An easier (relatively speaking, considering you have been reading along thus far) article today, proving God does not look like His popular depictions, i.e. that He has no extraneous properties.
Chapter 23: There Is No Accident In God
1 FROM this truth it follows of necessity that nothing can accrue to God besides His essence, nor anything be accidentally in Him.i
2 For existence itself cannot participate in something that is not of its essence; although that which exists can participate in something else. Because nothing is more formal or more simple than existence. Hence existence itself can participate in nothing. Now the divine substance is existence itself. Therefore He has nothing that is not of His substance. Therefore no accident can be in Him.ii
3 Moreover. Whatever is in a thing accidentally, has a cause of being there: since it is added to the essence of that in which it is. Therefore if anything is in God accidentally, this must be through some cause. Consequently the cause of the accident is either the divine substance itself, or something else. If it is something else, this other thing must act on the divine substance; since nothing introduces a form whether substantial or accidental, into some recipient, unless in some way it act upon that recipient: because to act is nothing but to make something to be actual, and it is this by a form.
Wherefore God will be passive and movable to some agent: which is against what has been decided above. If, on the other hand, the divine substance itself is the cause of the accident that is in it, then it is impossible for it to be its cause as receiving it, since then the same thing in the same respect would make itself to be in act. Therefore, if there is an accident in God, it follows that He receives that accident in one respect, and causes it in another, even as bodies receive their proper accidents through the nature of their matter, and cause them through their form: so that God, therefore, will be composite, the contrary of which has been proved above.iii
4 Again. Every subject of an accident is compared thereto as potentiality to act: because an accident is a kind of form making a thing to exist actually according to accidental existence. But there is no potentiality in God, as shown above. Therefore there can be no accident in Him.iv
5 Moreover. Everything in which something is accidentally is in some way changeable as to its nature: since an accident, by its very nature, may be in a thing or not in it. Therefore if God has something that becomes Him accidentally, it follows that He is changeable: the contrary of which has been proved above.v
6 Further. Everything that has an accident in itself, is not whatever it has in itself, because an accident is not of the essence of its subject.vi But God is whatever He has in Himself. Therefore no accident is in God. The middle proposition is proved as follows. A thing is always to be found more excellently in the cause than in the effect. But God is the cause of all things. Therefore whatever is in Him, is found in Him in the most perfect way. Now that which is most perfectly becoming to a thing, is that thing itself: because it is more perfectly one than when one thing is united to another substantially as form is united to matter: which union again is more perfect than when one thing is in another accidentally. It follows therefore that God is whatever He has.vii
7 Again. Substance is not dependent upon accident, although accident depends on substance. Now that which is not dependent upon another, can sometimes be found without it. Therefore some substance can be found without an accident: and this seemingly is most becoming to a supremely simple substance, such as the divine substance. Therefore the divine substance is altogether without accidents.viii
9 …Having established this truth we are able to refute certain erroneous statements in the law of the Saracens to the effect that the divine essence has certain forms added thereto.ix
iThis follows, probably obviously, from God’s essence being His existence (last week). Think of it like if existence = essence, then there’s no room for accident’s. What can be an “accident”, i.e. an unessential property, of existence itself?
ii“that which exists can participate in something else.” You exist, and accidentally (in this sense) have characteristics that other human beings might or might not have. None of these accidents change your essence, which is that of a rational being. The rest follows simply from point 1.
iiiA lot of words, which I trust you read carefully. If there was an accident in God, it must have been caused. By what? The only possibility is God. But that would make Him composite, and we have already proved He is not made of parts, and (as we’ll need next) He has no potentiality. Thus this proof is pretty simple.
ivYou remember act versus potential, I trust? That it takes a cause, i.e. something actual, to turn a potentiality into an actuality? The rest follows.
vThe footnote is, as it often is, to Chapter 13, which proves God is the Unchanging Changer slash Unmoved Mover. Not too different than proof 3, then.
viThe middle term is “an accident is not of the essence of its subject.”
viiThe rest is really proving existence and essence are one in God again, though the roundabout way. A cause is more than its effect, and cause cannot give what it doesn’t have. Good analogy I once read is that the cause of the water becoming red is red dye, but the red dye will necessarily be redder (or no less red) than the water. The rest follows, but it is admittedly a bit of a tangle.
viiiThis obviously follows from the material above; it doesn’t survive on its own. But note what simple means: without accidents or parts, without potentiality. It is not a synonym of “less” or the like.
ixI left this in only to prove what we already know. That disputes are ever with us.
 Ch. xxii
 Ch. xiii.
 Ch. xviii.
 Ch. xvi.
 Ch. xiii.
 Cf. ch. xiii: Again it any two things . . . p. 28.
 Ch. xviii.
 v. 4.