The Knowledge of the Creatures is Useful to Avoid Errors Concerning God
Summa Contra Gentiles, Book II, cc. 2-3
Chapter 2: That the Consideration of Creatures is Useful for Instruction of Faith
This sort of meditation on the divine works is indeed necessary for instruction of faith in God.
First, because meditation on His works enables us in some measure to admire and reflect upon His wisdom. For things made by art are representative of the artist itself, being made in the likeness of the artist. Now, God brought things into being by His wisdom; wherefore the Psalm (103: 24) declares: "Thou hast made all things in wisdom." Hence, from reflection upon God's works we are able to infer His wisdom, since, by a certain communication of His likeness, it is spread abroad in the things He has made. For it is written: "He poured her out," namely, wisdom, "upon all His works" (Ecc 1:10). Therefore, the Psalmist, after saying: "Thy knowledge is become wonderful to me: it is high, and I cannot reach it," and after referring to the aid of the divine illumination, when be says: "Night shall be my light," etc., confesses that he was aided in knowing the divine wisdom by reflection upon God's works, saying: "Wonderful are Thy works, and my soul knoweth right well" (Ps. 138:6, 11, 14).
Secondly, this consideration [of God's works] leads to admiration of God's sublime power, and consequently inspires in men's hearts reverence for God. For the power of the worker is necessarily understood to transcend the things made. And so it is said: "If they," namely, the philosophers, "admired their power and effects," namely of the heavens, stars, and elements of the world, "let them understand that He that made them is mightier than they" (Wis 13:4). Also it is written: "The invisible things of God are clearly seen, being understood by the things that are made: His eternal power also and divinity" (Rom 1:20). Now, the fear and reverence of God result from this admiration. Hence, it is said: "Great is Thy name in might. Who shall not fear Thee, O King of Nations?" (Jer 10:6-7).
Thirdly, this consideration incites the souls of men to the love of God's goodness. For whatever goodness and perfection is distributed to the various creatures, in partial or particular measure, is united together in Him universally, as in the source of all goodness, as we proved in Book I [ch. 28 and 40]. If, therefore, the goodness, beauty, and delightfulness of creatures are so alluring to the minds of men, the fountainhead of God's own goodness, compared with the rivulets of goodness found in creatures, will draw the enkindled minds of men wholly to Itself. Hence it is said in the Psalm (91:5): "Thou hast given me, O Lord, a delight in Thy doings, and in the works of Thy hands I shall rejoice." And elsewhere it is written concerning the children of men: "They shall be inebriated with the plenty of Thy house," that is, of all creatures, "and Thou shalt make them drink of the torrent of Thy pleasure: for with Thee is the fountain of life" (Ps 35:9-10). And, against certain men, it is said: "By these good things that are seen," namely, creatures, which are good by a kind of participation, "they could not understand Him that is" (Wis 13:1) namely, truly good; indeed, is goodness itself, as was shown in Book I [ch 38].
Fourthly, this consideration endows men with a certain likeness to God's perfection. For it was shown in Book I that, by knowing Himself, God beholds all other things in Himself [Book I, chps. 49-55]. Since, then, the Christian faith teaches man principally about God, and makes him know creatures by the light of divine revelation, there arises in man a certain likeness of God's wisdom. So it is said: "But we all beholding the glory of the Lord with open face, are transformed into the same image" (II Cor 3:18).
It is therefore evident that the consideration of creatures has its part to play in building the Christian faith. And for this reason it is said: "I will remember the works of the Lord, and I will declare the things I have seen: by the words of the Lord are His works" (Ecc 42:15)
Chapter 3: That Knowledge of the Nature of Creatures Serves to Destroy Errors Concerning God
The consideration of creatures is further necessary, not only for the building up of truth, but also for the destruction of errors. For errors about creatures sometimes lead one astray from the truth of faith, so far as the errors are inconsistent with true knowledge of God. Now, this happens in many ways.
First, because through ignorance of the nature of creatures men are sometimes so far perverted as to set up as the first cause and as God that which can only receive its being from something else; for they think that nothing exists beyond the realm of visible creatures. Such were those who identified God with this, that, and the other kind of body; and of these it is said: "Who have imagined either the fire, or the wind, or the swift air, or the circle of the stars, or the great water, or the sun and moon to be the gods" (Wis 13:2).
Secondly, because they attribute to certain creatures that which belongs only to God. This also results from error concerning creatures. For what is incompatible with a thing's nature is not ascribed to it except through ignorance of its nature - as if man were said to have three feet. Now, what belongs solely to God is incompatible with the nature of a created thing, just as that which is exclusively man's is incompatible with another thing's nature. Thus, it is from ignorance of the creature's nature that the aforesaid error arises. And against this error it is said: "They gave the incommunicable name to stones and wood" (Wis 14:23). Into this error fell those who attribute the creation of things, or knowledge of the future, or the working of miracles to causes other than God.
Thirdly, because through ignorance of the creature's nature something is subtracted from God's power in its working upon creatures. This is evidenced in the case of those who set up two principles of reality; in those who assert that things proceed from God, not by the divine will, but by natural necessity; and again, in those who withdraw either all or some things from the divine providence, or who deny that it can work outside the ordinary course of things. For all these notions are derogatory to God's power. Against such persons it is said: "Who looked upon the Almighty as if He could do nothing" (Job 22:17), and: "Thou showest Thy power, when men will not believe Thee to be absolute in power" (Wis 12:17).
Fourthly, through ignorance of the nature of things, and, consequently, of his own place in the order of the universe, this rational creature, man, who by faith is led to God as his last end, believes that be is subject to other creatures to which he is in fact superior. Such is evidently the case with those who subject human wills to the stars, and against these it is said: "Be not afraid of the signs of heaven, which the heathens fear" (Jer 10:2); and this is likewise true of those who think that angels are the creators of souls, that human souls are mortal, and, generally, of persons who hold any similar views derogatory to the dignity of man.
It is, therefore, evident that the opinion is false of those who asserted that it made no difference to the truth of the faith what anyone holds about creatures, so long as one thinks rightly about God, as Augustine tells us in his book On the Origin of the Soul [IV, 4]. For error concerning creatures, by subjecting them to causes other than God, spills over into false opinion about God, and takes men's minds away from Him, to whom faith seeks to lead them.
For this reason Scripture threatens punishment to those who err about creatures, as to unbelievers, in the words of the Psalm (27:5): "Because they have not understood the works of the Lord and the operations of His hands, Thou shalt destroy them, and shalt not build them up"; and: "These things they thought and were deceived," and further on: "They esteemed not the honor of holy souls" (Wis 2.21-22).
Summa contra Gentiles, Book II, cc. 2-3, translated by James F. Anderson (Notre Dame - London: University of Notre Dame Press, 1995), pp.30-34.