Dodds calls the next section of the Elements of Theology, consisting of propositions XL through LI, "Of the Self-Constituted." I very tentatively disagree with his sectioning: the last two propositions of this section seem to me to be better suited in the next (concerning time). But that's a problem for another day: twelve propositions is too much to tackle at once anyway and so we'll start with the first few for now. (Even these were too much!) Here, Proclus introduces the concept of self-constitution and shows that incorporeals are self-constituted.
On Self-Constitution: We will call independent things "self-constituted." Intellect is essentially self-constituted, and souls are lent self-constitution by their participation in intellect.
XL. The Good is better than self-constituted (e.g. independent) things; self-constituted things are better than dependent things.
The Good is not self-constituted, since the Good is the One [XIII], and if the One caused itself it would be not-One [II], which is a contradiction.
Suppose nothing below the Good was self-constituted. But then there would be nothing independent, because the Good is not independent [X] and we have supposed everything else to be dependent. But with nothing independent, there would be nothing to mediate between the dependent and the Good [IX], and so nothing but the Good would exist, which is obviously incorrect.
So something below the Good must be self-constituted, and it must be those which are immediately below the Good, since the Good depends on nothing [XII] and produces things as like itself as possible [XXVIII], and being independent is better than being dependent [IX]. Therefore self-constituted things are better than dependent things.
XLI. Every thing that exists in some other thing is caused by that other thing; every thing that exists in itself is self-constituted.
When we say "exists in," we means "depends on as a cause." So if something exists in something else, it is caused by it, and it cannot be self-constituted. But if something exists in itself, it is caused by itself, therefore independent, therefore self-constituted.
XLII. Every self-constituted thing is capable of returning to itself.
Every thing that proceeds from a cause returns to it [XXXI], so if a thing causes itself, it will return to itself.
XLIII. Every thing capable of returning to itself is self-constituted.
It is the nature of every thing to return to its cause [XXXIV], so if a thing returns to itself, it must be its own cause.
XLIV. Every thing capable of returning to itself in activity (e.g. is self-directed) is capable of returning to itself essentially (e.g. is self-constituted).
Suppose that a thing can return to itself in activity but not in existence. Since every independent thing is better than every dependent thing [IX], the thing's activity is better than its existence. But this is impossible, since a thing must exist before it can act, and so its existence must be better than its action. So if a thing is capable of returning to itself, its essence is inherently independent.
This section really kicked my ass! Why does Proclus introduce a new concept ("self-constitution"), only to immediately prove it the same as as an old concept (capability of self-direction)? Why does Proclus equate self-constitution (and therefore capability of self-direction) with independence (e.g. self-causation), when he has already proved the existence of counter-examples (e.g. soul is capable of self-direction but is externally-caused, see XX)? Why does Proclus seem to demonstrate the same thing repeatedly (IX and X vs. XL, XLII and XLIII vs. XLIV)? In the end, I didn't manage to make heads or tails of it and had to give up.
I was opining to my angel about all this, and They said, "Remember, the trying to understand is more important than the understanding." They're right, of course: the point here is growth, and growth comes from making the effort, so we'll just have to proceed as best we can! The good news is that I started studying Proclus in the hopes that he would fill in the gaps in my understanding of Plotinus. And he is, in a round-about sense: he agrees in the main but disagrees in all the details—literally almost all of them!—and in trying to understand those details, I'm having to go over Plotinus and Porphyry again with great care. So the gaps are, slowly, getting filled in... I suppose I'm just frustrated, and I wish it was easier, but that's not how it works.
As far as I can tell, Proclus' proofs rely on self-constitution being the same as independence (introduced way back in IX), so despite his use of the new term, I simply treat it as a synonym. (Dodds seems to suggest that this is an error and the new term is used for a reason, but most of his commentary is in Greek and unreadable to the likes of me. Evidently self-constitution is related to free will, but then I don't see how it can be equated with ontological self-causation as Proclus has previously defined it.) Either way, though, it seems to me that there are a number of glaring contradictions now present in Proclus' model, and I'm unfortunately unsure where those originate: is it me? is it our translators? is it the manuscript copyists? is it Proclus? is it Proclus' antecedents? Maybe things will fall into place later on as we see how these propositions and concepts get used.