diff --git a/bin/jekyll b/bin/jekyll
index 01f97cf9..fe61508e 100755
--- a/bin/jekyll
+++ b/bin/jekyll
@@ -12,7 +12,7 @@ program :name, 'jekyll'
 program :version, Jekyll::VERSION
 program :description, 'Jekyll is a blog-aware, static site generator in Ruby'
 
-default_command :help
+default_command :default
 
 global_option '-s', '--source [DIR]', 'Source directory (defaults to ./)'
 global_option '-d', '--destination [DIR]', 'Destination directory (defaults to ./_site)'
@@ -33,6 +33,16 @@ def normalize_options(options)
   options
 end
 
+command :default do |c|
+  c.action do |args, options|
+    if args.empty?
+      command(:help).run
+    else
+      Jekyll.logger.abort_with "Invalid command. Use --help for more information"
+    end
+  end
+end
+
 command :new do |c|
   c.syntax = 'jekyll new PATH'
   c.description = 'Creates a new Jekyll site scaffold in PATH'
diff --git a/lib/jekyll/stevenson.rb b/lib/jekyll/stevenson.rb
index 5be5f04c..b825cea5 100644
--- a/lib/jekyll/stevenson.rb
+++ b/lib/jekyll/stevenson.rb
@@ -5,7 +5,7 @@ module Jekyll
     DEBUG  = 0
     INFO   = 1
     WARN   = 2
-    ERROR = 3
+    ERROR  = 3
 
     # Public: Create a new instance of Stevenson, Jekyll's logger
     #
@@ -22,7 +22,7 @@ module Jekyll
     # message - the message detail
     #
     # Returns nothing
-    def info(topic, message)
+    def info(topic, message = nil)
       $stdout.puts(message(topic, message)) if log_level <= INFO
     end
 
@@ -32,7 +32,7 @@ module Jekyll
     # message - the message detail
     #
     # Returns nothing
-    def warn(topic, message)
+    def warn(topic, message = nil)
       $stderr.puts(message(topic, message).yellow) if log_level <= WARN
     end
 
@@ -42,10 +42,21 @@ module Jekyll
     # message - the message detail
     #
     # Returns nothing
-    def error(topic, message)
+    def error(topic, message = nil)
       $stderr.puts(message(topic, message).red) if log_level <= ERROR
     end
 
+    # Public: Print a Jekyll error message to stderr and immediately abort the process
+    #
+    # topic - the topic of the message, e.g. "Configuration file", "Deprecation", etc.
+    # message - the message detail (can be omitted)
+    #
+    # Returns nothing
+    def abort_with(topic, message = nil)
+      error(topic, message)
+      abort
+    end
+
     # Public: Build a Jekyll topic method
     #
     # topic - the topic of the message, e.g. "Configuration file", "Deprecation", etc.