This article is from the Object-Oriented Technology FAQ, by Bob Hathaway email@example.com with numerous contributions by others.
In the authors opinion, a myth. The story goes an object is an instance of a
class (Meta-Object), a class is an instance of a Meta-Class, which must also
be an instance of a Meta-Meta-Class, which must also be an instance of a Meta-
Meta-Meta-Class, ... Closure can be achieved with an instance-of loop, as with
a Meta-Class being an instance of itself or with a "Meta-Class - Meta-Class
class" instance-of loop (as in Smalltalk).