Klein Bottle

When I was in high school, or perhaps even as early as junior high, I discovered geometric topology (algebraic topology is a tad tougher to grok), in the form of various conundra. Prime among equals was the Klein bottle.

... informally, it is a surface (a two-dimensional manifold) in which notions of left and right cannot be consistently defined.

Lawrence Klein, on the other hand, certainly knew left from right. He was, on the whole, of the left.

And, contrary to certain mealy-mouthed economists of late (nudge, nudge; go read recent musings):

"The only satisfactory test of economics is the ability to predict," he wrote.