One problem, surely, in real life is not knowing what the other person's "utility function" is? So someone may behave apparently irrationally - e.g. giving away money - because their utility function involves making themselves feel good, or getting a reward in heaven, or they want to show off how generous they are to impress someone, or something else we don't know. So in practice it isn't even theoretically possible to know if someone else is behaving rationally a lot of the time.
Personally, I think anyone without brain damage or mental illness will normally behave rationally according to their own lights. We call it cognitive dissonance when someone is unable to justify their beliefs or actions - they have found some contradiction within themselves - but they usually quickly act to reduce this, by changing their beliefs or doing something different. And it doesn't seem to happen very often, as far as I know, so it seems to me that most people are acting rationally according to their own utility functions most of the time. By the way, I don't see how a random decision can be considered "irrational by definition". To say something is rational surely means there is a reason for doing it which "attempts to maximise the person's utility function" - so making a random decision is rational so long as there is a good reason to do so - e.g. neither option seemed better, or a "leftfield" move confounded an opponent, or it was more important to make *some* decision quickly than to work out the best decision (as in the chess clock example) etc. -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to email@example.com. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/groups/opt_out.