The adaptive importance of cognitive efficiency: an alternative theory of why we have beliefs and desires

Finding out why we have beliefs and desires is important for a thorough understanding of the nature of our minds (and those of other animals). It is therefore unsurprising that several accounts have been presented that are meant to answer this question. At least in the philosophical literature, the most widely accepted of these are due to Kim Sterelny and Peter Godfrey-Smith, who argue that beliefs and desires evolved due to their enabling us to be behaviourally flexible in a way that reflexes do not—which, they claim, is beneficial in epistemically complex environments. However, as I try to make clear in this paper, upon closer consideration, this kind of account turns out to be theoretically implausible. In the main, this is because it fails to give due credit to the powers of reflex-driven organisms, which can in fact be just as flexible in their behaviour as ones that are belief/desire-driven. In order to improve on this account, I therefore propose that beliefs and desires evolved, not due to their enabling us to do something completely different from what reflexive organisms can do, but rather due to their enabling us to do the same things better. Specifically, I argue that beliefs and desires evolved for making the generation of behaviour more efficient, since they can simplify the necessary cognitive labour considerably. I end by considering various implications of this account.