diff --git a/R/coord-radial.R b/R/coord-radial.R
index 1b4da20a23..ba0146954f 100644
--- a/R/coord-radial.R
+++ b/R/coord-radial.R
@@ -191,7 +191,7 @@ CoordRadial <- ggproto("CoordRadial", Coord,
     # Validate appropriateness of guides
     drop_guides <- character(0)
     for (type in aesthetics) {
-      drop_guides <- check_polar_guide(drop_guides, guides, type)
+      drop_guides <- validate_polar_guide(drop_guides, guides, type)
     }
 
     guide_params <- guides$get_params(aesthetics)
@@ -603,7 +603,7 @@ theta_grid <- function(theta, element, inner_radius = c(0, 0.4),
   )
 }
 
-check_polar_guide <- function(drop_list, guides, type = "theta") {
+validate_polar_guide <- function(drop_list, guides, type = "theta") {
   guide <- guides$get_guide(type)
   primary <- gsub("\\.sec$", "", type)
   if (inherits(guide, "GuideNone") || primary %in% guide$available_aes) {
diff --git a/R/facet-.R b/R/facet-.R
index b124b54872..0c120beba3 100644
--- a/R/facet-.R
+++ b/R/facet-.R
@@ -443,7 +443,7 @@ df.grid <- function(a, b) {
 # facetting variables.
 
 as_facets_list <- function(x) {
-  x <- validate_facets(x)
+  check_vars(x)
   if (is_quosures(x)) {
     x <- quos_auto_name(x)
     return(list(x))
@@ -487,7 +487,7 @@ as_facets_list <- function(x) {
   x
 }
 
-validate_facets <- function(x) {
+check_vars <- function(x) {
   if (is.mapping(x)) {
     cli::cli_abort("Please use {.fn vars} to supply facet variables.")
   }
@@ -499,7 +499,7 @@ validate_facets <- function(x) {
       "i" = "Did you use {.code %>%} or {.code |>} instead of {.code +}?"
     ))
   }
-  x
+  invisible()
 }
 
 # Flatten a list of quosures objects to a quosures object, and compact it
diff --git a/R/facet-grid-.R b/R/facet-grid-.R
index 784e394885..be11524541 100644
--- a/R/facet-grid-.R
+++ b/R/facet-grid-.R
@@ -177,7 +177,7 @@ facet_grid <- function(rows = NULL, cols = NULL, scales = "fixed",
   facets_list <- grid_as_facets_list(rows, cols)
 
   # Check for deprecated labellers
-  labeller <- check_labeller(labeller)
+  labeller <- fix_labeller(labeller)
 
   ggproto(NULL, FacetGrid,
     shrink = shrink,
diff --git a/R/facet-wrap.R b/R/facet-wrap.R
index 114b3332d9..6bc72f8af4 100644
--- a/R/facet-wrap.R
+++ b/R/facet-wrap.R
@@ -174,7 +174,7 @@ facet_wrap <- function(facets, nrow = NULL, ncol = NULL, scales = "fixed",
   )
 
   # Check for deprecated labellers
-  labeller <- check_labeller(labeller)
+  labeller <- fix_labeller(labeller)
 
   # Flatten all facets dimensions into a single one
   facets <- compact_facets(facets)
diff --git a/R/fortify.R b/R/fortify.R
index da4bcf7892..17d6e37b12 100644
--- a/R/fortify.R
+++ b/R/fortify.R
@@ -44,34 +44,46 @@ fortify.grouped_df <- function(model, data, ...) {
 # There are a lot of ways that dim(), colnames(), or as.data.frame() could
 # do non-sensical things (they are not even guaranteed to work!) hence the
 # paranoid mode.
-.prevalidate_data_frame_like_object <- function(data) {
+check_data_frame_like <- function(data) {
   orig_dims <- dim(data)
-  if (!vec_is(orig_dims, integer(), size=2))
-    cli::cli_abort(paste0("{.code dim(data)} must return ",
-                          "an {.cls integer} of length 2."))
-  if (anyNA(orig_dims) || any(orig_dims < 0))  # extra-paranoid mode
-    cli::cli_abort(paste0("{.code dim(data)} can't have {.code NA}s ",
-                          "or negative values."))
+  if (!vec_is(orig_dims, integer(), size = 2)) {
+    cli::cli_abort(
+      "{.code dim(data)} must return an {.cls integer} of length 2."
+    )
+  }
+  if (anyNA(orig_dims) || any(orig_dims < 0)) { # extra-paranoid mode
+    cli::cli_abort(
+      "{.code dim(data)} can't have {.code NA}s or negative values."
+    )
+  }
   orig_colnames <- colnames(data)
-  if (!vec_is(orig_colnames, character(), size = ncol(data)))
-    cli::cli_abort(paste0("{.code colnames(data)} must return a ",
-                          "{.cls character} of length {.code ncol(data)}."))
+  if (!vec_is(orig_colnames, character(), size = ncol(data))) {
+    cli::cli_abort(
+      "{.code colnames(data)} must return a {.cls character} of length {.code ncol(data)}."
+    )
+  }
+  invisible()
 }
-.postvalidate_data_frame_like_object <- function(df, data) {
+check_data_frame_conversion <- function(new, old) {
   msg0 <- "{.code as.data.frame(data)} must "
-  if (!is.data.frame(df))
+  if (!is.data.frame(new)) {
     cli::cli_abort(paste0(msg0, "return a {.cls data.frame}."))
-  if (!identical(dim(df), dim(data)))
+  }
+  if (!identical(dim(new), dim(old))) {
     cli::cli_abort(paste0(msg0, "preserve dimensions."))
-  if (!identical(colnames(df), colnames(data)))
+  }
+  if (!identical(colnames(new), colnames(old))) {
     cli::cli_abort(paste0(msg0, "preserve column names."))
+  }
+  invisible()
 }
 validate_as_data_frame <- function(data) {
-  if (is.data.frame(data))
+  if (is.data.frame(data)) {
     return(data)
-  .prevalidate_data_frame_like_object(data)
+  }
+  check_data_frame_like(data)
   df <- as.data.frame(data)
-  .postvalidate_data_frame_like_object(df, data)
+  check_data_frame_conversion(df, data)
   df
 }
 
diff --git a/R/geom-.R b/R/geom-.R
index 50bdeb66a6..f8b5027438 100644
--- a/R/geom-.R
+++ b/R/geom-.R
@@ -170,17 +170,11 @@ Geom <- ggproto("Geom",
       )
 
       # Check that all output are valid data
-      nondata_modified <- check_nondata_cols(modified_aes)
-      if (length(nondata_modified) > 0) {
-        issues <- paste0("{.code ", nondata_modified, " = ", as_label(modifiers[[nondata_modified]]), "}")
-        names(issues) <- rep("x", length(issues))
-        cli::cli_abort(c(
-          "Aesthetic modifiers returned invalid values",
-          "x" = "The following mappings are invalid",
-          issues,
-          "i" = "Did you map the modifier in the wrong layer?"
-        ))
-      }
+      check_nondata_cols(
+        modified_aes, modifiers,
+        problem = "Aesthetic modifiers returned invalid values.",
+        hint    = "Did you map the modifier in the wrong layer?"
+      )
 
       modified_aes <- cleanup_mismatched_data(modified_aes, nrow(data), "after_scale")
 
@@ -283,7 +277,7 @@ check_aesthetics <- function(x, n) {
   ))
 }
 
-check_linewidth <- function(data, name) {
+fix_linewidth <- function(data, name) {
   if (is.null(data$linewidth) && !is.null(data$size)) {
     deprecate_soft0("3.4.0", I(paste0("Using the `size` aesthetic with ", name)), I("the `linewidth` aesthetic"))
     data$linewidth <- data$size
diff --git a/R/geom-boxplot.R b/R/geom-boxplot.R
index efb6dd14bd..76b09900e1 100644
--- a/R/geom-boxplot.R
+++ b/R/geom-boxplot.R
@@ -286,7 +286,7 @@ GeomBoxplot <- ggproto("GeomBoxplot", Geom,
                         whisker_gp = NULL, staple_gp = NULL, median_gp = NULL,
                         box_gp = NULL, notch = FALSE, notchwidth = 0.5,
                         staplewidth = 0, varwidth = FALSE, flipped_aes = FALSE) {
-    data <- check_linewidth(data, snake_class(self))
+    data <- fix_linewidth(data, snake_class(self))
     data <- flip_data(data, flipped_aes)
     # this may occur when using geom_boxplot(stat = "identity")
     if (nrow(data) != 1) {
diff --git a/R/geom-crossbar.R b/R/geom-crossbar.R
index be7ce1f658..7316033de6 100644
--- a/R/geom-crossbar.R
+++ b/R/geom-crossbar.R
@@ -84,8 +84,7 @@ GeomCrossbar <- ggproto("GeomCrossbar", Geom,
   draw_panel = function(self, data, panel_params, coord, lineend = "butt",
                         linejoin = "mitre", fatten = 2.5, width = NULL,
                         flipped_aes = FALSE, middle_gp = NULL, box_gp = NULL) {
-
-    data <- check_linewidth(data, snake_class(self))
+    data <- fix_linewidth(data, snake_class(self))
     data <- flip_data(data, flipped_aes)
 
     middle <- transform(data, x = xmin, xend = xmax, yend = y, linewidth = linewidth * fatten, alpha = NA)
diff --git a/R/geom-defaults.R b/R/geom-defaults.R
index 732f5ddb32..c1bc8a782f 100644
--- a/R/geom-defaults.R
+++ b/R/geom-defaults.R
@@ -106,7 +106,7 @@ get_geom_defaults <- function(geom, theme = theme_get()) {
     return(data)
   }
   if (is.character(geom)) {
-    geom <- check_subclass(geom, "Geom")
+    geom <- validate_subclass(geom, "Geom")
   }
   if (is.geom(geom)) {
     out <- geom$use_defaults(data = NULL, theme = theme)
@@ -126,7 +126,7 @@ reset_stat_defaults <- function() reset_defaults("stat")
 cache_defaults <- new_environment()
 
 update_defaults <- function(name, subclass, new, env = parent.frame()) {
-  obj   <- check_subclass(name, subclass, env = env)
+  obj   <- validate_subclass(name, subclass, env = env)
   index <- snake_class(obj)
 
   if (is.null(new)) { # Reset from cache
diff --git a/R/geom-errorbar.R b/R/geom-errorbar.R
index 7551f0be59..cd87edc652 100644
--- a/R/geom-errorbar.R
+++ b/R/geom-errorbar.R
@@ -89,7 +89,7 @@ GeomErrorbar <- ggproto("GeomErrorbar", Geom,
 
   draw_panel = function(self, data, panel_params, coord, lineend = "butt",
                         width = NULL, flipped_aes = FALSE) {
-    data <- check_linewidth(data, snake_class(self))
+    data <- fix_linewidth(data, snake_class(self))
     data <- flip_data(data, flipped_aes)
     x <- vec_interleave(data$xmin, data$xmax, NA, data$x,    data$x,    NA, data$xmin, data$xmax)
     y <- vec_interleave(data$ymax, data$ymax, NA, data$ymax, data$ymin, NA, data$ymin, data$ymin)
diff --git a/R/geom-hex.R b/R/geom-hex.R
index 152227a40b..5add9250c8 100644
--- a/R/geom-hex.R
+++ b/R/geom-hex.R
@@ -58,7 +58,7 @@ geom_hex <- function(mapping = NULL, data = NULL,
 GeomHex <- ggproto("GeomHex", Geom,
   draw_group = function(self, data, panel_params, coord, lineend = "butt",
                         linejoin = "mitre", linemitre = 10) {
-    data <- check_linewidth(data, snake_class(self))
+    data <- fix_linewidth(data, snake_class(self))
     if (empty(data)) {
       return(zeroGrob())
     }
diff --git a/R/geom-path.R b/R/geom-path.R
index 72c4f7154e..fe930363a6 100644
--- a/R/geom-path.R
+++ b/R/geom-path.R
@@ -165,7 +165,7 @@ GeomPath <- ggproto("GeomPath", Geom,
   draw_panel = function(self, data, panel_params, coord, arrow = NULL, arrow.fill = NULL,
                         lineend = "butt", linejoin = "round", linemitre = 10,
                         na.rm = FALSE) {
-    data <- check_linewidth(data, snake_class(self))
+    data <- fix_linewidth(data, snake_class(self))
     if (!anyDuplicated(data$group)) {
       cli::cli_inform(c(
         "{.fn {snake_class(self)}}: Each group consists of only one observation.",
diff --git a/R/geom-polygon.R b/R/geom-polygon.R
index a271ef5011..a97d3c2194 100644
--- a/R/geom-polygon.R
+++ b/R/geom-polygon.R
@@ -109,7 +109,7 @@ geom_polygon <- function(mapping = NULL, data = NULL,
 GeomPolygon <- ggproto("GeomPolygon", Geom,
   draw_panel = function(self, data, panel_params, coord, rule = "evenodd",
                         lineend = "butt", linejoin = "round", linemitre = 10) {
-    data <- check_linewidth(data, snake_class(self))
+    data <- fix_linewidth(data, snake_class(self))
     n <- nrow(data)
     if (n == 1) return(zeroGrob())
 
diff --git a/R/geom-rect.R b/R/geom-rect.R
index 8473474525..1765a2506a 100644
--- a/R/geom-rect.R
+++ b/R/geom-rect.R
@@ -69,7 +69,7 @@ GeomRect <- ggproto("GeomRect", Geom,
   },
 
   draw_panel = function(self, data, panel_params, coord, lineend = "butt", linejoin = "mitre") {
-    data <- check_linewidth(data, snake_class(self))
+    data <- fix_linewidth(data, snake_class(self))
     if (!coord$is_linear()) {
       aesthetics <- setdiff(
         names(data), c("x", "y", "xmin", "xmax", "ymin", "ymax")
diff --git a/R/geom-ribbon.R b/R/geom-ribbon.R
index a8f6b1be42..ee5a43b20e 100644
--- a/R/geom-ribbon.R
+++ b/R/geom-ribbon.R
@@ -133,7 +133,7 @@ GeomRibbon <- ggproto("GeomRibbon", Geom,
   draw_group = function(self, data, panel_params, coord, lineend = "butt",
                         linejoin = "round", linemitre = 10, na.rm = FALSE,
                         flipped_aes = FALSE, outline.type = "both") {
-    data <- check_linewidth(data, snake_class(self))
+    data <- fix_linewidth(data, snake_class(self))
     data <- flip_data(data, flipped_aes)
     if (na.rm) data <- data[stats::complete.cases(data[c("x", "ymin", "ymax")]), ]
     data <- data[order(data$group), ]
diff --git a/R/geom-rug.R b/R/geom-rug.R
index ffc761b91c..8992f1069d 100644
--- a/R/geom-rug.R
+++ b/R/geom-rug.R
@@ -90,7 +90,7 @@ GeomRug <- ggproto("GeomRug", Geom,
 
   draw_panel = function(self, data, panel_params, coord, lineend = "butt",
                         sides = "bl", outside = FALSE, length = unit(0.03, "npc")) {
-    data <- check_linewidth(data, snake_class(self))
+    data <- fix_linewidth(data, snake_class(self))
     check_inherits(length, "unit")
     rugs <- list()
     data <- coord$transform(data, panel_params)
diff --git a/R/geom-segment.R b/R/geom-segment.R
index 00d9eff87a..51de135b53 100644
--- a/R/geom-segment.R
+++ b/R/geom-segment.R
@@ -116,7 +116,7 @@ GeomSegment <- ggproto("GeomSegment", Geom,
                         lineend = "butt", linejoin = "round", na.rm = FALSE) {
     data$xend <- data$xend %||% data$x
     data$yend <- data$yend %||% data$y
-    data <- check_linewidth(data, snake_class(self))
+    data <- fix_linewidth(data, snake_class(self))
     data <- remove_missing(data, na.rm = na.rm,
       c("x", "y", "xend", "yend", "linetype", "linewidth"),
       name = "geom_segment"
diff --git a/R/guide-.R b/R/guide-.R
index c700329cb3..54cae7c873 100644
--- a/R/guide-.R
+++ b/R/guide-.R
@@ -19,7 +19,7 @@ NULL
 new_guide <- function(..., available_aes = "any", super) {
 
   pf <- parent.frame()
-  super <- check_subclass(super, "Guide", env = pf)
+  super <- validate_subclass(super, "Guide", env = pf)
 
   args <- list2(...)
 
@@ -51,7 +51,7 @@ new_guide <- function(..., available_aes = "any", super) {
   # Validate theme settings
   if (!is.null(params$theme)) {
     check_object(params$theme, is.theme, what = "a {.cls theme} object")
-    validate_theme(params$theme, call = caller_env())
+    check_theme(params$theme, call = caller_env())
     params$direction <- params$direction %||% params$theme$legend.direction
   }
 
diff --git a/R/labeller.R b/R/labeller.R
index 4ca220c2b4..a9ba883a79 100644
--- a/R/labeller.R
+++ b/R/labeller.R
@@ -577,21 +577,21 @@ assemble_strips <- function(grobs, theme, horizontal = TRUE, clip) {
   })
 }
 
-# Check for old school labeller
-check_labeller <- function(labeller) {
+# Repair old school labeller
+fix_labeller <- function(labeller) {
   labeller <- match.fun(labeller)
   is_deprecated <- all(c("variable", "value") %in% names(formals(labeller)))
 
   if (is_deprecated) {
+    deprecate_warn0(
+      "2.0.0", what = "facet_(labeller)",
+      details =
+      "Modern labellers do not take `variable` and `value` arguments anymore."
+    )
     old_labeller <- labeller
     labeller <- function(labels) {
       Map(old_labeller, names(labels), labels)
     }
-    # TODO Update to lifecycle after next lifecycle release
-    cli::cli_warn(c(
-      "The {.arg labeller} API has been updated. Labellers taking {.arg variable} and {.arg value} arguments are now deprecated.",
-      "i" = "See labellers documentation."
-    ))
   }
 
   labeller
diff --git a/R/layer.R b/R/layer.R
index d2355a46ba..a915763e3c 100644
--- a/R/layer.R
+++ b/R/layer.R
@@ -101,12 +101,6 @@ layer <- function(geom = NULL, stat = NULL,
                   show.legend = NA, key_glyph = NULL, layer_class = Layer) {
   call_env <- caller_env()
   user_env <- caller_env(2)
-  if (is.null(geom))
-    cli::cli_abort("Can't create layer without a geom.", call = call_env)
-  if (is.null(stat))
-    cli::cli_abort("Can't create layer without a stat.", call = call_env)
-  if (is.null(position))
-    cli::cli_abort("Can't create layer without a position.", call = call_env)
 
   # Handle show_guide/show.legend
   if (!is.null(params$show_guide)) {
@@ -125,9 +119,9 @@ layer <- function(geom = NULL, stat = NULL,
 
   data <- fortify(data)
 
-  geom <- check_subclass(geom, "Geom", env = parent.frame(), call = call_env)
-  stat <- check_subclass(stat, "Stat", env = parent.frame(), call = call_env)
-  position <- check_subclass(position, "Position", env = parent.frame(), call = call_env)
+  geom <- validate_subclass(geom, "Geom", env = parent.frame(), call = call_env)
+  stat <- validate_subclass(stat, "Stat", env = parent.frame(), call = call_env)
+  position <- validate_subclass(position, "Position", env = parent.frame(), call = call_env)
 
   # Special case for na.rm parameter needed by all layers
   params$na.rm <- params$na.rm %||% FALSE
@@ -314,17 +308,11 @@ Layer <- ggproto("Layer", NULL,
     warn_for_aes_extract_usage(aesthetics, data[setdiff(names(data), "PANEL")])
 
     # Check aesthetic values
-    nondata_cols <- check_nondata_cols(evaled)
-    if (length(nondata_cols) > 0) {
-      issues <- paste0("{.code ", nondata_cols, " = ", as_label(aesthetics[[nondata_cols]]), "}")
-      names(issues) <- rep("x", length(issues))
-      cli::cli_abort(c(
-        "Aesthetics are not valid data columns.",
-        "x" = "The following aesthetics are invalid:",
-        issues,
-        "i" = "Did you mistype the name of a data column or forget to add {.fn after_stat}?"
-      ))
-    }
+    check_nondata_cols(
+      evaled, aesthetics,
+      problem = "Aesthetics are not valid data columns.",
+      hint    = "Did you mistype the name of a data column or forget to add {.fn after_stat}?"
+    )
 
     n <- nrow(data)
     aes_n <- list_sizes(evaled)
@@ -392,17 +380,11 @@ Layer <- ggproto("Layer", NULL,
       mask = list(stage = stage_calculated)
     )
     # Check that all columns in aesthetic stats are valid data
-    nondata_stat_cols <- check_nondata_cols(stat_data)
-    if (length(nondata_stat_cols) > 0) {
-      issues <- paste0("{.code ", nondata_stat_cols, " = ", as_label(aesthetics[[nondata_stat_cols]]), "}")
-      names(issues) <- rep("x", length(issues))
-      cli::cli_abort(c(
-        "Aesthetics must be valid computed stats.",
-        "x" = "The following aesthetics are invalid:",
-        issues,
-        "i" = "Did you map your stat in the wrong layer?"
-      ))
-    }
+    check_nondata_cols(
+      stat_data, aesthetics,
+      problem = "Aesthetics must be valid computed stats.",
+      hint    = "Did you map your stat in the wrong layer?"
+    )
 
     stat_data <- data_frame0(!!!stat_data)
 
@@ -464,24 +446,26 @@ Layer <- ggproto("Layer", NULL,
   }
 )
 
-check_subclass <- function(x, subclass,
-                           argname = to_lower_ascii(subclass),
-                           env = parent.frame(),
-                           call = caller_env()) {
+validate_subclass <- function(x, subclass,
+                              argname = to_lower_ascii(subclass),
+                              x_arg = caller_arg(x),
+                              env = parent.frame(),
+                              call = caller_env()) {
+
   if (inherits(x, subclass)) {
-    x
+    return(x)
   } else if (is_scalar_character(x)) {
     name <- paste0(subclass, camelize(x, first = TRUE))
     obj <- find_global(name, env = env)
 
     if (is.null(obj) || !inherits(obj, subclass)) {
       cli::cli_abort("Can't find {argname} called {.val {x}}.", call = call)
-    } else {
-      obj
     }
-  } else {
-    stop_input_type(x, as_cli("either a string or a {.cls {subclass}} object"))
+    return(obj)
+  } else if (is.null(x)) {
+    cli::cli_abort("The {.arg {x_arg}} argument cannot be empty.", call = call)
   }
+  stop_input_type(x, as_cli("either a string or a {.cls {subclass}} object"))
 }
 
 # helper function to adjust the draw_key slot of a geom
diff --git a/R/save.R b/R/save.R
index b06c567b2e..5e1ef5983a 100644
--- a/R/save.R
+++ b/R/save.R
@@ -95,10 +95,10 @@ ggsave <- function(filename, plot = get_last_plot(),
                    dpi = 300, limitsize = TRUE, bg = NULL,
                    create.dir = FALSE,
                    ...) {
-  filename <- check_path(path, filename, create.dir)
+  filename <- validate_path(path, filename, create.dir)
 
   dpi <- parse_dpi(dpi)
-  dev <- plot_dev(device, filename, dpi = dpi)
+  dev <- validate_device(device, filename, dpi = dpi)
   dim <- plot_dim(c(width, height), scale = scale, units = units,
     limitsize = limitsize, dpi = dpi)
 
@@ -116,8 +116,8 @@ ggsave <- function(filename, plot = get_last_plot(),
   invisible(filename)
 }
 
-check_path <- function(path, filename, create.dir,
-                       call = caller_env()) {
+validate_path <- function(path, filename, create.dir,
+                          call = caller_env()) {
 
   if (length(filename) > 1 && is.character(filename)) {
     cli::cli_warn(c(
@@ -235,7 +235,7 @@ plot_dim <- function(dim = c(NA, NA), scale = 1, units = "in",
   dim
 }
 
-plot_dev <- function(device, filename = NULL, dpi = 300, call = caller_env()) {
+validate_device <- function(device, filename = NULL, dpi = 300, call = caller_env()) {
   force(filename)
   force(dpi)
 
diff --git a/R/scale-.R b/R/scale-.R
index 4bf54328b3..b2f9ef346a 100644
--- a/R/scale-.R
+++ b/R/scale-.R
@@ -622,11 +622,8 @@ Scale <- ggproto("Scale", NULL,
 )
 
 check_breaks_labels <- function(breaks, labels, call = NULL) {
-  if (is.null(breaks)) {
-    return(TRUE)
-  }
-  if (is.null(labels)) {
-    return(TRUE)
+  if (is.null(breaks) || is.null(labels)) {
+    return(invisible())
   }
 
   bad_labels <- is.atomic(breaks) && is.atomic(labels) &&
@@ -638,7 +635,7 @@ check_breaks_labels <- function(breaks, labels, call = NULL) {
     )
   }
 
-  TRUE
+  invisible()
 }
 
 default_transform <- function(self, x) {
diff --git a/R/scale-colour.R b/R/scale-colour.R
index a17d872dbe..592aa288e1 100644
--- a/R/scale-colour.R
+++ b/R/scale-colour.R
@@ -81,7 +81,6 @@
 scale_colour_continuous <- function(..., aesthetics = "colour",
                                     guide = "colourbar", na.value = "grey50",
                                     type = getOption("ggplot2.continuous.colour")) {
-
   if (!is.null(type)) {
     scale <- scale_backward_compatibility(
       ..., guide = guide, na.value = na.value, scale = type,
@@ -179,8 +178,7 @@ check_scale_type <- function(scale, name, aesthetic, scale_is_discrete = FALSE,
       "x" = "The provided scale is {scale_types[2]}."
     ), call = call)
   }
-
-  scale
+  invisible()
 }
 
 # helper function for backwards compatibility through setting defaults
@@ -241,8 +239,9 @@ scale_backward_compatibility <- function(..., scale, aesthetic, type) {
     if (!"..." %in% fn_fmls_names(scale)) {
       args <- args[intersect(names(args), fn_fmls_names(scale))]
     }
-    scale <- check_scale_type(
-      exec(scale, !!!args),
+    scale <- exec(scale, !!!args)
+    check_scale_type(
+      scale,
       paste("scale", aesthetic, type, sep = "_"),
       aesthetic,
       scale_is_discrete = type == "discrete"
diff --git a/R/scales-.R b/R/scales-.R
index 769613a2d8..87c5f6f586 100644
--- a/R/scales-.R
+++ b/R/scales-.R
@@ -154,6 +154,7 @@ ScalesList <- ggproto("ScalesList", NULL,
       return()
     }
 
+
     for (aes in new_aesthetics) {
       self$add(find_scale(aes, data[[aes]], env))
     }
diff --git a/R/theme-elements.R b/R/theme-elements.R
index 947e4e0af3..5a6b1a43cf 100644
--- a/R/theme-elements.R
+++ b/R/theme-elements.R
@@ -698,7 +698,7 @@ el_def <- function(class = NULL, inherit = NULL, description = NULL) {
 # @param el an element
 # @param elname the name of the element
 # @param element_tree the element tree to validate against
-validate_element <- function(el, elname, element_tree, call = caller_env()) {
+check_element <- function(el, elname, element_tree, call = caller_env()) {
   eldef <- element_tree[[elname]]
 
   if (is.null(eldef)) {
diff --git a/R/theme.R b/R/theme.R
index 2ebd892f62..cb7859dfe2 100644
--- a/R/theme.R
+++ b/R/theme.R
@@ -208,7 +208,7 @@
 #'   differently when added to a ggplot object. Also, when setting
 #'   `complete = TRUE` all elements will be set to inherit from blank
 #'   elements.
-#' @param validate `TRUE` to run `validate_element()`, `FALSE` to bypass checks.
+#' @param validate `TRUE` to run `check_element()`, `FALSE` to bypass checks.
 #' @export
 #' @seealso
 #'   [+.gg()] and [%+replace%],
@@ -561,12 +561,12 @@ is_theme_validate <- function(x) {
   isTRUE(validate %||% TRUE)
 }
 
-validate_theme <- function(theme, tree = get_element_tree(), call = caller_env()) {
+check_theme <- function(theme, tree = get_element_tree(), call = caller_env()) {
   if (!is_theme_validate(theme)) {
     return()
   }
   mapply(
-    validate_element, theme, names(theme),
+    check_element, theme, names(theme),
     MoreArgs = list(element_tree = tree, call = call)
   )
 }
@@ -627,7 +627,7 @@ plot_theme <- function(x, default = get_theme()) {
   theme[missing] <- ggplot_global$theme_default[missing]
 
   # Check that all elements have the correct class (element_text, unit, etc)
-  validate_theme(theme)
+  check_theme(theme)
 
   # Remove elements that are not registered
   theme[setdiff(names(theme), names(get_element_tree()))] <- NULL
diff --git a/R/utilities-help.R b/R/utilities-help.R
index 87f5419612..22bddc7dcd 100644
--- a/R/utilities-help.R
+++ b/R/utilities-help.R
@@ -2,8 +2,8 @@
 # Geoms and there's some difference among their aesthetics).
 rd_aesthetics <- function(type, name, extra_note = NULL) {
   obj <- switch(type,
-    geom = check_subclass(name, "Geom", env = globalenv()),
-    stat = check_subclass(name, "Stat", env = globalenv())
+    geom = validate_subclass(name, "Geom", env = globalenv()),
+    stat = validate_subclass(name, "Stat", env = globalenv())
   )
   aes <- rd_aesthetics_item(obj)
 
diff --git a/R/utilities.R b/R/utilities.R
index 54087eba68..9c47c78510 100644
--- a/R/utilities.R
+++ b/R/utilities.R
@@ -277,17 +277,29 @@ is.discrete <- function(x) {
   is.factor(x) || is.character(x) || is.logical(x)
 }
 
-# This function checks that all columns of a dataframe `x` are data and returns
-# the names of any columns that are not.
-# We define "data" as atomic types or lists, not functions or otherwise.
-# The `inherits(x, "Vector")` check is for checking S4 classes from Bioconductor
-# and whether they can be expected to follow behavior typical of vectors. See
-# also #3835
-check_nondata_cols <- function(x) {
-  idx <- (vapply(x, function(x) {
-    is.null(x) || rlang::is_vector(x) || inherits(x, "Vector")
-  }, logical(1)))
-  names(x)[which(!idx)]
+check_nondata_cols <- function(data, mapping, problem = NULL, hint = NULL) {
+  # We define "data" as atomic types or lists, not functions or otherwise.
+  # The `inherits(x, "Vector")` check is for checking S4 classes from Bioconductor
+  # and whether they can be expected to follow behaviour typical of vectors. See
+  # also #3835
+  invalid <- which(!vapply(
+    data, FUN.VALUE = logical(1),
+    function(x) is.null(x) || rlang::is_vector(x) || inherits(x, "Vector")
+  ))
+  invalid <- names(data)[invalid]
+
+  if (length(invalid) < 1) {
+    return(invisible())
+  }
+
+  mapping <- vapply(mapping[invalid], as_label, character(1))
+  issues <- paste0("{.code ", invalid, " = ", mapping, "}")
+  names(issues) <- rep("*", length(issues))
+  issues <- c(x = "The following aesthetics are invalid:", issues)
+
+  # Using 'call = NULL' here because `by_layer()` does a good job of indicating
+  # the origin of the error
+  cli::cli_abort(c(problem, issues, i = hint), call = NULL)
 }
 
 compact <- function(x) {
diff --git a/tests/testthat/_snaps/facet-.md b/tests/testthat/_snaps/facet-.md
index 17d76b1f86..154499e38a 100644
--- a/tests/testthat/_snaps/facet-.md
+++ b/tests/testthat/_snaps/facet-.md
@@ -3,7 +3,7 @@
     Code
       facet_wrap(aes(foo))
     Condition
-      Error in `validate_facets()`:
+      Error in `check_vars()`:
       ! Please use `vars()` to supply facet variables.
 
 ---
@@ -11,7 +11,7 @@
     Code
       facet_grid(aes(foo))
     Condition
-      Error in `validate_facets()`:
+      Error in `check_vars()`:
       ! Please use `vars()` to supply facet variables.
 
 # facet_grid() fails if passed both a formula and a vars()
@@ -73,7 +73,7 @@
       Error:
       ! object 'no_such_variable' not found
 
-# validate_facets() provide meaningful errors
+# check_vars() provide meaningful errors
 
     Please use `vars()` to supply facet variables.
 
diff --git a/tests/testthat/_snaps/facet-labels.md b/tests/testthat/_snaps/facet-labels.md
index 6cdd9c1ad0..525e0dd0b7 100644
--- a/tests/testthat/_snaps/facet-labels.md
+++ b/tests/testthat/_snaps/facet-labels.md
@@ -16,6 +16,6 @@
 
 # old school labellers still work
 
-    The `labeller` API has been updated. Labellers taking `variable` and `value` arguments are now deprecated.
-    i See labellers documentation.
+    The `labeller` argument of `facet_()` is deprecated as of ggplot2 2.0.0.
+    i Modern labellers do not take `variable` and `value` arguments anymore.
 
diff --git a/tests/testthat/_snaps/fortify.md b/tests/testthat/_snaps/fortify.md
index 2034f092fb..605829d9d8 100644
--- a/tests/testthat/_snaps/fortify.md
+++ b/tests/testthat/_snaps/fortify.md
@@ -10,7 +10,7 @@
     Condition
       Error in `fortify()`:
       ! `data` must be a <data.frame>, or an object coercible by `fortify()`, or a valid <data.frame>-like object coercible by `as.data.frame()`.
-      Caused by error in `.prevalidate_data_frame_like_object()`:
+      Caused by error in `check_data_frame_like()`:
       ! `dim(data)` must return an <integer> of length 2.
 
 ---
@@ -20,7 +20,7 @@
     Condition
       Error in `fortify()`:
       ! `data` must be a <data.frame>, or an object coercible by `fortify()`, or a valid <data.frame>-like object coercible by `as.data.frame()`.
-      Caused by error in `.prevalidate_data_frame_like_object()`:
+      Caused by error in `check_data_frame_like()`:
       ! `dim(data)` must return an <integer> of length 2.
 
 ---
@@ -30,7 +30,7 @@
     Condition
       Error in `fortify()`:
       ! `data` must be a <data.frame>, or an object coercible by `fortify()`, or a valid <data.frame>-like object coercible by `as.data.frame()`.
-      Caused by error in `.prevalidate_data_frame_like_object()`:
+      Caused by error in `check_data_frame_like()`:
       ! `colnames(data)` must return a <character> of length `ncol(data)`.
 
 ---
@@ -50,7 +50,7 @@
     Condition
       Error in `fortify()`:
       ! `data` must be a <data.frame>, or an object coercible by `fortify()`, or a valid <data.frame>-like object coercible by `as.data.frame()`.
-      Caused by error in `.prevalidate_data_frame_like_object()`:
+      Caused by error in `check_data_frame_like()`:
       ! `dim(data)` must return an <integer> of length 2.
 
 ---
@@ -60,7 +60,7 @@
     Condition
       Error in `fortify()`:
       ! `data` must be a <data.frame>, or an object coercible by `fortify()`, or a valid <data.frame>-like object coercible by `as.data.frame()`.
-      Caused by error in `.prevalidate_data_frame_like_object()`:
+      Caused by error in `check_data_frame_like()`:
       ! `dim(data)` must return an <integer> of length 2.
 
 ---
@@ -70,7 +70,7 @@
     Condition
       Error in `fortify()`:
       ! `data` must be a <data.frame>, or an object coercible by `fortify()`, or a valid <data.frame>-like object coercible by `as.data.frame()`.
-      Caused by error in `.prevalidate_data_frame_like_object()`:
+      Caused by error in `check_data_frame_like()`:
       ! `dim(data)` can't have `NA`s or negative values.
 
 ---
@@ -80,7 +80,7 @@
     Condition
       Error in `fortify()`:
       ! `data` must be a <data.frame>, or an object coercible by `fortify()`, or a valid <data.frame>-like object coercible by `as.data.frame()`.
-      Caused by error in `.prevalidate_data_frame_like_object()`:
+      Caused by error in `check_data_frame_like()`:
       ! `dim(data)` can't have `NA`s or negative values.
 
 ---
@@ -100,7 +100,7 @@
     Condition
       Error in `fortify()`:
       ! `data` must be a <data.frame>, or an object coercible by `fortify()`, or a valid <data.frame>-like object coercible by `as.data.frame()`.
-      Caused by error in `.prevalidate_data_frame_like_object()`:
+      Caused by error in `check_data_frame_like()`:
       ! `colnames(data)` must return a <character> of length `ncol(data)`.
 
 ---
@@ -110,7 +110,7 @@
     Condition
       Error in `fortify()`:
       ! `data` must be a <data.frame>, or an object coercible by `fortify()`, or a valid <data.frame>-like object coercible by `as.data.frame()`.
-      Caused by error in `.prevalidate_data_frame_like_object()`:
+      Caused by error in `check_data_frame_like()`:
       ! `colnames(data)` must return a <character> of length `ncol(data)`.
 
 ---
@@ -130,7 +130,7 @@
     Condition
       Error in `fortify()`:
       ! `data` must be a <data.frame>, or an object coercible by `fortify()`, or a valid <data.frame>-like object coercible by `as.data.frame()`.
-      Caused by error in `.postvalidate_data_frame_like_object()`:
+      Caused by error in `check_data_frame_conversion()`:
       ! `as.data.frame(data)` must return a <data.frame>.
 
 ---
@@ -140,7 +140,7 @@
     Condition
       Error in `fortify()`:
       ! `data` must be a <data.frame>, or an object coercible by `fortify()`, or a valid <data.frame>-like object coercible by `as.data.frame()`.
-      Caused by error in `.postvalidate_data_frame_like_object()`:
+      Caused by error in `check_data_frame_conversion()`:
       ! `as.data.frame(data)` must preserve dimensions.
 
 ---
@@ -150,6 +150,6 @@
     Condition
       Error in `fortify()`:
       ! `data` must be a <data.frame>, or an object coercible by `fortify()`, or a valid <data.frame>-like object coercible by `as.data.frame()`.
-      Caused by error in `.postvalidate_data_frame_like_object()`:
+      Caused by error in `check_data_frame_conversion()`:
       ! `as.data.frame(data)` must preserve column names.
 
diff --git a/tests/testthat/_snaps/geom-.md b/tests/testthat/_snaps/geom-.md
index 0eae2d74ba..b0ca0c7e85 100644
--- a/tests/testthat/_snaps/geom-.md
+++ b/tests/testthat/_snaps/geom-.md
@@ -2,10 +2,10 @@
 
     Problem while setting up geom aesthetics.
     i Error occurred in the 1st layer.
-    Caused by error in `use_defaults()`:
-    ! Aesthetic modifiers returned invalid values
-    x The following mappings are invalid
-    x `colour = after_scale(data)`
+    Caused by error:
+    ! Aesthetic modifiers returned invalid values.
+    x The following aesthetics are invalid:
+    * `colour = after_scale(data)`
     i Did you map the modifier in the wrong layer?
 
 ---
diff --git a/tests/testthat/_snaps/ggsave.md b/tests/testthat/_snaps/ggsave.md
index 372d324b95..03440c5eba 100644
--- a/tests/testthat/_snaps/ggsave.md
+++ b/tests/testthat/_snaps/ggsave.md
@@ -58,7 +58,7 @@
 ---
 
     Code
-      plot_dev("xyz")
+      validate_device("xyz")
     Condition
       Error:
       ! Unknown graphics device "xyz"
@@ -66,7 +66,7 @@
 ---
 
     Code
-      plot_dev(NULL, "test.xyz")
+      validate_device(NULL, "test.xyz")
     Condition
       Error:
       ! Unknown graphics device "xyz"
diff --git a/tests/testthat/_snaps/layer.md b/tests/testthat/_snaps/layer.md
index 70573a3d7c..79b561b17d 100644
--- a/tests/testthat/_snaps/layer.md
+++ b/tests/testthat/_snaps/layer.md
@@ -1,14 +1,14 @@
 # layer() checks its input
 
-    Can't create layer without a geom.
+    The `geom` argument cannot be empty.
 
 ---
 
-    Can't create layer without a stat.
+    The `stat` argument cannot be empty.
 
 ---
 
-    Can't create layer without a position.
+    The `position` argument cannot be empty.
 
 ---
 
@@ -43,20 +43,20 @@
 
     Problem while computing aesthetics.
     i Error occurred in the 1st layer.
-    Caused by error in `compute_aesthetics()`:
+    Caused by error:
     ! Aesthetics are not valid data columns.
     x The following aesthetics are invalid:
-    x `fill = data`
+    * `fill = data`
     i Did you mistype the name of a data column or forget to add `after_stat()`?
 
 ---
 
     Problem while mapping stat to aesthetics.
     i Error occurred in the 1st layer.
-    Caused by error in `map_statistic()`:
+    Caused by error:
     ! Aesthetics must be valid computed stats.
     x The following aesthetics are invalid:
-    x `fill = after_stat(data)`
+    * `fill = after_stat(data)`
     i Did you map your stat in the wrong layer?
 
 # missing aesthetics trigger informative error
@@ -85,22 +85,22 @@
 
     Problem while computing aesthetics.
     i Error occurred in the 1st layer.
-    Caused by error in `compute_aesthetics()`:
+    Caused by error:
     ! Aesthetics are not valid data columns.
     x The following aesthetics are invalid:
-    x `colour = NULL`
-    x `fill = NULL`
+    * `colour = density`
+    * `fill = density`
     i Did you mistype the name of a data column or forget to add `after_stat()`?
 
 # computed stats are in appropriate layer
 
     Problem while mapping stat to aesthetics.
     i Error occurred in the 1st layer.
-    Caused by error in `map_statistic()`:
+    Caused by error:
     ! Aesthetics must be valid computed stats.
     x The following aesthetics are invalid:
-    x `colour = NULL`
-    x `fill = NULL`
+    * `colour = after_stat(density)`
+    * `fill = after_stat(density)`
     i Did you map your stat in the wrong layer?
 
 # layer reports the error with correct index etc
diff --git a/tests/testthat/test-facet-.R b/tests/testthat/test-facet-.R
index 11e86247ca..a24a5e4ca5 100644
--- a/tests/testthat/test-facet-.R
+++ b/tests/testthat/test-facet-.R
@@ -469,9 +469,9 @@ test_that("eval_facet() is tolerant for missing columns (#2963)", {
   )
 })
 
-test_that("validate_facets() provide meaningful errors", {
-  expect_snapshot_error(validate_facets(aes(var)))
-  expect_snapshot_error(validate_facets(ggplot()))
+test_that("check_vars() provide meaningful errors", {
+  expect_snapshot_error(check_vars(aes(var)))
+  expect_snapshot_error(check_vars(ggplot()))
 })
 
 test_that("check_layout() throws meaningful errors", {
diff --git a/tests/testthat/test-ggsave.R b/tests/testthat/test-ggsave.R
index 4180eadc98..158dae2594 100644
--- a/tests/testthat/test-ggsave.R
+++ b/tests/testthat/test-ggsave.R
@@ -125,19 +125,19 @@ test_that("scale multiplies height & width", {
 # plot_dev ---------------------------------------------------------------------
 
 test_that("unknown device triggers error", {
-  expect_snapshot_error(plot_dev(1))
-  expect_snapshot(plot_dev("xyz"), error = TRUE)
-  expect_snapshot(plot_dev(NULL, "test.xyz"), error = TRUE)
+  expect_snapshot_error(validate_device(1))
+  expect_snapshot(validate_device("xyz"), error = TRUE)
+  expect_snapshot(validate_device(NULL, "test.xyz"), error = TRUE)
 })
 
 
 test_that("text converted to function", {
-  expect_identical(body(plot_dev("png"))[[1]], quote(png_dev))
-  expect_identical(body(plot_dev("pdf"))[[1]], quote(grDevices::pdf))
+  expect_identical(body(validate_device("png"))[[1]], quote(png_dev))
+  expect_identical(body(validate_device("pdf"))[[1]], quote(grDevices::pdf))
 })
 
 test_that("if device is NULL, guess from extension", {
-  expect_identical(body(plot_dev(NULL, "test.png"))[[1]], quote(png_dev))
+  expect_identical(body(validate_device(NULL, "test.png"))[[1]], quote(png_dev))
 })
 
 # parse_dpi ---------------------------------------------------------------
diff --git a/tests/testthat/test-layer.R b/tests/testthat/test-layer.R
index 225cedd947..59970c7db5 100644
--- a/tests/testthat/test-layer.R
+++ b/tests/testthat/test-layer.R
@@ -8,8 +8,8 @@ test_that("layer() checks its input", {
   expect_snapshot_error(layer("point", "identity", mapping = 1:4, position = "identity"))
   expect_snapshot_error(layer("point", "identity", mapping = ggplot(), position = "identity"))
 
-  expect_snapshot_error(check_subclass("test", "geom"))
-  expect_snapshot_error(check_subclass(environment(), "geom"))
+  expect_snapshot_error(validate_subclass("test", "geom"))
+  expect_snapshot_error(validate_subclass(environment(), "geom"))
 })
 
 test_that("aesthetics go in aes_params", {
diff --git a/tests/testthat/test-scales-breaks-labels.R b/tests/testthat/test-scales-breaks-labels.R
index 42e3d67bb3..e0b8474a40 100644
--- a/tests/testthat/test-scales-breaks-labels.R
+++ b/tests/testthat/test-scales-breaks-labels.R
@@ -12,8 +12,8 @@ test_that("labels match breaks", {
 })
 
 test_that("labels don't have to match null breaks", {
-  expect_true(check_breaks_labels(breaks = 1:3, labels = NULL))
-  expect_true(check_breaks_labels(breaks = NULL, labels = 1:2))
+  expect_silent(check_breaks_labels(breaks = 1:3, labels = NULL))
+  expect_silent(check_breaks_labels(breaks = NULL, labels = 1:2))
 })
 
 test_that("labels don't have extra spaces", {
diff --git a/tests/testthat/test-theme.R b/tests/testthat/test-theme.R
index ef358b10b6..81e08f18f8 100644
--- a/tests/testthat/test-theme.R
+++ b/tests/testthat/test-theme.R
@@ -250,7 +250,7 @@ test_that("complete and non-complete themes interact correctly with ggplot objec
   expect_equal(p$plot$theme$text$face, "italic")
 })
 
-test_that("theme(validate=FALSE) means do not validate_element", {
+test_that("theme(validate=FALSE) means do not check_element", {
   p <- ggplot(data.frame(x = 1:3), aes(x, x)) + geom_point()
   bw <- p + theme_bw()
   red.text <- theme(text = element_text(colour = "red"))
@@ -516,9 +516,9 @@ test_that("Theme elements are checked during build", {
 
 test_that("Theme validation behaves as expected", {
   tree <- get_element_tree()
-  expect_silent(validate_element(1,  "aspect.ratio", tree))
-  expect_silent(validate_element(1L, "aspect.ratio", tree))
-  expect_snapshot_error(validate_element("A", "aspect.ratio", tree))
+  expect_silent(check_element(1,  "aspect.ratio", tree))
+  expect_silent(check_element(1L, "aspect.ratio", tree))
+  expect_snapshot_error(check_element("A", "aspect.ratio", tree))
 })
 
 test_that("Element subclasses are inherited", {