Aristotle's Ethic, Descriptive or applied A Clash between Descartes and Aristotle's ethic Hasan Mehrnia Assistant professor of the University of Tehran Hmehrnia@ut.ac.ir Abstract: Descartes in one of his most influential works, i.e. Discours de la méthode, besides criticizing the method and ethical doctrines of ancient thinkers, especially Aristotle; and accusing them to exaggeration and overstating in their ethical system, has promised, contrary to Aristotle, to prepare a real step ladder for climbing up from his new ethical mansion. He believes that Aristotle's ethic had failed to transcend us to the top of this huge building and in fact has nothing more than some descriptive useless ethical rules. In this paper, we will demonstrate that: Firstly, Descartes was not true in his clams against Scholastic thought and especially in criticizing Aristotle's ethical doctrines. Moreover, he had no choice except using Aristotle's ethical doctrines in his system as much as he could. Secondly, the actualization of a fundamental ethical building which he had promised in his works, could never take place and remain only an imaginary project for him. Thirdly, although when Aristotle's ideas about ethic in modern world take more precisely into consideration, because of its emphasis on virtue, looks like an imaginary ethic which is to some extent far from our real life, but it does not mean that we should abandon its golden rules and appeal only to Jeremy Bentham's utilitarian ethic or until to Kant's deontological ethic. So, both Aristotle and Plato even now have located at the top of each metaphysical system and ethical life. Keywords: theoretical wisdom, practical wisdom, ethic, will, reason.