I've met some people who have stated beliefs that seem, in my opinion, to be "crazy" (not literally mentally ill, just 'out there') and in my opinion almost certainly wrong. But these same people, in domains in which one would expect these beliefs to influence their actions, act reasonably. This suggests several interesting possibilities; among them: (a) I may be wrong; (b) the person's beliefs, when stated alone, sound crazy, but this is because the other beliefs of the person, and possibly even the vocabulary the person uses, is unconventional; if i truly understood the context of all the other person's beliefs i would interpret what they say much differently and not think it was crazy.

However, my favorite explanation is (c) that it may be common for people to act reasonably even while holding relevant beliefs that seem crazy -- if this is true, then how this could be is an important question for cognitive studies. A consequence of this would be that one should not underestimate someone who has some crazy beliefs -- not because the beliefs might be right, but because the wrongness of their beliefs may not cause their actions to be very suboptimal.