within it an intellectual composition that has no existence in concrete reality. They claim that a species is composed of genus and differentia. Thus, if you say:

“A human being is a rational animal,”

they respond:

“A human being is composed of these two,”

whereas the human being is merely described by both.

These thinkers then disagreed (1) concerning body: Is it composed of indivisible parts, each being what they call an indivisible atom—a thing no one has ever perceived with the senses and which, according to those who affirm it, is smaller than anything we might conceive? Or is it composed of matter and form as an intellectual composition?

When their account of matter is subjected to close scrutiny, nothing is found except the body itself and its accidents. Sometimes “matter” means the body, which is a substance, while “form” means its shape and the continuity inhering in it. At other times, “form” means the body itself (2), which is the substance, while “matter” means magnitude in the abstract, common to all bodies; or it means that from which the body (3) was created.

“Form” may also refer to an accidental property (4), namely the continuity and shape inhering in the body. Thus, the body is that which is continuous, while form is (5) the continuity itself. Form here is therefore an accident, while matter is the body, as with an artificial form (6): the shape of a bed is its form (7), while the wood is its matter.