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Message: [QUOTE="Greg Weeks, post: 4584720"] Ruby exposes its singleton meta-classes, eg: class <<B ; $Meta_B = self ; end But their relationships are not quite what I expected. For example: Suppose that A inherits from B (and B inherits from Object). Of course, this means that A instances respond to all the B instance messages. So: A.new.is_a? B -> true At the same time, the A class object responds to all the B class object messages. So: class <<Object ; $Meta_Object = self ; end class <<B ; $Meta_B = self ; end class <<A ; $Meta_A = self ; end A.is_a? $Meta_A -> true B.is_a? $Meta_A -> false A.is_a? $Meta_B -> true B.is_a? $Meta_B -> true Since everything that is_a $Meta_A also is_a $Meta_B, I expected a subclass/superclass relationship. Indeed, I expected the following to be true: $Meta_A.superclass == $Meta_B $Meta_B.superclass == $Meta_Object $Meta_Object.superclass == Class Class.superclass == Module Module.superclass == Object Object.superclass == nil The above superclass chain reflects how a message to the class A object is looked up. What surprised me is that the first two equalities above are false. Should they have been true? FWIW: The superclass of both $Meta_A and $Meta_B is something called #<Class:Class>, which is its own superclass and is a subclass of $Meta_Object: $X = $Meta_A.superclass -> #<Class:Class> $X == $Meta_B.superclass -> true $X == $X.superclass -> true $X < $Meta_Object -> true [/QUOTE]