect_equal(new$axis.line@colour, "red")
 
   # Missing elements are filled in if default theme is incomplete
   new <- complete_theme(default = theme())
-  expect_s3_class(new$axis.line, "element_blank")
+  expect_s3_class(new$axis.line, "ggplot2::element_blank")
 
   # Registered elements are included
   register_theme_elements(
     test = element_text(),
-    element_tree = list(test = el_def("element_text", "text"))
+    element_tree = list(test = el_def(element_text, "text"))
   )
   new <- complete_theme(default = gray)
-  expect_s3_class(new$test, "element_text")
+  expect_s3_class(new$test, "ggplot2::element_text")
   reset_theme_settings()
 })
 
@@ -985,15 +982,11 @@ test_that("Legends can on all sides of the plot with custom justification", {
 })
 
 test_that("Strips can render custom elements", {
-  element_test <- function(...) {
-    el <- element_text(...)
-    class(el) <- c("element_test", "element_text", "element")
-    el
-  }
-  element_grob.element_test <- function(element, label = "", x = NULL, y = NULL, ...) {
-    rectGrob(width = unit(1, "cm"), height = unit(1, "cm"))
-  }
-  registerS3method("element_grob", "element_test", element_grob.element_test)
+  element_test <- S7::new_class("element_test", element_text)
+  S7::method(element_grob, element_test) <-
+    function(element, label = "", x = NULL, y = NULL, ...) {
+      rectGrob(width = unit(1, "cm"), height = unit(1, "cm"))
+    }
 
   df <- data_frame(x = 1:3, y = 1:3, a = letters[1:3])
   plot <- ggplot(df, aes(x, y)) +
diff --git a/vignettes/articles/faq-axes.Rmd b/vignettes/articles/faq-axes.Rmd
index cf88240cfa..1f08b48dce 100644
--- a/vignettes/articles/faq-axes.Rmd
+++ b/vignettes/articles/faq-axes.Rmd
@@ -444,6 +444,8 @@ ggplot(mpg, aes(x = cty^2, y = log(hwy, base = 10))) +
   )
 ```
 
+<!-- Temporarily disabled while migrating to S7
+
 -   If you're already familiar with Markdown and HTML, you might prefer using the [ggtext](https://wilkelab.org/ggtext/) package instead. In Markdown we can write the axis labels as `cty<sup>2</sup>` and `log<sub>10</sub>(hwy)` for x and y axes, respectively. Then, we tell ggplot2 to interpret the axis labels as Markdown and not as plain text by setting `axis.title.x` and `axis.title.y` to `ggtext::element_markdown()`.
 
 ```{r}
@@ -463,6 +465,7 @@ ggplot(mpg, aes(x = cty^2, y = log(hwy, base = 10))) +
     axis.title.y = ggtext::element_markdown()
     )
 ```
+-->
 
 </details>