Commentators commonly assume that Descartes regards it as a function of the passions to inform us or teach us which things are beneficial and which are harmful. As a result, they tend to infer that Descartes regards the passions as an appropriate guide to what is beneficial or harmful. In this paper I argue that this conception of the role of the passions in Descartes is mistaken. First, in spite of a number of texts appearing to show the contrary, I (...) argue that Descartes does not regard it as the role of the passions to inform us about what is beneficial or harmful. Second, although Descartes calls the passions good and useful, I argue that Descartes does not think we should allow ourselves to be guided by them. When we recognize that the function of the passions is largely motivational and not informative, we can more easily understand Descartes's practical advice in The Passions of the Soul that happiness requires us to guide our passions instead of letting our passions guide us. (shrink)