Substance
means (a) simple bodies, e.g. earth, fire, water and the like; and in general bodies, and the things, animal or divine, including their parts, which are composed of bodies. All these are called substances because they are not predicated of any substrate, but other things are predicated of them.
(b) In another sense, whatever, being immanent in such things as are not predicated of a substrate, is the cause of their being; as, e.g., the soul is the cause of being for the animal.
(c) All parts immanent in things which define and indicate their individuality, and whose destruction causes the destruction of the whole; as, e.g., the plane is essential to the body (as some Footnote 1The Pythagoreans and Platonists. hold) and the line to the plane. And number in general is thought by some Footnote 2The Pythagoreans and Platonists. to be of this nature, on the ground that if it is abolished nothing exists, and that it determines everything.
(d) Again, the essence , whose formula is the definition, is also called the substance of each particular thing.
Thus it follows that substance
has two senses: the ultimate subject, which cannot be further predicated of something else; and whatever has an individual and separate existence. The shape and form of each particular thing is of this nature.