The word "metaphysics" originally was the title (Greek, meta ta physika) given by Andronicus of Rhodes (c. 70 B.C.) to the group of the writings of Aristotle (384-322 B.C.) that came after (meta) his writings on physics in his collected writings. It came to mean what Aristotle called First Philosophy (Greek, prote philosophia). Traditionally it has been defined as "the science of being as such," and is the equivalent of ontology. The term "science" here is used in the classic sense of "knowledge" in contrast to "opinion." Sometimes the term "metaphysics" is used in a non-philosophical way to mean anything "beyond the physical," as in "metaphysical healing," "metaphysical poetry," etc. Thus it means any explanation that goes beyond and transcends inadequate or inaccurate ordinary thought. The term will not be used here in this latter sense, but in the traditional sense of the "science of being" answering the question: "What is reality?"

To the question "What is reality?" philosophers have given different answers; these answers often fall into one of the following views:

1. Idealism - reality is mind or like mind, thought or consciousness. Since reality cannot be understood without reference to the activity of the mind, reality must be of the nature of mind.

2. Materialism - reality is matter or energy. All things and events, including life, consciousness, and mind, are most adequately explained in terms of states of matter or energy.

3. Naturalism - nature is real; mind and matter both arise from nature and nature is the ultimate source of both mind and matter. There is no supernatural source of these beyond nature.

4. Theism - ultimate reality is beyond nature and this supernatural reality, called God, is the source of nature, both mind and matter.