That branch of philosophy that studies the most general categories and concepts presupposed in descriptions of ourselves and the world. Examples are causality, substance, ontology , time , and reality. Metaphysical questions have a very broad scope. Whereas the chemist might investigate particular substances, the metaphysician asks what it means to be a substance, and whether there is one basic substance, or many.
Metaphysical questions can become the subject of more specialized philosophical inquiry.
We can ask whether our actions are subject to causality, which gives rise to the problem of free will . And the question of whether our mental experiences involve a separate substance from body is a major issue in the philosophy of mind. Although metaphysics dates back to the ancient Greeks, there have been occasions on which its status as a legitimate inquiry have been questioned. The rise of science in the 17th century led to attempts by some philosophers, such as Hume and Locke, to limit the claims of metaphysics, and earlier this century scientifically minded philosophers, such as the logical positivists, claimed that metaphysical assertions were meaningless. The Macmillan Encyclopedia 2001 2.