Aristotle emphasized that ethical conduct requires practice so that it become a habit. In addition, aristotle is a greek philosopher which emphasized the difference among nature on the one hand and law, custom or convention on the other. A law of nature would so have had the flavor more of a paradox than something that obviously existed. In contrast to the conventionalism that the difference among nature and custom could engender socrates and his philosophic successors plato and aristotle, postulated the presence of natural justice or natural right. Therefore, aristotle is often said to be the father of natural law.