Aquinas on Incarnation as a rock or animal

Aquinas thinks it would be unfitting for God to become incarnate as a non-rational creature. In Summa Theologiae III.4.1, his reasoning is that human nature had an appropriate dignity, as it “was apt to contain the Word Himself in some way through its operation, by knowing Him and loving Him”, but not so for the non-rational creatures. In Summa Contra Gentiles 4.55 we have a different and more philosophical argument:

We must also observe that the rational creature alone acts of itself, for irrational creatures are more driven by natural impetus than act of themselves [magis aguntur naturali impetu quam agant per seipsas]; thus they are to be regarded as instruments rather than principal agents. Now it was fitting that God should assume a creature capable of acting of itself as principal agent, because an instrumental agent acts through being moved to action, whereas the principal agent acts itself and of itself. Accordingly, if God were to do anything by means of an irrational creature, all that is required in accordance with that creature’s natural condition is that it be moved by God, and there is no need for it to be assumed into personal union so as to act itself, since its natural condition does not admit this, it being admitted solely by the condition of rational nature [quia hoc eius naturalis conditio non recepit, sed solum conditio rationalis naturae]. (Shapcote, with italicized phrases retranslated.)

In neither text does Thomas deny the metaphysical possibility of God being incarnate as a nonrational creature, such as a rock, plant or animal. While this is an argument from silence, I think it is a pretty strong one: if he thought it was impossible, we really would expect him to say so, rather than merely saying it was unfitting.

Both arguments seem to me to be based on the idea that if it’s fitting for God becomes incarnate as X, if there is to be much of a point to this incarnation, this X needs to be of a sort that can express the divine person in a special way. If the Logos were to become a piece of granite, the petrous behavior of the rock would not differ from that of any other piece of granite. But if the Logos becomes a human, the rational behavior of this human is able to distinctively express the Logos in a way that ordinary human persons do not. We see this in the Gospels: Jesus as a human being, in his free human choices, movingly expresses the personality of the Second Person of the Trinity. He is just as human as all of us, but all of us humans are different from one another in our operations in a way that is expressive of the person. Of course, all pieces of granite are different from another, but these differences are not due to the operations of the rock differently expressing the rock’s hypostasis (we shouldn’t say person!). Rather they are due to the differences in the matter the rock was formed from and the external forces. God can be expressed in granite.

Of course, every rock reflects God’s goodness, and some rocks especially so, say because they are formed into a beautiful statue or inscribed with a meaningful text. But the special expression of God’s goodness is just a function of the rock’s initial matter and external influences. If God wants a rock to particularly well express him, there is no advantage to God’s becoming the rock: “all that is required … is that it be moved by God”—and all rocks are ultimately moved by God. But it is different for a human, that is a self-originator of its behavior. For the self-originated agency to be fully an expression of God, the person who is human, from whom that behavior originates, needs to be a person who is God. There is thus something that the Logos can accomplish by taking on a rational nature that cannot be accomplished in any other way. We might say that all of creation is God’s self-expression by creatures, but in becoming a human, God can be self-expressed in a creature—something that could not happen if God were to become a non-rational creature. This highlights how it it is that the Incarnation is also an ultimate completion of the act of creation. God’s becoming a non-rational creature would be just God showing off, rather than God manifesting his love by living that love as a human.

TWo closing thoughts. First, I think Aquinas’ Contra Gentiles argument works best if non-rational creatures function deterministically. Given quantum mechanics, we have good reason to think they are indeterministic. But nonetheless the basic point remains: randomness is not really a self-expression, so even if the Logos were to control the quantum processes from the inside, it seems that as long as that control was fully in accordance with the nature of the non-rational creature, it wouldn’t be distinctively expressive of divinity.

Second, I am not sure that Aquinas’ Contra Gentiles argument fits well with Aquinas’ theological compatibilism, on which God can through primary causation make us freely behave a particular way. At least we can say that the argument works better if we have theological indeterminism. And thus theological indeterminism has a theological advantage: it gives us a deep reason for why the incarnation as a human is fitting.