—Compendium Theologiae, 11.
● "God is infinite, comprehending in Himself all the plenitude of perfection of all being, He cannot acquire anything new, nor extend Himself to anything whereto He was not extended previously. Hence movement in no way belongs to Him."
—Summa Theologica, I, q. 9, a. 1
● "God alone is altogether immutable; whereas every creature is in some way mutable. Be it known therefore that a mutable thing can be called so in two ways: by a power in itself; and by a power possessed by another. For all creatures before they existed, were possible, not by any created power, since no creature is eternal, but by the divine power alone, inasmuch as God could produce them into existence. Thus, as the production of a thing into existence depends on the will of God, so likewise it depends on His will that things should be preserved; for He does not preserve them otherwise than by ever giving them existence; hence if He took away His action from them, all things would be reduced to nothing, as appears from Augustine (Gen. ad lit. iv, 12). Therefore as it was in the Creator's power to produce them before they existed in themselves, so likewise it is in the Creator's power when they exist in themselves to bring them to nothing. In this way therefore, by the power of another—namely, of God—they are mutable, inasmuch as they are producible from nothing by Him, and are by Him reducible from existence to non-existence."
—Summa Theologica, I, q. 9, a. 2
● “After dividing higher being in general, into three grades, in which the first is above eternity, which belongs to the first cause, the second with eternity, which belongs to an intelligence, and the third below eternity and above time, which belongs to the soul, the author of this book begins here to investigate these three grades.”
—Commentary on the Book of Causes (Liber de Causis), Proposition 6.
● "As we attain to the knowledge of simple things by way of compound things, so must we reach to the knowledge of eternity by means of time, which is nothing but the numbering of movement by "before" and "after." For since succession occurs in every movement, and one part comes after another, the fact that we reckon before and after in movement, makes us apprehend time, which is nothing else but the measure of before and after in movement. Now in a thing bereft of movement, which is always the same, there is no before or after. As therefore the idea of time consists in the numbering of before and after in movement; so likewise in the apprehension of the uniformity of what is outside of movement, consists the idea of eternity.
"Further, those things are said to be measured by time which have a beginning and an end in time, because in everything which is moved there is a beginning, and there is an end. But as whatever is wholly immutable can have no succession, so it has no beginning, and no end.
"Thus eternity is known from two sources: first, because what is eternal is interminable—that is, has no beginning nor end (that is, no term either way); secondly, because eternity has no succession, being simultaneously whole."
—Summa Theologica, I, q. 10, a. 1
● "It is manifest that time and eternity are not the same. Some have founded this difference on the fact that eternity has neither beginning nor an end; whereas time has a beginning and an end. This, however, makes a merely accidental, and not an absolute difference because, granted that time always was and always will be, according to the idea of those who think the movement of the heavens goes on for ever, there would yet remain a difference between eternity and time, as Boethius says (De Consol. v), arising from the fact that eternity is simultaneously whole; which cannot be applied to time: for eternity is the measure of a permanent being; while time is a measure of movement."
—Summa Theologica, I, q. 10, a. 4
● “Since we are asking what time is, we must begin by inquiring how time pertains to motion, It is clear that time does pertain to motion because we sense motion and time together. It happens that sometimes we perceive a passage of time, even when we are in the dark and do not see the motion of any exterior body. And if we do not suffer any alteration in our bodies from an exterior agent, we will not sense any motion of a sensible body. Nevertheless, if some motion occurs in our soul, for example, a succession of thoughts and images, it immediately seems to us that some time has passed. Thus by perceiving some sort of motion, we perceive time. And conversely, when we perceive time, we also perceive motion. Hence, since time is not motion itself, as was proven, it follows that time pertains to motion.”
—Commentary on Aristotle’s Physics, Book 4, Lect. 17.
● "Two things are to be considered in time: time itself, which is successive; and the "now" of time, which is imperfect. Hence the expression "simultaneously-whole" is used to remove the idea of time, and the word "perfect" is used to exclude the "now" of time."
—Summa Theologica, I, q. 10, a. 1, ad 5
● "The "now" that stands still, is said to make eternity according to our apprehension. As the apprehension of time is caused in us by the fact that we apprehend the flow of the "now," so the apprehension of eternity is caused in us by our apprehending the "now" standing still. When Augustine says that "God is the author of eternity," this is to be understood of participated eternity. For God communicates His eternity to some in the same way as He communicates His immutability."
—Summa Theologica, I, q. 10, a. 2, ad 1
● “The “now” of time is not time, the “now” of eternity is really the same as eternity.”
—Commentary, I Sentences, 19, 2, 2.
● "On the part of cognition or knowledge it should be noted that in knowing things that take place according to the order of time, the cognitive power that is contained in any way under the order of time is related to them in another way than the cognitive power that is totally outside of the order of time. The order of place provides a suitable example of this. According to the Philosopher in IV Physicorum [11:219a 14], before and after in movement, and consequently in time, corresponds to before and after in magnitude. Therefore, if there are many men passing along some road, any one of those in the ranks has knowledge of those preceding and following as preceding and following, which pertains to the order of place. Hence any one of them sees those who are next to him and some of those who precede him; but he cannot see those who follow behind him. If, however, there were someone outside of the whole order of those passing along the road, for instance, stationed in some high tower where he could see the whole road, he would at once see all those who were on the road—not under the formality of preceding and subsequent (i.e., in relation to his view) but all at the same time and how one precedes another.
"Now, our cognition falls under the order of time, either per se or accidentally; whence the soul in composing and dividing necessarily includes time, as is said in III De anima [6: 430a 32]. Consequently, things are subject to our cognition under the aspect of present, past, and future. Hence the soul knows present things as existing in act and perceptible by sense in some way; past things it knows as remembered; future things are not known in themselves because they do not yet exist, but can be known in their causes—with certitude if they are totally determined in their causes so that they will take place of necessity; by conjecture if they are not so determined that they cannot be impeded, as in the case of those things that are for the most part; in no way if in their causes they are wholly in potency, i.e., not more determined to one than to another, as in the case of those that are indeterminate to either of two. The reason for this is that a thing is not knowable according as it is in potency, but only according as it is in act, as the Philosopher shows in IX Metaphysicae [9: 1051a 22].
"God, however, is wholly outside the order of time, stationed as it were at the summit of eternity, which is wholly simultaneous, and to Him the whole course of time is subjected in one simple intuition. For this reason, He sees in one glance everything that is effected in the evolution of time, and each thing as it is in itself, and it is not future to Him in relation to His view as it is in the order of its causes alone (although He also sees the very order of the causes), but each of the things that are in whatever time is seen wholly eternally as the human eye sees Socrates sitting, not in its causes but in itself."
—Commentary, I Peri Hermeneias, Lesson 14
● "Thus eternity is totally at once, just as a point lacks parts that are distinct in location. For a point can be compared to a line in two ways: first as included in the line, whether at the beginning, middle or end, secondly as existing outside a line. A point within a line cannot be present to all the parts of the line, but in different parts of the line different points must be designated. But a point outside the line can view all parts of the line equally, as in a circle, whose central point is indivisible and faces all the parts of the circumference and all of them are somehow present to it, although not to one another.
"An instant, which is a limit of time, is comparable to the point included in a line. It is not present to all parts of time, but in different parts of time different instances are designated. Eternity is something like the point outside a line, like the centre of a circle. Since it is simple and indivisible, it comprehends the whole passage of time and each part of time is equally present to it, although one part of time follows another."
—De Rationibus Fidei, 10.
~St. Thomas Aquinas
Triumph of St. Thomas Aquinas, by Benozzo Gozzoli
Tempera on panel, 1471; Musée du Louvre, Paris.
