Thomas Aquinas, Compendium of Theology

We must go on to demonstrate that God is intelligent. We have already proved that all perfections of all beings whatsoever pre-exist in God superabundantly. Among all the perfections found in beings, intelligence is deemed to possess a special pre-eminence, for the reason that intellectual beings are more powerful than all others. Therefore God must be intelligent.

Moreover, we pointed out above that God is pure act without any admixture of potentiality. On the other hand, matter is being in potency. Consequently God must be utterly free from matter. But freedom from matter is the cause of intellectuality. An indication of this is that material forms are rendered intelligible in act by being abstracted from matter and from material conditions. Therefore God is intelligent.

We proved, further, that God is the first mover. This very perfection appears to be a property of intellect, for the intellect, we observe, uses all other things as instruments, so to speak, in producing movement. Thus man, through his intellect, uses animals and plants and inanimate objects as instruments, of a sort, to cause motion. Consequently God, the first mover, must be intelligent.