A rational belief isn't necessarily correct or true. Rational beliefs are justified, in that they logically follow from premises that are accepted as true. In the case of probabilistic statements, a rational strategy is one that maximizes the chance of being correct or otherwise reaching a defined goal state. It doesn't have to work or be correct in any ultimate sense to be rational.

If I play the lottery and win, playing the lottery turned out to be a way to get lots of money. It doesn't mean that playing the lottery was a rational strategy. If I make a reasonable investment and improbable misfortune strikes, losing the money, that doesn't mean that the investment wasn't rational.

This has no bearing on the point above. In essence you're just rephrasing Robin's definition, "better believing what is true, given one's limited info and analysis resources." The disposition best-calculated to lead to true beliefs will not produce true beliefs in every instance, because true beliefs will not always be justified by available evidence.

So what?

The Costs of Rationality

by RobinHanson 1 min read3rd Mar 200981 comments

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The word "rational" is overloaded with associations, so let me be clear: to me [here], more "rational" means better believing what is true, given one's limited info and analysis resources. 

Rationality certainly can have instrumental advantages.  There are plenty of situations where being more rational helps one achieve a wide range of goals.  In those situtations, "winnners", i.e., those who better achieve their goals, should tend to be more rational.  In such cases, we might even estimate someone's rationality by looking at his or her "residual" belief-mediated success, i.e., after explaining that success via other observable factors.

But note: we humans were designed in many ways not to be rational, because believing the truth often got in the way of achieving goals evolution had for us.  So it is important for everyone who intends to seek truth to clearly understand: rationality has costs, not only in time and effort to achieve it, but also in conflicts with other common goals.

Yes, rationality might help you win that game or argument, get promoted, or win her heart.  Or more rationality for you might hinder those outcomes.  If what you really want is love, respect, beauty, inspiration, meaning, satisfaction, or success, as commonly understood, we just cannot assure you that rationality is your best approach toward those ends.  In fact we often know it is not.

The truth may well be messy, ugly, or dispriting; knowing it make you less popular, loved, or successful.  These are actually pretty likely outcomes in many identifiable situations.  You may think you want to know the truth no matter what, but how sure can you really be of that?  Maybe you just like the heroic image of someone who wants the truth no matter what; or maybe you only really want to know the truth if it is the bright shining glory you hope for. 

Be warned; the truth just is what it is.  If just knowing the truth is not reward enough, perhaps you'd be better off not knowing.  Before you join us in this quixotic quest, ask yourself: do you really want to be generally rational, on all topics?  Or might you be better off limiting your rationality to the usual practical topics where rationality is respected and welcomed?

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