Most Thomist are Catholics(and some confessional protestants) that try to affirm the Nicene Creed but that leaves a tension in their doctrines. On the one hand, they are committed to a radical form of simplicity. On the other hand, they maintain distinctions in the Trinity(the persons). How do Thomist reconcile these issues? They do so by appealing to the notion that the persons are subsistent relations. Whatever that is there still lies the question about what relation do these relations play to the essence. In an exchange with a Catholic these comments were made:

Thomasinos said:

Solitary bean said:

Wouldn’t that mean that the divine, simple essence engages in real relations? If so, wouldn’t relations be characteristic of complex things? I’d think any supposed relations would only be conceptual.
So God’s relations are intra to the divine essence not extrinsic, and these relations proceed logically but are differentiated conceptually? (Readinig ST I.28.I-II.)

The relation signified by the term “the same” is a logical relation only, if in regard to absolutely the same thing; because such a relation can exist only in a certain order observed by reason as regards the order of anything to itself, according to some two aspects thereof. The case is otherwise, however, when things are called the same, not numerically, but generically or specifically. Thus Boethius likens the divine relations to a relation of identity, not in every respect, but only as regards the fact that the substance is not diversified by these relations, as neither is it by relation of identity.

I think we’d need an explanation of how you can have a quasi-identity relation that doesn’t multiply the substance but does multiply the persons.

Necessitarian said:

There is confusion about what “essence” tells us in Thomasinos formulation. If the essence is just God’s nature qua God (viz. His perfections, His Godhead), then we might end up in vacuity. It depends on how we spell this out. Thomas could be saying that there are no real distinctions in the essence. If so, whence comes relations of this essence to itself? If the relations of the essence (to itself) just constitute (something of) the essence, then you have distinctions in the essence (the Father vs the Son). If the relations of the essence (to itself) are external, then you have complicit unitarianism, where the Trinity emanates or otherwise ontologically derives from an abstract divine-substance. Now, Thomas could simply mean that the Trinity is just part of God’s nature, like omnipotence and infinity, so that to talk about God’s perfections and leave out the Trinity is as incoherent as eschewing God’s aseity, omnipotence, or infinity. Fair enough – I think that’s true. But it’s completely beside the point of EG and Trinitarian relations.