Note: A friend in college emailed me and asked for help on some technical questions related to soul and free will. Here is my answer to her, since they are salient issues – may help others.
Your first question: Aristotle argues that the human person is fundamentally a composite union of body and soul; Plato argues that the human person is fundamentally the soul only. Which philosopher do you think is right, why, and why does this matter?
Plato saw the soul as immaterial and eternal [and basically personal], whereas Aristotle tied the soul to body as some life force [potentially collective if not tied to body, body makes it personal].
Why does this question matter? Related to the social direction, a consequence for society would be how we view the human person, and affect social help. If the body is a real expression of the person, then we [as Christians] must also be called to improving the physical conditions of others as we can. Does that make sense?
I think the best way to frame it is to say that we have ‘free will’ within the parameters of sovereignty [grace]. Or, we are commanded to use our wills, and will answer for that usage, but if we exercise our wills against sovereignty, at some point we destroy ourselves from existence.
[God] in no way wills the evil of sin, which is the privation of right order towards the divine good. The evil of natural defect, or of punishment, he does will, by willing the good to which such evils are attached. Thus in willing justice he wills punishment; and in willing the preservation of the natural order, He wills some things to be naturally corrupted... 
The statements that evil exists, and that evil exists not, are opposed as contradictories; yet the statements that anyone who wills evil to exist and that he wills it not to be, are not so opposed; since either is affirmative. God therefore neither wills evil to be done, nor wills it not to be done, but wills to permit evil to be done; and this is a good. 
Punishment is a function of the good to which evils are attached, not a function of prior divine imperative. God cannot will the sinner to evil, since this is a “privation of right order towards the divine good.” God can will a context in which the sinner chooses evil, but this is only because God has first willed the attendant good. The sinner wills evil, and God wills punishment, or justice, which is a good.
 Aquinas, ST, I 19.10.