ST THOMAS D'AQUINO: THAT NO ACCIDENT IS FOUND IN GOD
(Quod in Deo non est accidens)
SCG, I, xxiii
 It follows necessarily from this truth [i.e. that God's being is His own essence and His essence is His own being] that nothing can come to God beyond His essence, nor can there be anything in Him in an accidental way [Deo supra eius essentiam nihil supervenire possit, neque aliquid ei accidentaliter inesse].
 For being cannot participate in anything that is not of its essence [Ipsum enim esse non potest participare aliquid quod non sit de essentia sua], although that which is can participate in something. The reason is that nothing is more formal or more simple than being, which thus participates in nothing [Nihil enim est formalius aut simplicius quam esse. Et sic ipsum esse nihil participare potest]. But the divine substance is being itself, and therefore has nothing that is not of its substance [Divina autem substantia est ipsum esse. Ergo nihil habet quod non sit de sua substantia]. Hence, no accident can reside in it.
 Furthermore, what is present in a thing accidentally has a cause of its presence [Omne quod inest alicui accidentaliter, habet causam quare insit], since it is outside the essence of the thing in which it is found. If, then, something is found in God accidentally, this must be through some cause. Now, the cause of the accident is either the divine essence itself or something else. If something else, it must act on the divine essence, since nothing will cause the introduction of some form, substantial or accidental, in some receiving subject except by acting on it in some way. For to act is nothing other than to make something actual, which takes place through a form [nihil enim inducit aliquam formam, vel substantialem vel accidentalem, in aliquo recipiente, nisi aliquo modo agendo in ipsum; eo quod agere nihil aliud est quam facere aliquid actu, quod quidem est per formam]. Thus, God will suffer and receive the action of some cause--which is contrary to what we already established. On the other hand, let us suppose that the divine substance is the cause of the accident inhering in it. Now it is impossible that it be, as receiving it, the cause of the accident, for then one and the same thing would make itself to be actual in the same respect. Therefore, if there is an accident in God, it will be according to different respects that He receives and causes that accident, just as bodily things receive their accidents through the nature of their matter and cause them through their form. Thus, God will be composite. ...
 Every subject of an accident ... is related to it as potency to act, since the accident is a certain form making the subject to be actual according to an accidental being [Omne subiectum accidentis comparatur ad ipsum ut potentia ad actum: eo quod accidens quaedam forma est faciens esse actu secundum esse accidentale]. But, as we have shown above, there is no potentiality in God. There can, therefore, be no accident in Him.
 Then, too, when a being has an accident inhering in it, it is in some way mutable according to its nature, since an accident can inhere or not-inhere [Cuicumque inest aliquid accidentaliter, est aliquo modo secundum suam naturam mutabile: accidens enim de se natum est inesse et non inesse]. If, then, God has something belonging to Him in an accidental way, He will consequently be mutable. ...
 Again, that which has an accident inhering in it is not whatever it has in itself, since an accident is not part of the essence of the subject. But God is what He has in Himself. There is, therefore, no accident in God [quia accidens non est de essentia subiecti. Sed Deus est quidquid in se habet. In Deo igitur nullum est accidens]. The minor proposition is proved thus. Everything is found in a more noble way in the cause than in an effect. But God is the cause of all things. Hence, whatever is in Him is there in the most noble way [Unumquodque nobilius invenitur in causa quam in effectu. Deus autem est omnium causa. Ergo quidquid est in eo, nobilissimo modo in eo invenitur]. Now, what a thing itself is, this belongs to it in a most perfect way. For this is some thing more perfectly one than when something is joined to something else substantially as form to matter; just as substantial union is more perfect than when something inheres in something else as an accident. God, then, is whatever He has [Relinquitur ergo quod Deus sit quidquid habet].
An annotated, abridged edition of SCG metaphorically explains God's causal eminence by saying, "Shakespeare's genius was a better thing than Shakespeare's Othello."
 It is also a fact that a substance does not depend on an accident, although an accident depends on a substance [Substantia non dependet ab accidente: quamvis accidens dependeat a substantia]. But what does not depend on something can sometimes be found without it. Some substance, then, can be found without an accident. This seems especially to fit the substance that is most simple, such as the divine substance is. The divine substance, therefore, has no accidents whatever.
 In dealing with this problem, Catholics likewise give assent to this opinion. Whence Augustine says in his De Trinitate [V, 4] that “there is no accident in God.”
 The proof of this truth serves as a refutation of the error of some Saracen [i.e. Muslim] theologians “who posit certain intentions superadded to the divine essence" [qui ponunt quasdam intentiones divinae essentiae superadditas].
The online annotated edition explains: "Intentiones. For intentio meaning idea, see B. I, Chap. LIII. The reference is to archetypal ideas of creation, something akin to the Platonic Ideas, the "multitude of things intelligible," discussed in Chap. L-LV of this book. The 'Saracen jurists' (Saracenorum in jure loquentium) are apparently Avicenna and his school, against whom these chapters are directed."