one is the indivisible atom. In this sense, a body is not a substance, and whether it is composed of such atoms is disputed.

The second meaning:

That which occupies space. In this sense, a body is a substance. Those who deny the indivisible atom say that every body is a substance and every substance is a body, while those who affirm it say that substance is broader than body.

The third meaning:

Intelligible substances, according to those who affirm substances that do not occupy space, such as intellects, souls, matter, and forms. These Peripatetic philosophers claim that substance falls into five categories.

Most rational people reject this and say:

“These things you have called intelligible substances exist only in the mind, not in external reality.”

“Substances” may also mean things that subsist in themselves. For those who understand substance to be broader than body, negating the broader category also negates the narrower. The same applies to those who regard substance as synonymous with body. But for those whose understanding of substance does not encompass body—for example, supposing that they use the term “substance” only for the indivisible atom—denying that He is a substance does not entail denying that He is a body, except through the argument he mentioned, namely:

“A body is composed of substances.”

Thus, the argument is valid only on the assumption that this terminological convention is established, although I know of no one who adopts it without qualification,