Commentaria in Summam contra Gentiles, Liber I

After Saint Thomas has shown the way of arriving at knowledge of the divine, he now, following the manner handed down, proceeds to the exposition of the divine things ¹. In regard to this he does three things: first, he removes from God the imperfection of temporal being; second, the imperfection of passive potency, in the following chapter; third, the imperfection of composition, in chapter XVIII.

I. As to the first, he proposes this conclusion: God is eternal.

It is proved first ². That which begins or ceases to be undergoes this through motion or change. God is altogether immutable. Therefore He does not begin or cease to be.

Note here that motion or change can be taken in two ways. In one way, for the passage that occurs between esse and non-esse with some subject presupposed: this is called physical change. In the other way, for every succession between esse and non-esse, whether a subject is presupposed or not: in this way even that which is newly created or totally annihilated can be said to change, because the former receives esse after non-esse, the latter non-esse after esse. Change must therefore be understood in the major proposition in the second way: for according to this sense too God is altogether immutable, both accidentally and substantially. But not in the first way: for the universe began to be, and yet it did not begin through motion or change properly so called, but through creation.

II. Second. God has esse wholly at once, and does not have esse after non-being, nor non-being after esse. Therefore he is eternal. — The consequence is proved: because in these the reason of eternity consists. — The antecedent, however, is proved. God is not measured by time, since only those things are measured by time which are moved, time being the number of motion. Therefore in him there is no taking of before and after. Hence neither esse after non-being, nor non-being after esse, nor is there succession in his esse. The consequence is proved: because these cannot be understood without time.

It must first be noted that every before and after, or every succession in duration, pertains to the nature of time, since every other duration lacks succession. Therefore "to be measured by time" and "to have a before and after in duration" are convertible. Hence Saint Thomas rightly concludes: It is not measured by time; therefore it has no before and after in its duration.

It must be considered, second, that here Saint Thomas touches upon the account of eternity laid down by Boethius in Book V of the Consolation, where he says that “eternity is the whole, simultaneous, and perfect possession of interminable life.” In explaining this, Saint Thomas, in Iª, q. X, a. 1, says two things. The first is that, “since in every motion there is succession, and a before and after, whereas in that which lacks motion and always remains in the same way there cannot be a before and after; just as the account of time consists in the numbering of before and after in motion, so the account of eternity consists in the apprehension of the uniformity of that which is altogether outside motion. And this is signified when it is said that eternity is whole and simultaneous.” — The second is that “those things are said to be measured by time which have a beginning and an end in time, as is stated in Physics IV. But that which is altogether immutable can have neither succession, nor a beginning, nor an end. And this is signified when that which is measured by eternity is said to be interminable.”

III. But in this explanation, setting the rest aside, there is a doubt as to how it is to be understood that the notion of eternity in the apprehension of a wholly immutable thing consists in uniformity.

For some interpret the Saint Thomas as meaning by apprehension the objective conception: and that to consist in the apprehension of uniformity is the same as to consist in the reason of uniformity.

But since it does not seem that Saint Thomas added superfluously that it consists in apprehension—for if he had held the sense that these men claim, he could have said more briefly and more clearly that the character of eternity consists in the character of uniformity—therefore, with all deference to a better judgment, it seems to me that it can be expounded in two other ways.

2. For the first point, it is supposed that the ratio which the intellect forms concerning some thing is the concept through whose mediation it understands and apprehends the thing. Therefore the ratio of eternity is said to consist in the apprehension of the uniformity of a thing altogether immobile, namely because then, when it apprehends the uniformity of a thing altogether immobile, the intellect forms the concept and ratio of eternity. And from this it follows that the first exposition seems to intend, namely, that the ratio of eternity is esse as the uniformity of a thing altogether immutable.

3. For the second way, it should be noted that, because Saint Thomas wishes to make known the notion of eternity from the notion of time, and just as he says that the notion of time consists in numbering, so he says that the notion of eternity consists in apprehension: therefore, that the notion of eternity consists in apprehension must be explained proportionally to the way in which it is said that the notion of time consists in numbering. Here it must be known that, since time is in some way continuous and in some way discrete, because it is the number of continuous things, namely of before and after in motion, we can speak of time in two ways: namely, with respect to its continuity; and with respect to its discreteness and the separation of its parts. The first belongs to it really according to the esse that it has outside the intellect: for it is truly continuous, just as is the motion that it measures and in which it is. The second, however, belongs to it according as it is apprehended by the soul separating and distinguishing it into parts, for instance into days, months, years, and things of this sort; and likewise separating the first motion into parts corresponding to the parts of time. For this separation is not in the thing, since both the parts of time and the parts of motion outside the intellect are continuous; rather, it is only in the apprehension of the intellect. And it is similar to saying that the number ten, by which intrinsically ten cubits of cloth are numbered, outside the intellect is a continuous quantity, because it is nothing other than the very quantity of the cloth, which is continuous; but in the intellect it exists with respect to that separation into ten units from which such a denary number is constituted integrally. Therefore the notion of time is said to consist in the numbering of before and after in motion, because its completion, which is what is formal in time, namely the very discreteness and separation of the parts of time, which is included in the notion of number, belongs to time through the work of the soul numbering, that is, distinguishing and separating it into several parts and several units. Hence, if the work of the soul is removed, there is indeed in the thing that entity which is time; but it does not have completely the notion of time, because it does not have actual division and separation, and consequently it is not actually number. This seems to be the intention of the Commentator, Physics IV, comment 131, where he says that time in act will not exist unless there is a soul, but in potency it will exist even if there is no soul. It also seems to be the opinion of Saint Thomas in Sentences I, d. xix: for there, q. II, a. 1, and q. v, a. 1, he says that what is formal in time is completed in the operation of the soul numbering; and he compares time to the universal, and he says that the universal is a nature under the intention of universality. He also states the same thing in Physics IV. ³, explaining that text of Aristotle in which he says that time, if the soul does not exist, is in a certain respect.

4. Proportionally, therefore, in eternity we can consider two things: namely, the very unity of the divine esse, altogether immutable; and its measurement insofar as that divine esse measures. The first belongs to it according as it is in reality: for the divine esse is really one outside the intellect. The second, however, belongs to it through the operation of the soul distinguishing the unity of the divine esse from the esse itself, and apprehending it as a certain measure and duration. Since, therefore, the ratio of eternity states that the measuring unity is altogether immutable; and since measuring belongs to it only through the work of the soul distinguishing it from esse and apprehending it under the ratio of measure: therefore the ratio of eternity is not completed except through the work of the soul. Hence, when the soul does not consider it, there is indeed in reality that entity which is eternity: but it does not have the complete ratio of eternity, because it is not a measure according to the esse it has outside the soul, but only according as it is in the apprehension of the soul. Therefore the ratio of eternity is said to consist completely in the apprehension of the uniformity of that which is altogether immutable, because the complement of its ratio, namely being a measure, is only according to the apprehension of the soul: just as the ratio of time is said to consist completely in the numbering of before and after in motion, because the very discretion and distinction of parts, which completes the ratio of time, is only according to the apprehension of the soul numbering and separating both time and motion into parts. — This seems to be the mind of St. Thomas in Prima, q. x, a. 2, ad 3, where he says that God is not called eternal as though he were measured in any way, but the ratio of measure is taken there according to our apprehension alone.

5. It must be further noted that, since St. Thomas seems to intimate that succession is found in the esse of a thing measured by time—when he concludes that no succession is found in the divine esse because it is not measured by time—if we speak of the substantial esse of a temporal thing, it can be understood in two ways. In one way, that it is not whole at once but is acquired part after part. And thus it is not true that it has succession in itself; nor does St. Thomas understand it thus. — In another way, that although it is whole at once and indivisible, it is nevertheless subject to transmutation, when some change occurs for its conservation or cessation; and by reason of this it has succession and divisibility per accidens, because that transmutation is not whole at once. And thus it is true that it has succession. This is the sense St. Thomas intends, as can be gathered from I Sent., d. xix, q. II, 1, ad 4, and Iª IIae, q. xxxi, 2, corp., and Pot. q. v, a. 1, ad 2, and a. 4, ad 1, and from the treatise on Time ⁴

IV. Third. If God was not always, then he was brought forth from non-being to being by another. Therefore God is not the first cause. This is false. Therefore the first as well. — The first consequence is proved. Because nothing is brought forth from non-being to being by itself: since what is not cannot act. — The second is also evident. Because that from which something is produced into being must be prior to it, at least by priority of nature. Then further. He did not begin to be, but always was. Therefore neither will he cease to be. — The consequence is evident. Because what always was has the power of always being. — Therefore he is eternal. Concerning this consequence, "He did not begin to be, therefore neither will he cease to be," there is doubt: because, supposing the eternity of the world (which is possible according to Saint Thomas ⁵), the intelligences did not begin to be; and yet, from without, according to the theologians, they could not be through annihilation. Therefore etc. — Nor does the proof adduced seem to hold. For it can be said that, although what always was has the power of always being, nevertheless that power can be taken away through annihilation. It is answered that something's not beginning to be can happen for a twofold reason: in one way, because it belongs to it essentially to be from eternity, and not to be produced by anything; in another way, because it is produced from eternity by some extrinsic agent. From not beginning to be in the first way, it follows that it will not cease to be, neither from within nor from without: because such is its very esse, and it has the power essentially so as to be always. And Saint Thomas intends that consequence in this sense. — But from not beginning to be in the second way, it does not follow that it cannot cease to be, at least from without. Nor is it necessary that everything of this kind that did not begin should have the power to be always: for man or an ass could have been produced from eternity, and yet would not have the power to be always.

V. Fourth. It is necessary to posit in things something that is necessary of itself. Either, then, that thing has a cause of its necessity, and that cause another cause, and so on to infinity; or one must posit that there is a first necessary being. But an infinite regress cannot be posited. Therefore there must be some being necessary through itself. And this we call God. Therefore God is also eternal: for everything necessary through itself is eternal. The antecedent is proved. Everything possible of being has a cause: for, since it stands equally toward esse and non-esse, its determination to esse cannot come about except from some cause. But there is no infinite regress among causes. Therefore one must arrive at something that is not possible of being. Therefore there must be some being necessary through itself.

2. For the clarification of this proposition, "Whatever is necessary of itself is eternal," it must be considered that something can be said to be necessary of itself in two ways, just as something can be said to be necessary through another. For something is said to be necessary through another either because it has some extrinsic cause productive of its necessity, or because it derives its necessity from another form. Conversely, something is said to be necessary of itself either because it has its necessity from no extrinsic cause, or because it is necessary from its own form and not through another form.

What is said here, therefore, must be understood of the per se necessary in the first mode, as is clear from the course of the argument: not, however, in the second mode. For that which is per se necessary does not have a cause of its esse: since, because the necessity of being is a condition concomitant to esse, if it had esse from another, it would also have its necessity from another; and thus it would not be per se necessary, as we are now speaking of the per se necessary. But everything that does not have a cause of its esse is itself subsistent esse: because, if esse were distinct from its essence, it would not belong to it of itself, since no thing is the efficient cause of its own esse; and thus it would have to receive esse from another. From this, moreover, it follows that it is eternal: because subsistent esse contains every perfection of being and cannot fail.

3. Further, it must be known, with respect to the proposition The possible is equally disposed to esse and non-esse, that "possible" is here taken simply and absolutely. For since the essence of a possible thing is really distinct from actual existence, and, considered in itself, has no esse of itself: speaking absolutely, it is no more inclined to esse than to non-esse, just as it is no more inclined to have that agent produce it than not produce it, but this comes from the disposition of the agent. — But if we were speaking of the possible as matter already disposed by an agent for the introduction of the form, then the possible would not be equally disposed to esse and non-esse, but would be more inclined to esse than to non-esse.

But a doubt arises. For according to the doctrine of Saint Thomas, the nature of a possible thing has non-being of itself: because, if it were left to itself, it would be a non-being, while it has esse from another. Therefore the possible is not related equally to esse and non-esse: for each thing is more inclined toward that which belongs to it of itself than toward that which belongs to it from another.

It is answered that that the nature of a possible thing has non-being from itself can be understood in two ways. In one way, affirmatively: that is, because it determines non-being to itself from its own nature, just as fire determines heat to itself from its own nature. In another way, negatively: namely, because from its own nature it does not determine being to itself; just as we say that the universal is everywhere, because it does not determine any place to itself. If it is taken in the first way, then it is true that each thing is more inclined toward what belongs to it from itself than toward what belongs to it from another alone. But then it is false that the nature of a possible thing has non-being from itself, according to the mind of Saint Thomas. — If, however, it is taken in the second way, then it is true that the nature of a possible thing has non-being from itself. And this is how Saint Thomas understands it. But then the consequence is denied. And in proof of it, the assumption is denied. Therefore, since a possible thing, insofar as it is such, does not have esse from itself, and yet receiving esse is not repugnant to it, it is equally disposed to esse and non-esse: that is, it can have non-esse just as it can have esse, and conversely.

Aureol considers this argument ineffective among the philosophers, judging that they would not concede any necessary thing that has a productive cause. But there will be a special inquiry into this below ⁶.

VI. Fifth, an argument is made on Aristotle’s authority in Book VIII of the Physics. Time is eternal. Therefore motion is eternal. Therefore the mover is eternal. But the first moving substance is God. Therefore, etc.

But if the antecedent is denied, the intended conclusion follows even from its opposite. For if motion and time began, then they began from some mover. But there is no regress to infinity. Therefore one arrives at something that did not begin, and consequently is eternal.

Finally, the authority of Sacred Scripture favors this truth. For it is said in Psalm 101: But you, Lord, endure forever. Likewise: But you are the selfsame, and your years shall not fail.

VII. For the clarification of what is said here, it must be considered that, although duration seems to involve a certain distension, succession, and a before and after, and even to measure really the things that fall under duration—because these are found in that duration more known to us, namely time—nevertheless there are found certain durations which have neither extension nor succession but consist in something indivisible, such as eternity and the aevum; just as those things which endure under them are indivisible. Nor does eternity really measure the divine esse, as though it were something really distinct from God, better known and more manifest than He is: rather it is a measure only according to our manner of understanding, as was shown above ⁷