You will want to read this[1] and the links in there. (And note the names of those involved in the thread; those were the days...)

[1] http://people.csail.mit.edu/gregs/ll1-discuss-archive-html/m...

A lot of people would disagree, and hence the koan.

Personally, I see closures as objects that the compiler cooks up on your behalf. This coming from a compiler background, where said compiler is usually implemented in C++ :P.