The Soul is not a Mixture: it has free Choices.

It is, therefore, clear to any one who has knowledge that Weights and Constituents of Good and Evil neither outweigh one another, nor are outweighed by one another ; but on the contrary, there are real free Choices which conquer one another and are conquered by one another, since all the Choices can become one Choice. For if good Choices spring up in us from the good Root which is in us, and evil Choices are produced in us from that evil Root which is in us, then these (powers) in us are not independent free Choices, but Natures fixed by Necessity.