In fact Plotinus thought not only that soul in general is eternal so that you always have soul, but he thought that each person's soul is eternal.

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.

Just the way you might look at a painting and see the painting, and the painting is outside you, so this immaterial intellect would see the forms and behold them, as if they were standing before it. And Plotinus said that that can't be right because it falls prey to sceptical objections.

In fact Plotinus thought not only that soul in general is eternal so that you always have soul, but he thought that each person's soul is eternal.

There's a stronger and more kind of controversial element of Plotinus' view of matter, which is that he actually identifies it with evil, or at least the principle of evil, and the reason for this is that he thinks that the the One, the highest principle, can also be thought of as the Good, and that's kind of surprising like, because he has this negative theology which doesn't allow us to say anything about the One. But he believes that it can be seen as the principle of goodness as well as unity, and that if you think about it, goodness and unity sort of go along with each other.

The intellect must be different from the soul.

The importance of Plotinus is not only his own philosophical ideas which are quite interesting, but his historical impact as the founder of neo-Platonism which is the main philosophical tradition of late antiquity.