"The philosophy asserts that virtue (meaning, chiefly, the four cardinal virtues of self-control, courage , justice , and wisdom) is happiness, and it is our perceptions of things-- rather than the things themselves-- that cause most of our trouble. Stoicism teaches that we can't control or rely on anything outside what Epictetus called our "reasoned choice"-- our ability to use our reason to choose how we categorize, respond, and reorient ourselves to external events."