METAPHYSICS (from Gr. Meta to 'ha sika, °after physics," alluding to the position of Aristotle's treatise on metaphysics in his works). Metaphysics and epistemology (q.v.) are the twin sciences of the nature of reality and of our knowledge thereof. Metaphysics seeks for the criteria of being, epistemology for those of truth. As the truth is generally conceded to possess some peculiarly intimate relation to reality which is not found in the case of error, and as our sole avenues of access to reality are those of experience, be it sensory, rational, emotional or volitional, the boundary line between epistemological and metaphysical opinions is of the most obscure and wavering nature, so that a separate study of the two dis ciplines is exceedingly unprofitable. We shall accordingly shift our standpoint continually from that of one science to that of the other.
Metaphysics is nbt a subject which one can study or refuse to study at will; whether it is explicit or not, there is always some criterion of truth, of reality, that permeates our barest common sense. This may be metaphysically inadequate, but must be metaphysical. When I draw a distinction between a dream and an experience of waking life, between a truth and a lie, between a fact and an error, I am draw ing a metaphysical distinction. When a physi cist reduces the table before him to a vast aggregate of electric charges, or asserts the basic identity of time and space, or interprets light a transverse electromagnetic vibration, he is nothing if not metaphysical, for he is drawing a distinction between the appearance of things and their underlying reality. Even those who claim to be agnostics or sceptics in the pro fessor's chair are tainted with metaphysics in their daily life, for the only agnosticism, the only scepticism which can free itself from all blemish of metaphysics is an agnosticism, a scepticism so complete that it does not even tentatively maintain any criterion of reality or unreality, of truth or falsity.
We have accordingly three stages of meta physics to discuss: (1) the metaphysics of com mon sense; (2) the metaphysics of the natural scientist; (3) the metaphysics of the technically trained philosopher.
(1) The Metaphysics of Common Sense. — The average philosophical layman, be he edu cated or not, believes that the wall he sees in front of him, the cane that he holds, the song that he hears are real, with an immediate and underived reality. He is confident that the wall, the cane, even the song would be the same with nobody to experience them. He is also confi dent that he exists, and that his existence is utterly independent of any experience he may have. Now, this view that the object is out there and I am in here, and that seeing is something which needs no analysis (for so the layman believes), works remarkably well pro viding I only see things that are so. It is, however, clear that in my dreams and other illusions I frequently see things that in some manner are not so. If seeing is an immediate relation between me and my object, what is my object when I dream of something which, in every common-sense interpretation of the words, does not exist? This is obviously the highest common factor of metaphysics and epistemology, for it unites the fundamental questions of the two sciences, the question of truth and that of reality. What is more, it is in essence the one cardinal prob lem of both sciences, the great problem of error. The problem of error may be ap proached from two different angles, according as there are supposed to be real entities which form the objects of erroneous experience, or no such entities at all. In the latter case, ex perience must be interpreted as not essentially a subject-object relation. As we shall see, practically all the earlier modern philosophers hold that erroneous experiences have objects. The second alternative is indicated in Spinoza and appears in the philosophies of Kant and Hegel.