SCG, Book I, Chapter 17

ST. THOMAS D'AQUINO: THAT THERE IS NO MATTER IN GOD [Quod in Deo non est materia]

[1] From this [i.e., that there is no passive potency in God, Quod in Deo non est potentia passiva] it is likewise evident that God is not matter [Deum non esse materiam].

[2] Whatever matter is, it is in potency [Quia materia id quod est, in potentia est].

[3] Matter, furthermore, is not a principle of acting [Item. Materia non est agendi principium]. That is why, according to Aristotle, the efficient cause and matter do not coincide [Physics II, 7]. But, as we have said, it belongs to God to be the first efficient cause of things. Therefore, He is not matter.

Aristotle's distinction between efficient causes and the matter upon which they act can be seen this way: since every change matter undergoes must be caused by something, the cause for its alteration cannot be in the matter itself, otherwise one and the same matter would both retain and alter its exact proportions. Hence, only if an efficient cause is distinct from matter can the matter retain its exact characteristics and yet still undergo changes. Matter is that which undergoes change, and therefore it is passive with respect to efficient causes, and indeterminate with respect to formal causes. Matter becomes determinate ("specific") by being informed and, by the same token, becomes active by means of efficient causes, which are themselves ordered toward some end.

[4] Moreover, for those who reduced all things to matter as to the first cause it follows that natural things exist by chance. Aristotle argues against these thinkers in Physics II [8]. Hence, if God, Who is the first cause, is the material cause of things, it follows that all things exist by chance.

The reason a purely material world can only give "chance" explanations for natural phenomena, is that matter [hyle] intrinsically lacks its own determining principles, otherwise efficient and formal causes would be unable to "revoke" matter's principles and produce material variability. Since matter per se lacks intrinsic formal and efficient principles, it is "open" the so to speak mutable determinateness which efficient and formal causes bring to bear upon it. As such, if everything were matter, there would be no intrinsic principles for why each thing is what it is. We could only cite "chance," or, in other words, sheer ignorance. Chance is a code word for ignorance, not a meaningful explanation.

[5] Again, matter does not become the cause of something actual except by being altered and changed [Item. Materia non fit causa alicuius in actu nisi secundum quod alteratur et mutatur]. But if, as we have proved, God is absolutely immobile, He cannot in any way be the cause of things according to the mode of matter.

[6] Now, the Catholic faith professes this truth, namely, it asserts that God has created all things, not out of His own substance, but out of nothing [qua Deum non de sua substantia, sed de nihilo asserit cuncta creasse].

[7] On this point, however, the madness of David of Dinant stands confounded. He dared to assert that God is the same as prime matter on the ground that, if He were not, He would have to differ from it by some differences, and thus they would not be simple. For in the being that differs from another by a difference, the difference itself produces a composition. David’s position was the result of ignorance. He did not know how to distinguish between difference and diversity […qua nescivit quid inter differentiam et diversitatem intersit]. The different, as is determined in Metaphysics X [3], is said relationally [ad aliquid], for every different is different by something [omne differens aliquo est differens]. Something is called diverse, however, absolutely, from the fact that it is not the same [diversum autem aliquid absolute dicitur, ex hoc quod non est idem]. Difference, therefore, must be sought among those things that agree in something, for we must point to something in them according to which they differ: for example, two species agree in genus and must therefore be distinguished by differences. But in things that agree in nothing we need not seek the whereby they differ; they are diverse by themselves [In his autem quae in nullo conveniunt, non est quaerendum quo differant, sed seipsis diversa sunt]. In the same way, opposite differences are distinguished from one another [Sic enim et oppositae differentiae ab invicem distinguuntur]. For they do not share in the genus as a part of their essence, and therefore, since they are by themselves diverse, there is no need to seek that by which they differ [et ideo non est quaerendum quibus differant, seipsis enim diversa sunt]. In this way, too, God and prime matter are distinguished: one is pure act, the other is pure potency, and they agree in nothing [Sic etiam Deus et materia prima distinguuntur, quorum unus est actus purus, aliud potentia pura, in nullo convenientiam habentes].