For the definition of soul as a blend or harmony of physical qualities, or a self-moving number…
For Aristotle’s rejection of Plato’s description of the soul as a self-mover…
Plato describes the soul in Timaeus 34B-36D as composed out of divisible and indivisible forms of Sameness, Difference and Being. These are in turn split into two oppositely revolving circles of Sameness and Difference. Interpretations are offered in Plutarch On the Creation of Soul in the Timaeus (Moralia 1012A-1032F) and in the commentaries on the Timaeus of Proclus and Calcidius. See for a ‘yes and no’ answer to the question whether all soul is one, which tries to trade on the soul’s being composed of the divisible and the indivisible and of Sameness and Difference.
Aristotle, taking the apparently spatial character of Plato’s account literally, rejects it utterly and substitutes a highly commonsensical account. His general formula, that the soul is the form or actualisation (entelekheia) of an organic body (DA 2.1, 412a19 and b5), he recognises as being a very generalised sketch, which can be filled in by studying the life-manifesting capacities one by one (2.3, 414b25-8; b32-3; 415a12-13). The soul, for Aristotle, actually is these capacities, as I have argued (1974). The capacities which constitute soul are first the nutritive capacity for using food to maintain and reproduce a certain bodily structure, secondly in higher life forms, the further capacities to perceive and desire, and thirdly in humans the capacity to think. (SorabjiPC1:245)