Chapter 39: THAT THERE CANNOT BE EVIL IN GOD [Quod in Deo non potest esse malum]
 From this [viz. the substantial goodness of God, cf. SCG I, 38] it is quite evident that there cannot be evil in God.
 For being and goodness, and all names that are predicated essentially [omnia quae per essentiam dicuntur], have nothing extraneous mixed with them, although that which is or good can have something besides being and goodness. For nothing prevents the subject of one perfection from being the subject of another, just as that which is a body can be white and sweet. Now, each nature is enclosed within the limits of its notion [unaquaeque autem natura suae rationis termino concluditur], so that it cannot include anything extraneous within itself [nihil extraneum intra se capere possit]. But, as we have proved, God is goodness, and not simply good [Deus autem est bonitas, non solum bonus]. There cannot, therefore, be any non-goodness in Him [Non potest igitur in eo esse aliquid non bonitas]. Thus, there cannot possibly be evil in God.
 Moreover, what is opposed to the essence of a given thing cannot befit that thing so long as its essence remains. Thus, irrationality or insensibility cannot befit man unless he ceases to be a man [sicut homini non potest convenire irrationalitas vel insensibilitas nisi homo esse desistat]. But the divine essence is goodness itself, as we have shown. Therefore, evil, which is the opposite of good, could have no place in God—unless He ceased to be God, which is impossible [Ergo malum, quod est bono oppositum, in eo locum habere non potest nisi esse desisteret. Quod est impossibile], since He is eternal, as we have shown.
 Furthermore, since God is His own being, nothing can be said of Him by participation [nihil participative de ipso dici potest], as is evident from the above argument. If, then, evil is said of God, it will not be said by participation, but essentially. But evil cannot be so said of anything as to be its essence, for it would lose its being [malum de nullo dici potest ut sit essentia alicuius: ei enim esse deficeret], which is a good, as we have shown. In evil, however, there can be nothing extraneous mixed with it, as neither in goodness. Evil, therefore, cannot be said of God.
 Again, evil is the opposite of good. But the nature of the good consists in perfection, which means that the nature of evil consists in imperfection [i.e. inverted, regressive teleology]. Now, in God, Who is universally perfect, as we have shown above, there cannot be defect or imperfection. Therefore, evil cannot be in God.
 Then, too, a thing is perfect according as it is in act. A thing will therefore be imperfect according as it falls short of act [imperfectum erit secundum quod est deficiens ab actu]. Hence, evil is either a privation or includes privation. But the subject of privation is potency, which cannot be in God. Neither, therefore, can evil.
Annotated: "Denied by Buddhists, and by other Asiatic-minded and dissatisfied persons, who will have it that being is thought, or will, and that thought, will, and all conscious effort is misery."
 If, moreover, the good is “that which is sought by all,” it follows that every nature flees evil as such [malum unaquaeque natura refugit inquantum huiusmodi]. Now, what is in a thing contrary to the motion of its natural appetite is violent and unnatural. Evil in each thing, consequently, is violent and unnatural, so far as it is an evil for that thing; although, among composite things, evil may he natural to a thing according to something within it. But God is not composite, nor, as we have shown, can there be anything violent or unnatural in Him. Evil, therefore, cannot be in God.
 Scripture likewise confirms this. For it is said in the canonic Epistle of John (I, 1:5): “God is light and in Him there is no darkness”; and in Job (34:10) it is written: “Far from God be wickedness; and iniquity from the Almighty.”
Chapter 40: THAT GOD IS THE GOOD OF EVERY GOOD [Quod Deus est omnis omni bonum]
 From the foregoing it is also shown that God is “the good of every good.”’
 For the goodness of each thing is its perfection, as we have said. But, since God is absolutely perfect, in His perfection He comprehends the perfections of all things [sua perfectione omnes rerum perfectiones comprehendit], as has been shown [cf. SCG I, 31?]. His goodness, therefore, comprehends every goodness. Thus, He is the good of every good.
 Moreover, that which is said to be of a certain sort by participation is said to be such only so far as it has a certain likeness to that which is said to be such by essence. Thus iron is said to be on fire in so far as it participates in a certain likeness of fire [inquantum quandam similitudinem ignis participat]. But God is good through His essence, whereas all other things are good by participation, as has been shown. Nothing, then, will be called good except in so far as it has a certain likeness of the divine goodness. Hence, God is the good of every good.
 Since, furthermore, each thing is appetible because of the end, and since the nature of the good consists in its being appetible, each thing must be called good either because it is the end or because it is ordered to the end [boni autem ratio consistat in hoc quod est appetibile: oportet quod unumquodque dicatur bonum vel quia est finis, vel quia ordinatur ad finem]. It is the last end, then, from which all things receive the nature of good [Finis igitur ultimus est a quo omnia rationem boni accipiunt]. As will be proved later on, this is God. God is, therefore, the good of every good [Est igitur Deus omnis boni bonum].
 Hence it is that God, promising to Moses a vision of Himself, says: “I will show you all good” (Exod. 33:19). And in Wisdom (7:11), it is said of the divine wisdom: “All good things come to me together with her.”
Chapter 41: THAT GOD IS THE HIGHEST GOOD [Quod Deus sit summum bonum]
 From this conclusion we prove that God is the highest good.
 For the universal good stands higher than any particular good, just as “the good of the people is better than the good of an individual,” since the goodness and perfection of the whole stand higher than the goodness and perfection of the part. But the divine goodness is compared to all others as the universal good to a particular good, being, as we have shown, the good of every good [omnis boni bonum]. God is, therefore, the highest good.
 Furthermore, what is said essentially is said more truly than what is said by participation. But God is good essentially, while other things are good by participation, as we have shown. God is, therefore, the highest good.
 Again, “what is greatest in any genus is the cause of the rest in that genus,” [Quod est maximum in unoquoque genere est causa aliorum quae sunt in illo genere] for a cause ranks higher than an effect [causa enim potior est effectu]. But, as we have shown, it is from God that all things have the nature of good. God is, therefore, the highest good.
This is a key passage for understanding the fourth way in the Summa theologica I, 2, 3, which in turn must be read in conjunction with SCG I, 38: each thing's good is the motor for its act of being, its formal perfection, and, as God is the highest good and cause of all beings' be-ing, so He is the perfection of every formal category of being, though He is not properly contained within any genus (cf. SCG I, 25–27).
 Moreover, just as what is not mixed with black is more white, so what is not mixed with evil is more good. But God is most unmixed with evil, because evil can be in God neither in act nor in potency; and this belongs to God according to His nature, as we have shown. God is, therefore, the highest good.
 Hence what is written in 1 Samuel (2:2): “There is none holy as the Lord is.”