InThe Metaphysics, Aristotle laid the foundations for one of the central branches of Western philosophy.The son of a doctor and an eminent scientist in his own right, Aristotle was always passionately interested in natural phenomena. Yet when he joined Plato's Academy as a seventeen-year-old in the mid-360s BC, he was taught the 'idealist' doctrine that what we perceive is just a pale reflection of the true reality. After a sharp reaction against Platonism, he achieved inThe Metaphysicsan extraordinary synthesis, integrating the natural and rational aspects of the world. In so doing he probed some of the deepest questions of philosphy: What is existence? How is change possible? What makes something the same thing at different times? Are there things which must exist for anything else to exist at all? The seminal notion of 'substance' and associated concepts of matter and form, essence and accident and potentiality and actuality, have had a profound...