Assuming there is an intellect, we're clearly not this universal intellect or we would know it. So that's one function of soul.

For Plotinus, what really exists are the Platonic forms, so the true nature or form of things like justice, beauty, maybe numbers, things like that, and these he associates with the intellect because they're the objects of intellect, they are things that intellect can think about.

There's going to be this realm of Platonic forms and then there's going to be this single mind, the 'nous', which grasps them.

In fact one of the things about Plotinus is that he maybe not singlehandedly, but I think more than anyone else, killed off the variety and dissension among the philosophical schools of antiquity.

The soul is the principle of life, and it's also something much closer to our own awareness and consciousness of our existence because fundamentally for Plotinus what we are is souls, we're not intellects.

Once you're in a kind of revealed religious tradition, you wind up having to explain how the things said about God in the Bible or the Qur'an or whatever religious text you're dealing with, why these statements are true.

The soul must be distinct from intellect because even at its best, what the soul does when it's thinking, is it thinks linguistically, it thinks in a temporarily extended way, so it for example, might go through the steps of an argument chain, as if you were going through a syllogism and seeing that something followed from the premises, whereas intellect simply grasps the forms.