Aristotle, probably the greatest teacher who ever lived, surveyed in his "Ethics" the ends to which conduct should be directed. The importance of this work to a modern reader lies in Aristotle's boldness in introducing psychology into his study of human behaviour. He extended the frontiers of philosophy to include universal science, by converting ethics from a theoretical to a practical science, based on a careful observation of life and a genuine understanding of human nature. The "Ethics", the substance of lectures delivered to Aristotle's students is lucidly translated for the Penguin Classics by J. A. K. tTomson.