Summa Theologica, by St. Thomas Aquinas, [1947], at sacred-texts.com
We next consider the goodness of God; under which head there are four points of inquiry:
(1) Whether goodness belongs to God?
(2) Whether God is the supreme good?
(3) Whether He alone is essentially good?
(4) Whether all things are good by the divine goodness?
Objection 1: It seems that to be good does not belong to God. For goodness consists in mode, species and order. But these do not seem to belong to God; since God is immense and is not ordered to anything else. Therefore to be good does not belong to God.
Objection 2: Further, the good is what all things desire. But all things do not desire God, because all things do not know Him; and nothing is desired unless it is known. Therefore to be good does not belong to God.
On the contrary, It is written (Lam. 3:25): "The Lord is good to them that hope in Him, to the soul that seeketh Him."
I answer that, To be good belongs pre-eminently to God. For a thing is good according to its desirableness. Now everything seeks after its own perfection; and the perfection and form of an effect consist in a certain likeness to the agent, since every agent makes its like; and hence the agent itself is desirable and has the nature of good. For the very thing which is desirable in it is the participation of its likeness. Therefore, since God is the first effective cause of all things, it is manifest that the aspect of good and of desirableness belong to Him; and hence Dionysius (Div. Nom. iv) attributes good to God as to the first efficient cause, saying that, God is called good "as by Whom all things subsist."
Reply to Objection 1: To have mode, species and order belongs to the essence of caused good; but good is in God as in its cause, and hence it belongs to Him to impose mode, species and order on others; wherefore these three things are in God as in their cause.
Reply to Objection 2: All things, by desiring their own perfection, desire God Himself, inasmuch as the perfections of all things are so many similitudes of the divine being; as appears from what is said above (Q[4] , A[3]). And so of those things which desire God, some know Him as He is Himself, and this is proper to the rational creature; others know some participation of His goodness, and this belongs also to sensible knowledge; others have a natural desire without knowledge, as being directed to their ends by a higher intelligence.
Objection 1: It seems that God is not the supreme good. For the supreme good adds something to good; otherwise it would belong to every good. But everything which is an addition to anything else is a compound thing: therefore the supreme good is a compound. But God is supremely simple; as was shown above (Q[3], A[7]). Therefore God is not the supreme good.
Objection 2: Further, "Good is what all desire," as the Philosopher says (Ethic. i, 1). Now what all desire is nothing but God, Who is the end of all things: therefore there is no other good but God. This appears also from what is said (Lk. 18:19): "None is good but God alone." But we use the word supreme in comparison with others, as e.g. supreme heat is used in comparison with all other heats. Therefore God cannot be called the supreme good.
Objection 3: Further, supreme implies comparison. But things not in the same genus are not comparable; as, sweetness is not properly greater or less than a line. Therefore, since God is not in the same genus as other good things, as appears above (Q[3], A[5]; Q[4], A[3]) it seems that God cannot be called the supreme good in relation to others.
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 to Objection 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 to Objection 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 to Objection 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.
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.
Objection 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.
Objection 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 to Objection 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 to Objection 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 to Objection 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.
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.
Objection 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]).
Everything is therefore called good from the divine goodness, as from the first exemplary effective and final principle of all goodness. Nevertheless, everything is called good by reason of the similitude of the divine goodness belonging to it, which is formally its own goodness, whereby it is denominated good. And so of all things there is one goodness, and yet many goodnesses.
This is a sufficient Reply to the Objections.