1. Our soul is either a substance or a mode; it is not a substance, because we have already shown that there can be no finite substance; it is therefore a mode.
2. Being a mode then, it must be such either of "substantial" extension or of "substantial" thought; not of extension, because, &c.; therefore of thought.
3. "Substantial" Thought, since it cannot be finite, is infinitely perfect in its kind, and an attribute of God.
4. Perfect thought must have a Knowledge, Idea, or mode of thought of all and everything that is real, of substances as well as of modes, without exception.
5. We say, that is real, because we are not speaking here of a Knowledge, Idea, &c., which completely knows the nature of all things as involved in their essence, apart from their individual existence, but only of the Knowledge, Idea, &c., of the particular things which are constantly coming into existence.
6. This Knowledge, Idea, &c., of each particular thing which happens to be real is, we say, the soul of this particular thing.
7. All and sundry particular things that are real, have become such through motion and rest, and this is true of all the modes of "substantial" extension which we call bodies.
8. The differences among these result solely from the varying proportions of motion and rest, through which this is so, and not so -- this is this, and not that.
9. From such proportion of motion and rest comes also the existence of our body; of which, consequently, no less than of all other things, there must be a Knowledge, an Idea, &c., in the thinking thing, and hence at once also our soul.
10. This body of ours, however, had a different proportion of motion and rest when it was an unborn embryo; and in due course, when we are dead, it will have a different proportion again; none the less there was at that time [before our birth], and there will be then [after death] an idea, knowledge, &c., of our body in the thinking thing, just as there is now; but by no means the same [idea, &c.], since it is now differently proportioned as regards motion and rest.
11. To produce, in "substantial" thought, such an idea, knowledge, mode of thought as ours now is, what is required is, not any body you please (then it would have to be known differently from what it is), but just such a body having this proportion of motion and rest, and no other: for as the body is, so is the Soul, Idea, Knowledge, &c.
12. As soon, then, as a body has and retains this proportion [which our body has], say, e.g., of 1 to 3, then that soul and that body will be like ours now are, being indeed constantly subject to change, but to none so great that it will exceed the limits of 1 to 3; though as much as it changes, so much also does the soul always change.
13. And this change in us, resulting from other bodies acting upon us, cannot take place without the soul, which always changes correspondingly, becoming aware of the change. And [the consciousness of] this change is really what we call feeling.
14. But when other bodies act so violently upon ours that the proportion of motion [to rest] cannot remain 1 to 3, that means death, and the annihilation of the Soul, since this is only an Idea, Knowledge, &c., of this body having this proportion of motion and rest.
15. Still, since it [the soul] is a mode in the thinking substance it could also know, and love this [substance] as well as that of extension, and by uniting with substances (which remain always the same) it could make itself eternal.