The most important question we can ask is about how things relate to purpose. Aristotle believed that everything had a purpose. He believed that humans are the only creatures who can think (and reason); their purpose is to use their ability. We achieve our true purpose when we think: "I think therefore I am," in the words of Descartes. In Buddhism, however, true peace is derived not from thinking about something, but from thinking about nothing—or being in a state of "suchness"-- an absolute void. For Aristotle, and later Aquinas, there is design and order in the universe; things happen according to purpose and in an orderly way. For Aristotle, we can understand the universe (world) by studying it in terms of purpose. For Aquinas, we can understand God by knowing His purpose. When we go against purpose, for both philosophers, we suffer the consequences. For Aristotle the person who follows a purpose leads a rational life of moderation—and thus is derived the search for the "golden mean," a compromise between extremes.