We’re still in the throat-clearing stage of Book II. Merry Christmas. Although it may be obvious, by “knowledge of creatures” Aquinas means what we call Science. The Bible demands we do good science, as will be seen.
 THE consideration of creatures is likewise necessary not only for the building up of faith, but also for the destruction of errors. For errors about creatures sometimes lead one astray from the truth of faith, in so far as they disagree with true knowledge of God. This happens in several ways.
 First, because through ignorance of the nature of creatures men are sometimes so far misled as to deem that which can but derive its being from something else, to be the first cause and God, for they think that nothing exists besides visible creatures. Such were those who thought that any kind of body was God: of whom it is said (Wis. xiii. 2): 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.
Notes Ellipsis original (here and below). Interesting that the book of Wisdom is expurgated among protesting Christians. (Of what they are still protesting is a mystery to most.)
 Secondly, because they ascribe to certain creatures that which belongs to God alone. This also results from error about creatures: for one does not ascribe to a thing that which is incompatible with its nature, unless one is ignorant of its nature: for instance if we were to ascribe three feet to a man. Now that which belongs to God alone is incompatible with the nature of a creature: even as that which belongs to man alone is incompatible with another thing’s nature. Hence the foregoing error arises from ignorance of the creature’s nature. Against this error it is said (Wis. xiv. 21): They gave the incommunicable name to stones and wood. Into this error fell those who ascribe the creation of things, or the knowledge of the future, or the working of miracles to causes other than God.
Notes & Update See the correction by YOS below, which is on the money as usual. The main point is scientific and of broad consequence: “one does not ascribe to a thing that which is incompatible with its nature, unless one is ignorant of its nature”. As Thomas himself was, in a very minor way. But as our culture is, in a growing and major way.
 Thirdly, because something is withdrawn from the divine power in its working on creatures, through ignorance of the creature’s nature. This is evidenced in those who ascribe to things a twofold principle, and in those who aver that things proceed from God, not by the divine will, but by natural necessity, and in those who withdraw either all or some things from divine providence, or who deny that it can work outside the ordinary course of things. For all these are derogatory to the divine power. Against these it is said (Job xxii. 17): Who…looked upon the Almighty as if He could do nothing, and (Wis. xii. 17): Thou showest Thy power, when men will not believe Thee to be absolute in power.
Notes Back to science here, or what science has forgotten. God is the primary or first cause of every change. I mean every as in every, without exception. Nothing happens without God. Even your sins. Scary, no?
 Fourthly. Man, who is led by faith to God as his last end, through ignoring the natures of things, and consequently the order of his place in the universe, thinks himself to be beneath certain creatures above whom he is placed: as evidenced in those who subject man’s will to the stars, and against these it is said (Jerem. x. 2): Be not afraid of the signs of heaven, which the heathens fear; also in those who deem the angels to be the creators of souls, and human souls to be mortal; and in those who hold any like opinions derogatory to the dignity of man.
Notes Astrology is not as popular as once was. Except in the sense that certain persons would screen folks not for their birth signs but for their “genes.”
 Accordingly it is clear that the opinion is false of those who asserted that it mattered not to the truth of faith what opinions one holds about creatures, so long as one has right opinion about God, as Augustine relates in his book De Origine Animae: since error concerning creatures by subjecting the human mind to causes other than God amounts to a false opinion about God, and misleads the minds of men from God, to Whom faith strives to lead them.
Notes What’s this? We’re back at science yet again! And Saint Thomas is saying science is important. We should get it right! Scientific errors lead us away from God. Science does itself a momentous disservice considering only physics and not metaphysics. Metaphysical knowledge is surer than mere scientific knowledge. That means if there are any “incompatibilities” between science and God, it means scientists have slipped up somewhere. Being that scientists are human, this should come as no surprise. But yet it does.
 Wherefore Scripture threatens punishment to those who err about creatures, as to unbelievers, in the words of the psalm: 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 (Wis. ii. 21): These things they thought and were deceived, and further on: They esteemed not the honour of holy souls.
Notes Even scripture is in favor of doing good science.