Key Arguments

• He begins from his general ontology: 'one kind (genos) among the beings is substance, and of this, one sort is substance as matter... and another is shape and form... and a third, what is composed of these', and identifies matter with potentiality and form with actuality.
• He classifies natural bodies into those that have life and those that do not, adding: 'by life we mean self-nourishment, growth, and decay', so any natural body with these capacities is a substance, but 'a substance as a composite'.
• He argues that since the living body is 'also a body of such-and-such a sort, for it has life, it would not be a body' in the sense of a mere substrate; 'the body is not among the things that are predicated of an underlying subject, but rather [is spoken of] as an underlying subject and matter', so what makes it a living body must be its form.
• From this he infers: 'It is necessary, then, for the soul to be substance as form of a natural body that has life potentially. | 412 a 20 | But substance is actuality. Therefore, it is the actualization of such a body.'
• He then specifies which kind of actuality the soul is by using the distinction between actuality as scientific knowledge and as contemplating: 'And it is evident that it is as scientific knowledge is', because sleep/waking show that life can be present without being exercised.
• He concludes and restates: 'That is why the soul is the first actualization of a natural body that has life potentially.'

Source Quotes

II 1 So much, then, for the views handed down by our predecessors concerning the soul. | 412 a 1 | Let us go back again and start afresh, as it were, and try to determine what the soul is and what its most common account would be. 141 | 412 a 5 | We say, then, that one kind (genos) among the beings is substance, and of this, one sort is substance as matter, which is intrinsically not a this something, and another is shape and form, on the basis of which something is already said to be a this something, and a third, what is composed of these. 142 And matter is potentiality, whereas form is actuality—and this in two ways, as scientific knowledge is | 412 a 10 | and as contemplating is.

141 | 412 a 5 | We say, then, that one kind (genos) among the beings is substance, and of this, one sort is substance as matter, which is intrinsically not a this something, and another is shape and form, on the basis of which something is already said to be a this something, and a third, what is composed of these. 142 And matter is potentiality, whereas form is actuality—and this in two ways, as scientific knowledge is | 412 a 10 | and as contemplating is. 143 It is bodies that seem most of all to be substances, and among these, the natural ones.

144 For these are starting-points for the others. 145 Of natural bodies, some have life, while some do not have it. And by life we mean self-nourishment, growth, and decay. So every natural body that participates in life would be a substance, | 412 a 15 | but a substance as a composite.

And by life we mean self-nourishment, growth, and decay. So every natural body that participates in life would be a substance, | 412 a 15 | but a substance as a composite. But since it is also a body of such-and-such a sort, for it has life, it would not be a body.

For the body is not among the things that are predicated of an underlying subject, but rather [is spoken of] as an underlying subject and matter. It is necessary, then, for the soul to be substance as form of a natural body that has life potentially. | 412 a 20 | But substance is actuality. 146 Therefore, it is the actualization of such a body. But something is said to be actual in two ways, either as scientific knowledge is or as contemplating is.

For both sleep and waking depend on the presence of the soul; waking is analogous to contemplating, and sleep to | 412 a 25 | having but not actualizing [scientific knowledge]; and in the same individual scientific knowledge is prior in coming to be. 147 That is why the soul is the first actualization of a natural body that has life potentially. This sort of body would be one that is instrumental.

Key Concepts

• We say, then, that one kind (genos) among the beings is substance, and of this, one sort is substance as matter, which is intrinsically not a this something, and another is shape and form, on the basis of which something is already said to be a this something, and a third, what is composed of these.
• And matter is potentiality, whereas form is actuality—and this in two ways, as scientific knowledge is | 412 a 10 | and as contemplating is.
• Of natural bodies, some have life, while some do not have it. And by life we mean self-nourishment, growth, and decay.
• So every natural body that participates in life would be a substance, | 412 a 15 | but a substance as a composite.
• It is necessary, then, for the soul to be substance as form of a natural body that has life potentially. | 412 a 20 | But substance is actuality. 146 Therefore, it is the actualization of such a body.
• That is why the soul is the first actualization of a natural body that has life potentially.

Context

Opening of II.1 (412a1–23), where Aristotle turns from reviewing predecessors to his own positive, generic definition of the soul using his hylomorphic ontology of matter, form, potentiality, and actuality.