The relation of soul to body is like that of form to matter (or shape to wax), not like two things accidentally joined; hence asking whether soul and body are 'one' is a confused question.

By Aristotle, from On the Soul

Key Arguments

  • Immediately after defining soul as actuality of a natural instrumental body, he says: 'That is why we should not inquire whether the soul and the body are one, any more than the wax and the shape, or, in general, the matter of a given thing and that of which it is the matter.'
  • He invokes his general doctrine that 'one and being are said of things in many ways, the controlling way is actuality', implying that soul–body unity is to be understood via the unity of an actualized composite, not as a union of two independent substances.
  • By comparing soul–body to 'the wax and the shape', he illustrates that the form (e.g., shape) is not a separate object alongside the matter (wax) but the way in which the matter is, so it is misguided to ask whether they are 'one' in the way two objects might be.
  • This supports his broader hylomorphic claim that psychological questions must be framed in terms of form–matter composites rather than Cartesian-style unions of two distinct substances.

Source Quotes

{22} If, then, we must state something that is common to every soul, it would be that it is the first actualization of a natural instrumental | 412 b 5 | body. That is why we should not inquire whether the soul and the body are one, any more than the wax and the shape, or, in general, the matter of a given thing and that of which it is the matter. 149 For, since one and being are said of things in many ways, the controlling way is actuality.
That is why we should not inquire whether the soul and the body are one, any more than the wax and the shape, or, in general, the matter of a given thing and that of which it is the matter. 149 For, since one and being are said of things in many ways, the controlling way is actuality. 150 It has now been stated in universal terms what the soul is.

Key Concepts

  • That is why we should not inquire whether the soul and the body are one, any more than the wax and the shape, or, in general, the matter of a given thing and that of which it is the matter.
  • For, since one and being are said of things in many ways, the controlling way is actuality.

Context

II.1 (412b5–9), where Aristotle draws an immediate methodological consequence from his hylomorphic definition, warning against misconceived questions about the unity of soul and body.