Sometimes, apparently rational self-interested strategies turn out (as in the prisoners' dilemma) to be self-defeating. This may look like a defeat for rationality, but it is not. Rationality is saved by its own open-endedness. If a strategy of following accepted rules of rationality is sometimes self-defeating, this is not the end. We revise the rules to take account of this, so producing a higher-order rationality strategy. This in turn may fail, but again we go up a level. At whatever level we fail, there is always the process of standing back and going up a further level.

Quoted in The Blank Slate by Steven Pinker