Lambda the Ultimate

And Shin-Cheng Mu gives a rather accessible algebraic proof.

There's lots to say about this observation, but apart from saying I was surprised by it, I will leave comment to the comments.

Does anyone here know the origin of the term "multimethod"?

I would guess that the term "multiple dispatch" sprang from common OO dispatch table (or vtable) implementation of single dispatch, and carries the OO bias of a "this" argument (no point saying "multiple" without a "single" as an assumed baseline). Does the "multi-" in "multimethod" stem from similar thinking or from a more functional orientation (perhaps the "multi" meant to suggest the several function implementations that may be invoked by a given function call)?