What others believe about me makes a difference to whether I succeed in some of my main projects in life: it determines whether I have a good reputation and whether I participate in genuine friendships, among other things. What others believe about me can therefore make a (non-instrumental) difference to my well-being. How you regulate your beliefs can then affect the well-being of others, and sometimes, that effect on well-being is independent of considerations of the evidence. Usually, you do not have an obligation to regulate your beliefs in response to the interests of others, but you do have reasons to regulate your beliefs in response to the interests of your friends – at least sometimes, within some (perfectly good) friendships. There are then reasons for belief that sometimes compete with reasons provided by evidence. This conclusion has some consequences for applied epistemology, but some for the ethics of friendship. It suggests that the best friendships are not necessarily those that exist between perfectly virtuous friends. The function of friendship, often, is to help us cope with the fact that we are not perfectly virtuous, and that we have needs that the perfectly virtuous person does not share.