Thomas Aquinas - Summa Theologica, Part I (Prima Pars)

On the contrary, Augustine says (De Trin. ii) that, the Trinity of the divine persons is "the supreme good, discerned by purified minds."

I answer that, God is the supreme good simply, and not only as existing in any genus or order of things. For good is attributed to God, as was said in the preceding article, inasmuch as all desired perfections flow from Him as from the first cause. They do not, however, flow from Him as from a univocal agent, as shown above (Q. 4, A. 2); but as from an agent which does not agree with its effects either in species or genus. Now the likeness of an effect in the univocal cause is found uniformly; but in the equivocal cause it is found more excellently, as, heat is in the sun more excellently than it is in fire. Therefore as good is in God as in the first, but not the univocal, cause of all things, it must be in Him in a most excellent way; and therefore He is called the supreme good.

Reply Obj. 1: The supreme good does not add to good any absolute thing, but only a relation. Now a relation of God to creatures, is not a reality in God, but in the creature; for it is in God in our idea only: as, what is knowable is so called with relation to knowledge, not that it depends on knowledge, but because knowledge depends on it. Thus it is not necessary that there should be composition in the supreme good, but only that other things are deficient in comparison with it.

Reply Obj. 2: When we say that good is what all desire, it is not to be understood that every kind of good thing is desired by all; but that whatever is desired has the nature of good. And when it is said, "None is good but God alone," this is to be understood of essential goodness, as will be explained in the next article.

Reply Obj. 3: Things not of the same genus are in no way comparable to each other if indeed they are in different genera. Now we say that God is not in the same genus with other good things; not that He is any other genus, but that He is outside genus, and is the principle of every genus; and thus He is compared to others by excess, and it is this kind of comparison the supreme good implies. _______________________

THIRD ARTICLE [I. Q. 6, Art. 3]

Whether to Be Essentially Good Belongs to God Alone?

Objection 1: It seems that to be essentially good does not belong to God alone. For as one is convertible with being, so is good; as we said above (Q. 5, A. 1). But every being is one essentially, as appears from the Philosopher (Metaph. iv); therefore every being is good essentially.

Obj. 2: Further, if good is what all things desire, since being itself is desired by all, then the being of each thing is its good. But everything is a being essentially; therefore every being is good essentially.

Obj. 3: Further, everything is good by its own goodness. Therefore if there is anything which is not good essentially, it is necessary to say that its goodness is not its own essence. Therefore its goodness, since it is a being, must be good; and if it is good by some other goodness, the same question applies to that goodness also; therefore we must either proceed to infinity, or come to some goodness which is not good by any other goodness. Therefore the first supposition holds good. Therefore everything is good essentially.

On the contrary, Boethius says (De Hebdom.), that "all things but God are good by participation." Therefore they are not good essentially.

I answer that, God alone is good essentially. For everything is called good according to its perfection. Now perfection of a thing is threefold: first, according to the constitution of its own being; secondly, in respect of any accidents being added as necessary for its perfect operation; thirdly, perfection consists in the attaining to something else as the end. Thus, for instance, the first perfection of fire consists in its existence, which it has through its own substantial form; its secondary perfection consists in heat, lightness and dryness, and the like; its third perfection is to rest in its own place. This triple perfection belongs to no creature by its own essence; it belongs to God only, in Whom alone essence is existence; in Whom there are no accidents; since whatever belongs to others accidentally belongs to Him essentially; as, to be powerful, wise and the like, as appears from what is stated above (Q. 3, A. 6); and He is not directed to anything else as to an end, but is Himself the last end of all things. Hence it is manifest that God alone has every kind of perfection by His own essence; therefore He Himself alone is good essentially.

Reply Obj. 1: "One" does not include the idea of perfection, but only of indivision, which belongs to everything according to its own essence. Now the essences of simple things are undivided both actually and potentially, but the essences of compounds are undivided only actually; and therefore everything must be one essentially, but not good essentially, as was shown above.

Reply Obj. 2: Although everything is good in that it has being, yet the essence of a creature is not very being; and therefore it does not follow that a creature is good essentially.

Reply Obj. 3: The goodness of a creature is not its very essence, but something superadded; it is either its existence, or some added perfection, or the order to its end. Still, the goodness itself thus added is good, just as it is being. But for this reason is it called being because by it something has being, not because it itself has being through something else: hence for this reason is it called good because by it something is good, and not because it itself has some other goodness whereby it is good. _______________________

FOURTH ARTICLE [I, Q. 6, Art. 4]

Whether All Things Are Good by the Divine Goodness?

Objection 1: It seems that all things are good by the divine goodness. For Augustine says (De Trin. viii), "This and that are good; take away this and that, and see good itself if thou canst; and so thou shalt see God, good not by any other good, but the good of every good." But everything is good by its own good; therefore everything is good by that very good which is God.

Obj. 2: Further, as Boethius says (De Hebdom.), all things are called good, accordingly as they are directed to God, and this is by reason of the divine goodness; therefore all things are good by the divine goodness.

On the contrary, All things are good, inasmuch as they have being. But they are not called beings through the divine being, but through their own being; therefore all things are not good by the divine goodness, but by their own goodness.

I answer that, As regards relative things, we must admit extrinsic denomination; as, a thing is denominated "placed" from "place," and "measured" from "measure." But as regards absolute things opinions differ. Plato held the existence of separate ideas (Q. 84, A. 4) of all things, and that individuals were denominated by them as participating in the separate ideas; for instance, that Socrates is called man according to the separate idea of man. Now just as he laid down separate ideas of man and horse which he called absolute man and absolute horse, so likewise he laid down separate ideas of "being" and of "one," and these he called absolute being and absolute oneness; and by participation of these, everything was called "being" or "one"; and what was thus absolute being and absolute one, he said was the supreme good. And because good is convertible with being, as one is also; he called God the absolute good, from whom all things are called good by way of participation.

Although this opinion appears to be unreasonable in affirming separate ideas of natural things as subsisting of themselves—as Aristotle argues in many ways—still, it is absolutely true that there is first something which is essentially being and essentially good, which we call God, as appears from what is shown above (Q. 2, A. 3), and Aristotle agrees with this. Hence from the first being, essentially such, and good, everything can be called good and a being, inasmuch as it participates in it by way of a certain assimilation which is far removed and defective; as appears from the above (Q. 4, A. 3).