A person finds a lost purse with a lot of money in it. Ought she try to return it to its owner or keep it herself? And even more interestingly, what will she actually do? According to standard economic theory, a rational person is supposed to maximize her utility and, at least when unobserved, keep the purse for herself. In reality, however, most people return the purse although they are unobserved or, at least, they feel uneasy about not doing so. Evidently, these people share a common attitude towards other people's property. In social life, norms and values like this typically help in...