Spinoza's philosophy has much in common with Stoicism inasmuch as both philosophies sought to fulfil a therapeutic role by instructing people how to attain happiness. Spinoza, however, differed sharply from the Stoics in one important respect: He utterly rejected their contention that reason could defeat emotion. On the contrary, he contended, an emotion can only be displaced or overcome by a stronger emotion. For him, the crucial distinction was between active and passive emotions, the former being those that are rationally understood and the latter those that are not. He also held that knowledge of true causes of passive emotion can transform it to an active emotion, thus anticipating one of the key ideas of Sigmund Freud's psychoanalysis.