Divine Relationality and Temporality

Derek, a commentator on my blog, has asked me some about whether essential divine relationality (as implied in the Christian doctrine of the Trinity) entails essential divine temporality. In other words, would God's being essentially an active, loving, multi-personal unity require that God experience continued change and hence divine temporality?

In response, I submit "no" as the correct answer. My reasoning is as follows:

First, I assume that time requires change. No change; no time. That is a controversial assumption (It has been questioned, for example, by Sidney Shoemaker and W.H. Newton-Smith.), but I think it's right. If so, then divine temporality requires divine change, and essential divine temporality requires essential divine change.

Second, I assume that creation is a free (i.e., unnecessary) act on God's part. Hence, it is not essential to God that he be a creator.

Third, I assume that whatever is not God or part of God, is created by God. It follows that any essential divine change has to be purely internal to God.

Fourth, and crucially, I don't see how there could be change internal to God independent of his decisions vis-a-vis creation. Suppose that God is a tri-personal society of Father, Son, and Holy Spirit essentially loving each other. For this internal divine relationality to imply divine temporality requires either that one of the relata (Father, Son, or Holy Spirit) changes, or that one of the relations (F-S, S-HS, F-HS, F-S-HS) changes. But if God is essentially a Trinity of F-S-HS, then the relations are fixed (unless, somehow, the relata could, say, swap places - but is that coherent?), so any purely internal change in God would have to be a change in the relata.

How, then, could the relata change? Could the Father change in knowledge of the Son or Holy Spirit? Given God's essential omniscience, the answer must be no, unless the members of the Trinity could change in some other respect. And what would that be? Could the Father change in will for the Son or Holy Spirit? It is hard to see how. If the Father is perfectly loving and essentially omniscient, then he necessarily knows and wills the true good of the others, and it is not at all clear why their true good would change. Nor is it clear how there could be any new way for the Father to express love for the Son, or vice-versa. After all, if the intra-Trinitarian love is infinite and perfect, then how could it fail to be fully expressed? And if, necessarily, it is fully expressed, then there is nothing more that Father, Son, or Holy Spirit could do merely with respect to each other?

I have no problem understanding how God could change in relation to creation, in particular to libertarianly free creatures, nor do I have a problem with God's changing in himself by making a free decision to create or not to create. Nor do I have a problem with the intra-Trinitarian relationship changing on account of differential responses on the part of Father, Son, and Holy Spirit to a changing creation. But all of those types of changes concern creation and not just intra-Trinitarian relationality.

So I guess I'm just not sure what it would look like for God to be changing purely in virtue of being a Trinity. Perhaps Derek or someone else can help me out with that one.