ahh btw to satisfy the citation request:

Computer chess on wikipedia

I've participated some in computer contests, not chess related, where you can't solve the problem exactly. It's generally the case that you need clever "substitutions" to get anywhere at all. Most problems that aren't outright trivial are too hard to solve from first principles.

Definitely so for the real world behaviours. A supposedly 'rational' calculation of best move, from first principles (death of king), but without substitutions and hunch based heuristics, done by human, over course of centuries, will not be even remotely powerful enough to match the immediate move that Kasparov would somehow make playing 1-minute blitz (and if you actually played chess real fast, it does become apparent that you just can't match this play without massively parallel, rather deep evaluation). I think all aspiring rationalists should learn boardgames like Chess, Go, and perhaps some RTS (like starcraft, though my favourite is springrts. In the starcraft the AI has too much advantage due to human bottlenecking on the output) to appreciate the difficulties. Ideally, try writing an AI that fights against other AIs (in a timed programming contest) to appreciate the issues with advance metastrategies and heuristics.

I perform best on that sort of stuff if I am not tired and I act on feelings. If I am tired or bored and I act on feelings that leads to a quick loss which is also rational because - what the hell am I doing playing game when tired?

edit: where the hell did my wikipedia link disappear? ahh nevermind.