The article attempts to show that the concept of sympathy, taken from Adam Smith’s Theory of Moral Sentiments, allows us to distinguish between the purely egoistic interest (‘selfishness’) of the homo oeconomicus theories (which we describe as ‘autistic’) and an interest in oneself (‘self-love’), which stems from a sympathy towards ourselves (‘reflexive sympathy’) built from the sympathy we feel towards the other (‘direct sympathy’) and from the other towards us (‘reciprocal sympathy’). Interest, in the sense of self-love, by being part of the loops of sympathy, allows us to get out of the theoretical deadlocks that we can find in some authors of the seventeenth and eighteenth centuries, including those already criticised by Smith : Mandeville, Hume, Hutcheson, and Hobbes, the one on whom we are focusing. We then broaden our analysis by relying on the recent discoveries of mirror neurons which enable us to explain empathy (a concept very close to Smithian ‘sympathy’) in humans as well as in the great apes. As empathy now has an indisputable neurological basis, it allows us to confirm our critique of the standard economic theories of homo oeconomicus and to contemplate a re-foundation of political economy.