The Divine Lamp

Chapter 15
That God Is Eternal.

I. From the foregoing it is also clear that God is eternal.

II. For whatever begins or ceases to be, suffers this through movement or change. Now it has been shown (in ch. 13) that God is altogether unchangeable. Therefore He is eternal, having neither beginning or end.

III. Again. Only things which are moved are measured by time: because time is the measure of movement, as stated in Physics 4., 11 [219b, 1] Now God is absolutely without movement, as we have already proved (in ch. 11). Therefore we cannot mark before and after in Him. Therefore in Him there is not being after non-being, nor can He have non-being after being, nor is it possible to find any succession in His being, because these things cannot be understood apart from time. Therefore He is without beginning and end, and has all His being simultaneously: and in this consists the notion of eternity (see ST I., Q 10).

IV. Moreover. If any time He was not and afterwards was, He was brought by someone out of non-being into being. Not by Himself; because what is not cannot do anything. And if by another, this other is prior to Him. Now it has been shown (ch. 13) that God is the first cause. Therefore He did not begin to be. Therefore neither will He cease to be: because that which always was, has the power to be always. Therefore He is eternal.

V. Furthermore. We observe that in the world there are certain things which can be and not be, namely those that are subject to generation and corruption. Now whatsoever is possible to be has a cause, because, as in itself it is equally related to two things, namely being and not being, it follows that if it acquires being this is the result of some cause. But as proved above ((ch. 13) by Aristotle’s argument, we cannot go on to infinity in causes. Therefore we must suppose some thing, which is necessary to be. Now every necessary thing either has a cause of its necessity from without, or has no such cause, but is necessary of itself. But we cannot go on to infinity in necessary things that have causes of their necessity from without. Therefore we must suppose some first necessary thing which is necessary of itself: and this is God, since He is the first cause, as proved above (Ch. 13). Therefore God is eternal, since whatever is necessary of itself is eternal.

VI. Again. Aristotle (Physics 8, 1 [251b 12]) proves the everlastingness of movement from the everlastingness of time: and thence he goes on to prove the everlastingness of the substance that is the cause of movement Physics 8, 6 [258b 13]. Now the first moving substance is God. Therefore He is everlasting. And supposing the everlastingness of time and movement to be denied, there still remains the argument in proof of the everlastingness of substance. For if the movement had a beginning, it must have had its beginning from some agent. And thus either we shall go on to infinity, or we shall come to something without a beginning.

VII. Divine authority bears witness to this truth: wherefore the Psalm reads: But Thou, O Lord, endurest for ever Ps 101: 13), and again: But Thou art always the self-same, and Thy years shall not fail (Ps 101: 28).

Chapter 14
That In Order To Acquire Knowledge Of God It Is Necessary To Proceed By The Way Of Remotion.

I. Accordingly having proven that there is a first being which we call God, it behooves us to inquire into His Nature.

II. Now in treating of the divine essence the principle method to be followed is that of remotion.  For the divine essence by its immensity surpasses every form to which our intellect reaches; and thus we cannot apprehend it by knowing what it is.  But we have some knowledge thereof according as we shall be enabled to remove by our intellect a greater number of things therefrom.  For the more completely we wee how a thing differs from others, the more perfectly we know it: since each thing has has in itself its own being distinct from all other things.  Wherefore when we know the definition of a thing, first we place it in a genus, whereby we know in general what it is, and afterwards we add differences, so as to mark its distinction from other things: and thus we arrive at the complete knowledge of a thing’s essence.

III. Since, however, we are unable in treating of the divine essence to take what as a genus, nor can we express its distinction from other things by affirmative differences, we must needs express it by negative differences.  Now just as in affirmative differences one restricts another, and brings us the nearer to a complete description of the thing, according as it makes it to differ from more things, so one negative difference is restricted by another that marks a distinction from more things.  Thus, if we say that God is not an accident, we thereby distinguish Him from all accidents; then if we add that He is not a body, we shall distinguish Him also from certain substances, and thus in gradation He will be differentiated by suchlike negations from all besides Himself: and then when He is known as distinct from all things, we shall arrive at a proper consideration of Him.  It will not, however, be perfect, because we shall not know what He is in Himself.

IV. Wherefore in order to proceed about the knowledge of God by the way of remotion, let us take as principle that which is already made manifest by what we have said above (Ch. 13) , namely that  God is altogether unchangeable.  This is also confirmed by the authority of Holy Writ.  For it is said (Mal 3:6) I am God (Vulgate: Lord) and I change not. (James 1:17) With Whom there is no change; and Numbers (23:19) God is not as a man…that He should be changed.

In chapter 10 of the SCG St Thomas presented the opinion of those who held that the existence of God could not be demonstrated, being self-evident. These opinions were answered by Aquinas in chapter 11. In chapter 12 he presented and responded to those who held that the existence of God could only be known by the light of faith and, as a consequence, could not be demonstrated. Here in chapter 13 he presents his demonstrations in proof of God’s existence. The presentation here is significantly longer and more detailed than that found in the Summa of Theology, Article 2. I originally posted this chapter in three posts but now consolidate them here.

Chapter 13
Part 1
Demonstrations in Proof of the Existence of God

I. Having shown then that it is not futile to endeavor to prove the existence of God, we may proceed to set forth the reasons whereby both philosophers and Catholic doctors have proved that there is a God.

II. In the first place we shall give the arguments by which Aristotle sets out to prove God’s existence: and he aims at proving this from the point of view of movement, in two ways.

III. The first way is as follows (Physics VII. 1. Whatever is in motion is moved by another: and it is clear to the sense that something, the sun for instance, is in motion. Therefore it is set in motion by something else moving it. Now that which moves it is itself either moved or not. If it be not moved, then the point is proved that we must needs postulate an immovable mover: and this we call God. If, however, it be moved, it is moved by another mover. Either, therefore, we must proceed to infinity, or we must come to an immovable mover. But it is not possible to proceed to infinity. Therefore it is necessary to postulate an immovable mover. Aquinas lacked our advanced scientific knowledge and believed that the sun revolved around the earth. As Peter Kreeft rightly notes however, “the invalid illustration does not invalidate the principle” (SUMMA OF THE SUMMA, footnote 28, pg. 69). Incidentally, Aquinas correctly held with most medievals that the earth was round (ST. I. Q. 1, art. 1).

IV. This argument contains two propositions that need to be proved: namely that whatever is in motion is moved by another, and that it is not possible to proceed to infinity in movers and things moved.

V. The first of these is proved by the Philosopher in three ways. First, thus. If a thing moves itself, it must needs have the principle of its movement in itself, else it would clearly be moved by another. Again it must be moved primarily, that is, it must be moved by reason of itself and not by reason of its part, as an animal is moved by the movement of its foot, for in the latter way not the whole but the part would be moved by itself, and one part by another. Again it must be divisible and have parts, since whatever is moved is divisible, as is proved in Physics VI, 4.

VI. These things being supposed, he argues as follows. That which is stated to be moved by itself is move primarily. Therefore if one of its parts is at rest, it follows that the whole is at rest. For if, while one part is at rest, another of its parts were in motion, the whole itself would not be moved primarily, but its part which is in motion while another is at rest. Now nothing that is at rest while another is at rest, is moved by itself: for that which is at rest as a result of another thing being at rest must needs be in motion as a result of the other’s motion, and hence it is not moved by itself. Therefore whatever is in motion needs to be moved by another.

VII. Nor it this argument traversed by the statement that might be made, that supposing a thing moves itself, it is impossible for a part thereof to be at rest, or again by the statement that to be at rest or in motion does not belong to a part except accidentally, as Avicenna quibbles (Sufficientia II, 1). Because the force of the argument lies in this, that if a thing moves itself primarily and of itself, not by reason of its parts, it follows that its being moved does not depend on some thing; whereas with a divisible thing, being moved, like being, depends on its parts, so that it cannot move itself primarily and of itself. Therefore the truth of the conclusion drawn does not require that we suppose as an absolute truth that a part of that which moves itself is are rest, but that this conditional statement be true that if a part were at rest, the whole would be at rest. Whcih statement can be true even if the antecedent be false, even as this conditional proposition is true: If a man is an ass he is irrational.

VIII. Secondly, he proves it by induction, thus Physics VIII, 4. A thing is not moved by itself if it is moved accidentally, since its motion is occasioned by the motion of something else. Nor again if it is moved by force, as is manifest. Nor if it is moved by its nature, as heavy and light things are, since these are moved by their generating cause and by that which removes obstacles the to the movement. Now whatever things are in motion are moved either per se or accidentally; and if per se, either by force or by nature: and if the latter, either by something in them, as in the case of animals, or not by something in them, as in the case of heavy and light bodies. Therefore whatever is in motion is moved by another.

IX. Thirdly, he proves his point thus (Physics VIII, 5). Nothing is at the same time in act and in potentiality in respect of the same thing. Now whatever is in motion, as such, is in potentiality, because motion is the act of that which is in potentiality, as such (Physics III, 1). Whereas whatever moves, as such, is in act, for nothing acts except in so far as it is in act. Therefore nothing is both mover and moved in respect of the same movement. Hence nothing moves itself.

X. We must observe, however, that Plato, who asserted that every mover is moved (Phaedrus p. 247c), employed the term movement in a more general sense that Aristotle. For Aristotle took movement in its strict sense, for the act of a thing that is in potentiality as such, in which sense it applies only to divisible things and bodies, as is proved in Physics VI, 4. Whereas according to Plato that which moves itself is not a body; fo rhe took movement for any operation, so that to understand or to think is a kind of movement, to which manner of speaking Aristotle alludes in De Anima III, 7. In this sense, then, he said that the first mover moves itself, in as much as it understands, desires and loves itself. This, in a certain respect, is not in contradiction with the arguments of Aristotle; for it makes no difference whether with Plato we come to a first mover that moves itself, or with Aristotle to something first which is altogether immovable.

XI. He proves the other proposition, namely that it is impossible to proceed to infinity in movers and things moved, by three arguments.

XII. The first of these is as follows (Physics VII, 1). If one were to proceed to infinity in movers and things moved, all this infinite number of things would necessarily be bodies, since whatever is moved is divisible and corporeal, as is proved in Physics VI, 4. Now every body that moves through being moved is moved at the same time as it moves. Therefore all this infinite number of things are moved in a finite time. But this is impossible. Therefore it is impossible to proceed to infinity in movers and things moved.

XIII. That it is impossible for the aforesaid infinite number of things to be moved in a finite time, he proves thus. Mover and moved must needs be simultaneous; and he proves this by induction from each species of movement. but bodies cannot be simultaneous except by continuity or contact. Wherefore since all the aforesaid movers and things moved are bodies, as proved, they must needs be as one movable thing through their continuity or contact. And thus one infinite thing would be move in a finite time, which is shown to be impossible in Physics VII, 1.

XIV. The second argument in proof of the same statement is as follows Physics VIII, 5. In an inordinate series of movers and things moved, where namely throughout the series one is moved by the other, we must needs find that if the first mover be taken away or cease to move, none of the others will move or be moved: because the first is the cause of movement in all the others. Now if an ordinate series of movers and things moved proceed to infinity, there will be no first mover, but all will be intermediate movers as it were. Therefore it will be impossible for any of them to be moved: and thus nothing in the world will be moved.

XV. The third argument amount to the same, except that it proceeds in the reverse order, namely by beginning from above: and it is as follows. That which moves instrumentally, cannot move unless there be something that moves principally. But if we proceed to infinity in movers and things moved, they will all be like instrumental movers, because they will be alleged to be moved movers, and there will be nothing by way of principal mover. Therefore nothing will be moved.

XVI. We have thus clearly proved both statements which were supposed in the first process of demonstration whereby Aristotle Proved the existence of a first immovable mover.

XVII. The second way is as follows. If every mover is moved, this statement is true either in itself or accidentally. If accidentally, it follows that it is not necessary: for that which is accidentally true is not necessary. Therefore it is a contingent proposition that no mover is moved. But if a mover be moved, it does not move, as the opponent asserts. Therefore it is contingent that nothing is moved, since, if nothing moves, nothing is moved. Now Aristotle holds this to be impossible, namely, that at any time there be no movement (Physics VIII, 5). Therefore the first proposition was not contingent, because a false impossibility does not follow from a false contingency. And therefore this proposition, Every mover is moved by another, was not accidentally true.

XVIII. Again, if any two things are found accidentally united in a certain subject, and one of them is to be found without the other, it is probable that the latter can be found without the former: thus if white and musical are found in Socrates, and musical without white is found in Plato, it is probable that it is possible to find white without musical in some subject. Accordingly if mover and moved be united together in some subject accidentally, and it be found that a certain thing is moved without its being a mover, it is probable that a mover is to be found that is not moved. Nor can one urge against this the case of two things one of which depends on the other; because those in question are united not per se but accidentally.

XIX. If, however, the aforesaid proposition is true in itself, again there follows something impossible and unfitting. For the mover must needs be moved either by the same kind of movement or by another kind. If by the same kind, it follows that whatever causes alteration must itself be altered, and furthermore that the healer must be healed, that the teacher must be taught, and in respect of the same science. But this is impossible: for the teacher must needs have science, while the learner must needs not have it, and thus the same will be both possessed and not possessed by the same, which is impossible. And if it be moved by another kind of movement, so that, to wit, that which moves in respect of place be increased, and so on, it will follow that we cannot go on indefinitely, since the genera and species of movement are finite in number. And thus there will be some first mover that is not moved by another. Unless, perchance, someone say that a recurrence takes place, in this way, that when all the genera and species of movement have been exhausted, a return must be made to the first; for instance, if that which moves in respect of place be altered, and that which causes alteration be increased, then again that which is increased be moved in respect of place. But the consequence of this will be the same as before; namely, that which moves by one kind of movement is itself moved by the same kind, not imimmediately indeed but mediately.

XX. It remains therefore that we must needs postulate some first mover that is not moved by anything outside itself.

XXI. Since however, given that there is a first mover that is not moved by anything outside itself, it does not follow that it is absolutely immovable, Aristotle proceeds further, saying that this may happen in two ways (Physics VIII, 5). First, so that this first mover is absolutely immovable. And if this be granted, our point is established, namely that there is a first immovable mover. Secondly, that this first mover is moved by itself. And this seems probable: because what is of itself is always prior to what is of another: wherefore also in things moved, it is logical that what is moved first is moved by itself and not another.

XXII. But if this be granted, the same consequence follows (Physics VIII, 5). For it cannot be said that the whole of that which moves itself is moved by its whole self, because then the absurd consequences mentioned above would follow, namely that a person might teach and be taught at the same time, and in like manner as to other kinds of movement; and again that a thing would be at the same time in act and in potentiality, since a mover, as such, is in act, while that which is moved is in potentiality. It remains, therefore, that one part thereof is mover only, and the other part moved. And thus we have the same conclusion as before, namely that there is something that moves and is itself immovable.

XXIII. And it cannot be said that both parts are moved, so that one is moved by the other; nor that one part moves both itself and the other; nor that the whole moves a part; nor that part moves the whole, since the above absurdities would follow, namely that something would both move and be moved by the same kind of movement, and that it would be at the same time in potentiality and in act, and moreover that the whole would move itself not primarily but by reason of its part. It remains, therefore, that in that which moves itself, one part must be immovable, and must move the other part.

XXIV. Since, however, in those things among us which move themselves, namely animals, the part which moves, namely the soul, though immovable by itself, is nevertheless moved accidentally, he goes on to show that in the first mover, the part which moves is not moved neither of itself nor accidentally (Physics VIII, 6).

For in those things which among us move themselves, namely animals, since they are coruuptible, the part which moves is moved accidentally. Now those corruptible things which move themselves must needs be reducible to some first self-mover that is everlasting. Therefore that which moves itself must have a mover, which is moved neither of itself nor accidentally.

XXV. It is clear that, in accordance with his hypothesis, some self-mover must be everlasting. For it, as he supposes, movement is everlasting, the production of these self-movers that are subjects to generation and corruption must be everlasting. But no one of these self-movers, since it does not always exist, can be the cause of this everlastingness. Nor can all of them together, because they would be infinite, and because they do not exist all together. It follows therefore that there must be an everlasting self-mover, that causes the everlastingness of generation in these lower self-movers. And thus its mover is not moved, neither of itself nor accidentally.

XXVI. Again, we observe that in self-movers some begin to be moved anew on account of some movement whereby the animal is not moved by itself, for instance by the digestion of food or a change in the atmosphere: by which movement the mover that moves itself is moved accidentally. Whence we may gather that no self-mover, whose mover is moved per se or accidentally, is always moved. But the first self mover is always in motion, else movement could not be everlasting, since every other movement is caused by the movement of the first self-mover. It follows therefore that the first self-mover is moved by a mover who is not moved, neither per se nor accidentally.

XXVII. Nor is this argument rebutted by the fact that the movers of the lower spheres cause an everlasting movement, and yet are said to be moved accidentally. For they are said to be moved accidentally not by reason of themselves, but by reason of the things subject to their motion, which follow the motion of the higher sphere.

XXVIII. Since, however, God is not part of a self-mover, Aristotle goes on in his Metaphysics XII, 7 to trace from this motor that is part of a self-mover, another mover altogether separate, which is God. For since every self-mover is moved through its appetite, it follows that the motor that is part of a self-mover, moves on account of the appetite for some appetible object. And this object is above the motor in moving, because the appetible is a moved mover, whereas the appetible is a mover altogether unmoved. Therefore there must needs be a first mover separate and altogether immovable, and this is God.

XXIX. Now two things would seem to weaken the above arguments. The first of these is that they proceed from the supposition of the eternity of movement, and among Catholics this is supposed to be false.

XXX. To this we reply that the most effective way to prove God’s existence is from the supposition of the eternity of the world, which being supposed, it seems less manifest that God exists. For if the world and movement had a beginning, it is clear that we must suppose some cause to have produced the world and movement, because whatever becomes anew must take it origin from some cause of its becoming, since nothing evolves itself from potentiality to act, or from non-being to being.

XXXI. The second is that the aforesaid arguments suppose that the first moved thing, namely the heavenly body, has its motive principle in itself, whence it follows that it is animated: and by many this is not granted.

XXXII. To this we reply that if the first mover is not supposed to have its motive principle in itself, if follows that it is immediately moved by something altogether immovable. Hence also Aristotle draws this conclusion with an alternative, namely that either we must come at once to a first mover immovable and separate, or to a self-mover from which again we come to a first mover immovable and separate (Physics VIII, 5).

XXXIII. The Philosopher proceeds in a different way in Metaphysics to show that it is impossible to proceed to infinity in efficient causes, and that we must come to one first cause, and this we call God (Metaphysics Ia, 2). This is how he proceeds. In all efficient causes following in order, the first is the cause of the intermediate cause, and the intermediate cause is the cause of the ultimate, whether the intermediate be one or several. Now if the cause be removed, that which it cases is removed. Therefore if we remove the first the intermediate cannot be a cause. But if we go on to infinity in efficient causes, no cause will be first. Therefore all the others which are intermediate will be removed. Now this is clearly false. Therefore we must suppose the existence of a first efficient cause: and this is God.

XXXIV. Another reason can be drawn from the words of Aristotle. For in Metaphysics Ia, 1 he shows that there is something supremely true, from the fact that we see that of two false things one is falser that the other, wherefore it follows that one also is truer than the other (Metaphysics IV, 4). Now this is by reason of approximation to that which is simply and supremely true. Wherefore we may further conclude that there is something that is supremely being. And this we call God.

XXXV. Another argument in support of this conclusion is adduced by Damascene from the government of things (De Fide Orthodoxa I, 3): and the same reasoning is indicated by the Commentator (Averroes) in Physics 2 (i.e., In II Physicorum, t.c. 75). It runs as follows. It is impossible for contrary and discordant things to accord in one order always or frequently except by someone’s governance, whereby each and all are made to tend to a definite end. Now we see that in the world of things of different natures accord in one order, not seldom and fortuitously, but always or for the most part. Therefore it follows that there is someone by whose providence the world is governed. And this we call God.

Text in red are my notations.

Chapter 12

Concerning The Opinion Of Those Who Say That The Existence Of God Cannot Be Proved, And That It Is Held By Faith Alone.

In chapter 10 the Saint presented the opinion of those who held that the existence of God was self-evident, and responded to those arguments in chapter 11. Here, as the title indicates, he is presenting (and responding to) the position of those who eschew reason in relation to the question can the existence of God be demonstrated? In chapter 13 he will give his famous “arguments in proof of God’s existence.”

The term quiddity is defined as follows: Quiddity = a synonym of essences by which one answers the question about a thing, “what is it?” (Quidditas = synonymum essentiae, quo respondetur quaestioni super rem “quid est ?’ SOURCE,see #95)

The Position that we have taken is also assailed by the opinion of certain others, whereby the efforts of those who endeavor to prove that there is a God would again be rendered futile. For they say that it is impossible by means of the reason to discover that God exists, and that this knowledge is acquired solely by means of faith and revelation. (St Thomas also deals with this issue in the ST. I, 2. This was the position of Moses Maimonides)

In making this assertion some were moved by the weakness of the arguments which certain people employed to prove the existence of God.

Possibly, however, this error might falsely seek support from the statements of certain philosophers, who show that in God essence and existence are the same, namely that which answers to the question, What is He? and that which answers to the question, Is He? Now it is impossible by the process of reason to acquire the knowledge of what God is. Wherefore seemingly neither is it possible to prove by reason whether God is.

Again. If, as required by the system of the Philosopher (Posterior Analytics II,9. 93b, 22), in order to prove whether a thing is we must take as principle the signification of its name, and since according to the Philosopher (4 Metaph IV, 7, This link is to Thomas’ commentary on Metaphysics, Lecture 16. see #391 and Thomas’ note at #733) the signification of a name is its definition: there will remain no means of proving the existence of God, seeing that we lack knowledge of the divine essence or quiddity.

Again. If the principles of demonstration becomes known to us originally through the senses, as is proved in the Posterior Analytics (I. 18 see footnote 1 below) , those things which transcend all sense and sensible objects are seemingly indemonstrable. Now such is the existence of God. Therefore it cannot be demonstrated.

The falseness of this opinion is shown to us first by the art of demonstration, which teaches us to conclude causes from effects. Secondly, by the order itself of sciences: for if no substance above sensible substances can be an object of science, there will be son science above Physics,, as stated in 4 Metaphysics (See book 4, chap. 2). Thirdly, by the effects of the philosophers who have endeavored to prove the existence of God. Fourthly, by the apostolic truth which asserts (Rom 1:20) that the invisible things of God are clearly seen, being understood by the things that are made.

Nor should we be moved by the consideration that in God essence and existence are the same, as the first argument contended. For this is to be understood of the existence by which God Subsists in Himself, of which we are ignorant as to what kind of a thing it is, even as we are ignorant as to what kind of a thing it is, even as we are ignorant of His essence. But it is not to be understood of that existence which is signified by the composition of the mind. For in this way it is possible to prove the existence of God, when our mind is led by demonstrative arguments to form a proposition stating that God is.

Moreover. In those arguments whereby we prove the existence of God, it is not necessary that the divine essence or quiddity be employed as the middle term, as the second argument supposed: but instead of the quiddity we take His effects as the middle term, as is the case in a posteriori reasoning: and from these effects we take the signification of this word God. For all the divine names are taken either from the remoteness of god’s effects from Himself, or from some relationship between god and His effects.

I tis also evident from the fact that, although God transcends all sensibles and sensed, His effects from which we take the proof that God exists, are sensible objects. Hence our knowledge, even of things which transcend the senses, originates from the senses.

Footnotes:

It is also clear that the loss of any one of the senses entails the loss of a corresponding portion of knowledge, and that, since we learn either by induction or by demonstration, this knowledge cannot be acquired. Thus demonstration develops from universals, induction from particulars; but since it is possible to familiarize the pupil with even the so-called mathematical abstractions only through induction-i.e. only because each subject genus possesses, in virtue of a determinate mathematical character, certain properties which can be treated as separate even though they do not exist in isolation-it is consequently impossible to come to grasp universals except through induction. But induction is impossible for those who have not sense-perception. For it is sense-perception alone which is adequate for grasping the particulars: they cannot be objects of scientific knowledge, because neither can universals give us knowledge of them without induction, nor can we get it through induction without sense-perception. (Source. Some copyright laws apply, see HERE).

Chapter 11

Refutation Of The Foregoing Opinion And Solution Of The Aforesaid Arguments.

St Thomas is here responding to the arguement presented in the last chapter.

The foregoing opinion arose from their being accustomed from the beginning to hear and call upon the name of God.  Now custom, especially if it date from  our childhood, acquires the force of nature, the result being that the mind holds those things with which it was imbued from childhood as firmly as though they were self-evident.  It is also a result of failing to distinguish between what is self-evident simply, and that which is self-evident to us.  For it is simply self-evident that God is, because the selfsame thing which God is, is His existence.  But since we are unable to conceive mentally the selfsame thing which is God, that thing remains unknown in regard to us.  Thus it is self-evident simply that every whole is greater than its parts, but to the one who fails to conceive mentally the meaning of a whole, it must needs be unknown.  Hence it is that those things which are most evident of all are to the intellect what the sun is to the eye of an owl, as stated in Metaphysics ii.

Nor does it follow, as the first argument alleged, that as soon as the meaning of the word God is understood, it is known that God is.  First, because it is not known to all, even to those who grant that there is a God, that God is that thing than which no greater can be thought of, since many of the ancients asserted that this world is God.  Nor can any such conclusion be gathered from the significations which Damascene assigns to this word God (De Fid. Orth. Bk. 1, Ch 1. See quote below).  Secondly because, granted that everyone understands this word God to signify something than which a greater cannot be thought of, it does not follow that something than which a greater cannot be thought of exists in reality.  For we must needs allege a thing in the same way as we allege the signification of its name.  Now from the fact that we conceive mentally that which the word God is intended to convey, it does not follow that God is otherwise than in the mind.  Wherefore neither will it follow that the thing than which a greater cannot be thought of is otherwise than in the mind.  And thence it does not follow that there exists in reality something than which a greater cannot be thought of .  Hence this is no argument against those who assert that there is no God, since whatever be granted to exist, whether in reality or in the mind, there is nothing to prevent a person from thinking of something greater, unless he grants that there is in reality something than which a greater cannot be thought of.

Again it does not follow, as the second argument pretended, that if it is possible to think God is not, it is possible to think of something greater than God.  For that it be possible to think that He is not, is not on account of the imperfection of His being or the uncertainty thereof, since in itself His being is supremely manifest, but is the result of the weakness of our mind which is able to see Him, not in Himself but in His effects, so that it is led by reasoning to know that He is.

Wherefore the third argument also is solved.  For just as it is self-evident to us that a whole is greater than its parts, so is it most evident to those who see the very  essence of God that God exists, since His essence is His existence.  But because we are unable to see His essence, we come to know His existence not in Himself but in His effects.

The solution to the fourth argument is also clear.  For man know God naturally in the same way he desires Him naturally.  Now a man desires Him naturally in so far as he naturally desires happiness, which is a likeness of the divine goodness.  Hence it does not follow that God considered in Himself is naturally known to man, but that His likeness is.  Wherefore man must needs come by reasoning to know God in the likeness to Him which he discovers in God’s effects.

It is also easy to reply to the fifth argument.  For God is that in which all things are known, not so that other things be unknown except He be known, as happens in self-evident principles, but because all knowledge is caused in us by His outpouring.

St John Damascene:

No one hath seen God at any time; the Only-begotten Son, which is in the bosom of the Father, He hath declared Him(1). The Deity, therefore, is ineffable and incomprehensible. For no one knoweth the Father, save the Son, nor the Son, save the Father(2). And the Holy Spirit, too, so knows the things of God as the spirit of the man knows the things that are in him(3). Moreover, after the first and blessed nature no one, not of men only, but even of supramundane powers, and the Cherubim, I say, and Seraphim themselves, has ever known God, save he to whom He revealed Himself.

God, however, did not leave us in absolute ignorance. For the knowledge of God’s existence has been implanted by Him in all by nature. This creation, too, and its maintenance, and its government, proclaim the majesty of the Divine nature(4). Moreover, by the Law and the Prophets(5) in former times and afterwards by His Only-begotten Son, our Lord and God and Saviour Jesus Christ, He disclosed to us the knowledge of Himself as that was possible for us. All things, therefore, that have been delivered to us by Law and Prophets and Apostles and Evangelists we receive, and know, and honour(6), seeking for nothing beyond these. For God, being good, is the cause of all good, subject neither to envy nor to any passion(7). For envy is far removed from the Divine nature, which is both passionless and only good. As knowing all things, therefore, and providing for what is profitable for each, He revealed that which it was to our profit to know; but what we were unable(8) to bear He kept secret. With these things let us be satisfied, and let us abide by them, not removing everlasting boundaries, nor overpassing the divine tradition(9).

For more on this topic:

See Chapter two of THE ONE GOD: A Commentary On The First Part Of St Thomas’ Theological Summa, by Reginald Garrigou-Lagrange

What follows is an excerpt from MORAL PHILOSOPHY, by Joseph Rickaby.  Links and text in red represent my additions.  The sole purpose of the first chapter is to summarize certain introductory points.

Of The Object-Matter And Partition Of Moral Philosophy.

1. Moral Philosophy is the science that considers human acts inasmuch as they befit man’s rational nature and make towards man’s last end. Philosophy means the love (philia) of wisdom (sophia). Wisdom orders things to an end: “Accordingly it is proper to moral philosophy, to which our attention is at present directed, to consider human operations insofar as they are ordered one to another and to an end” (Aristotle) The last end of man is happiness: “Final and perfect happiness can consist in nothing else than the vision of the Divine Essence” (Aquinas). For more on wisdom and the science of Philosophy in general read chapter 1 of the Summa Contra Gentiles. For more on happiness (Beatific Vision) see SCG, Bk. 3, Ch. 37.

2. Those acts alone are properly called human, which a man is master of to do or not to do. A human act, then, is an act voluntary and free. A man is what his human acts make him. Concerning this, read this excerpt from Walter Farrell’s Companion To The Summa, Bk. 2, Ch. 2. Also, read the Summa Theologica Ia-IIae, Q. 1, Art. 1.

3. A voluntary act is an act that proceeds from the will with a knowledge of the end to which the act tends. See ST. Ia-IIae, Q. 6, Art. 1.

4. A free act is an act which proceeds from the will that under the same antecedent conditions it might not have proceeded. See ST. Ia-IIae, Q. 13, Art. 6.

5. Human acts, as defined above, are the subject-matter of moral philosophy. The special light in which it considers them is their agreement with, or opposition to, man’s rational nature. That agreement or opposition is their moral good or evil, and is called morality. See ST. Ia-IIae, Q. 18, Arts. 1-11.

6. Moral Philosophy is divided into Ethics and Natural Law. The principal business of Ethics is to determine what moral obligation is, or to fix what logicians call the comprehension of the idea I ought. It belongs to Natural Law to consider what things are morally obligatory, or to determine the extension of the idea I ought.

7. Ethics stand to Natural Law as Pure Mathematics to Mixed.

Chapter 10 Of the opinion of those who aver that it cannot be demonstrated that there is a God, since this is self-evident. (The arguments presented here will be refuted in chapter 11).

Possibly it will seem to some that it is useless to endeavor to show that there is a God: they say that it is self-evident that God is, so that it is impossible to think the contrary, and thus it cannot be demonstrated that there is a God.  The reasons for this view are as follows.  Those things are said to be self-evident which are known as soon as the terms are known: thus as soon as it is known what is a whole, and what is a part, it is known that the whole is greater than its parts.  Now such is the statement “God is.”  For by this word “God” we understand a thing a greater  than which cannot be thought of: this is what a man conceives in his mind when he hears and understands this word “God”: so that God must already be at least in his mind.  Nor can He be in the mind alone, for that which is both in the mind and in reality is greater than that which is in the mind only.  And the very signification of the word shows that nothing is greater than God.  Wherefore it follows that it is self-evident that God is, since it is made clear from the very signification of the word.

Again.  It is possible to think that there is a thing which cannot be thought not to exist: and such a thing is evidently greater than that which can be thought not to exist.  Therefore if God can be thought not to exist, it follows that something can be thought greater than God: and this is contrary to the signification of the term.  Therefore it remains remains that it is self-evident that God is.

Further.  Those propositions are most evident in which the selfsame thing is predicated of itself, for instance: Man is man; or wherein the predicate is included in the definition of the subject, for instance: Man is an animal.  Now, as we shall show further on (chapt 22), in God alone do we find that His being is His essence, as though the same were the answer to the question, What is He? as to the question, Is He? Accordingly when we say, God is, the predicate is either identified with the subject, or at least is included in the definition of the subject.  And thus it will be self-evident that God is.

Moreover.  Things that are known naturally are self-evident, for it is not by a process of research that they become evident.  Now it is naturally known that God is, since man’s desire tends naturally to God as his last end, as we shall show further on (book 3, chapt 25).  Therefore it is self-evident that God is.

Again.  That whereby all things are known must needs be self-evident.  Now such is God.  For just as the light of the sun is the principle of all visual perception, so the divine light is the principle of all intellectual knowledge, because it is therein that first and foremost intellectual light is to be found.  Therefore it must needs be self-evident that God is, that it is impossible for the mind to think the contrary.

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Now though the aforesaid truth of the Christian faith surpasses the ability of human reason, nevertheless those things which are naturally instilled in human reason cannot be opposed to this truth. For it is clear that those things which are implanted in reason by nature, are most true, so much so that it is impossible to think them to be false. Nor is it lawful to deem false that which is held by faith, since it is so evidently confirmed by God. See then that the false alone is opposed to the true, as evidently appears if we examine their definitions, it is impossible for the aforesaid truth of faith to be contrary to those principles which reason knows naturally.

Again. The same thing which the disciple’s mind receives from its teacher is contained in the knowledge of the teacher, unless he teach insincerely, which it were wicked to say of God. Now the knowledge of naturally known principles is instilled into us by God, since God himself is the author of our nature. Therefore the divine Wisdom also contains these principles. Consequently whatever is contrary to these principles, is contrary to the divine Wisdom; wherefore it cannot be from God. Therefore those things which are received by faith from divine revelation cannot be contrary to our natural knowledge.

Moreover. Our intellect is stayed by contrary arguments, so that it cannot advance to the knowledge of truth. Wherefore if conflicting knowledge were instilled into us by God, our intellect would thereby be hindered from knowing the truth. And this cannot be ascribed to God.

Furthermore. Things that are natural are unchangeable so long as nature remains. Now contrary opinions cannot be together in the same subject. Therefore God does not instill into man any opinion or belief contrary to natural knowledge.

Hence the Apostle says (Rom 10:8) The word is nigh thee even in thy heart and in thy mouth. This is the word of faith which we preach. Yet because it surpasses reason some look upon it as though it were contrary thereto; which is impossible.

This is confirmed also by the authority of Augustine who says (Gen. ad. lit. ii) That which truth shall make known can nowise be in opposition to the holy books whether of the Old or of the New Testament.

From this we may evidently conclude that whatever arguments are alleged against the teachings of aith, they do not rightly proceed from the first self-evident principles instilled by nature. Wherefore they lack the force of demonstration, and are either probable or sophistical arguments, and consequently it is possible to solve them.

Further reading:

On Faith and Reason Pope Benedict XVI

The Renaissance of Faith and Reason Robert P. George

Study Notes on Faith and Reason Alfred J. Freddoso

Fides et Ratios: A Radical Vision on Intellectual Inquiry Alfred J. Freddoso

That It Is not A Mark Of Levity To Assent To The Things That Are Of Faith, Although They Are Above Reason.

Now those who believe this truth, of which reason affords a proof, believe not lightly, as though following foolish fables (2 Pet 1:16).  For Divine Wisdom Himself, Who knows all things most fully, deigned to reveal to man the secrets of God’s wisdom: and by suitable arguments proves His presence, and the truth of His doctrine and inspiration, by performing works surpassing the capability of the whole of nature, namely, the wondrous healing of the sick, the raising of the dead to life, a marvellous control over the heavenly bodies, and what excites yet more wonder, the inspiration of human minds, so that unlettered and simple persons are filled with the Holy Ghost, and in one instant are endowed with the most sublime wisdom and eloquence.  And after considering these arguments, convinced by the strength of the proof, and not by force of arms, not by the promise of delights, but-and this is the greatest marvel of all-amidst the tyranny of persecutions, a countless crowd of not only simple but also of the wisest men, embraced the Christian faith, which inculcates things surpassing all human understanding, curbs the pleasures of the flesh, and teaches contempt of all worldly things.  That the minds of mortal beings should assent to such things, is both the greatest of miracles, and the evident work of divine inspiration, seeing that they despise visible things and desire only those that are invisible.  And that this happened not suddenly nor by chance, but by the disposition of God, is shown by the fact that God foretold that He would do so by the manifold oracles of the prophets, whose books we hold in veneration as bearing witness to our faith.  This particular kind of proof is alluded to in the words of Heb 2:3-4 Which namely, the salvation of mankind, having begun to be declared by the Lord, was confirmed with us by them that heard Him, God also bearing witness by signs and wonders, and diverse miracles and distributions of the Holy Ghost.  

Now such a wondrous conversion of the world to the Christian faith is a most indubitable proof that such signs did take place, so that there is no need to repeat them, seeing that there is evidence of them in their result.  For it would be the most wondrous sign of all if without any wondrous signs the world were persuaded by simple and lowly men to believe things so arduous, to accomplish things so difficult, and to hope for things so sublime.  Although God ceases not even in our time to work miracles through His saints in confirmation of the faith.

On the other hand those who introduced the errors of the sects proceeded in contrary fashion, as instanced by Mahammed, who enticed peoples with the promise of carnal pleasures, to the desire of which the concupiscence of the flesh instigates.  he also delivered commandments in keeping with his  promises, by giving the  reins to  carnal pleasure, wherein it is easy for carnal men to obey: and the lessons of truth which he  inculcated were only such as can be easily known to any man of average wisdom by his natural powers: yea rather the truths which he taught were mingled by him with many fables and most false doctrines.   Nor did he add any signs of supernatural agency, which alone are a fitting witness to divine inspiration, since a visible work that can be from God alone, proves the teacher of truth to be invisibly inspired: but he asserted that he was sent in the power of arms, a sign that is not lacking even to robbers and tyrants.   Again, those who believed in him from the outset were not wise men practiced in things divine and human, but beastlike men who dwelt in the wilds, utterly ignorant of all divine teaching;  and it was by a multitude of such men and the force of arms that he compelled others to submit to his laws.

Lastly, no divine oracles of prophets in a previous age bore witness to him; rather did he corrupt almost all the teaching of the Old and New Testament Books to his followers, lest he should thereby be convicted of falsehood.  Thus it is evident that those who believe his words believe lightly

That Those Things Which Cannot Be Investigated By Reason Are Fittingly Proposed To Man As An Object Of Faith.

It may appear to some that those things which cannot be investigated by reason ought not to be proposed to man as an object of faith: because divine wisdom provides for each thing according to the mode of its nature. We must therefore prove that it is necessary also for those things which surpass reason to be proposed by God to man as an object of faith.

For no man tends to do a thing by his desire and endeavor unless it be previously known to him. Wherefore since man is directed by divine providence to a higher good than human frailty can attain in the present life, as we shall show in the sequel, it was necessary for his mind to be bidden to something higher than those things to which our reason can reach in the present life, so that he might learn to aspire, and by his endeavors to tend to something surpassing the whole state of the present life. And this is especially competent to the Christian religion, which alone promises goods spiritual and eternal: for which reason it proposes many things surpassing the thought of man: whereas the old law which contained promises of temporal things, proposed few things that are above human inquiry. It was with this motive that the philosophers, in order to wean men from sensible pleasures to virtue, took care to show that there are other goods of greater account than those which appeal to the senses, the taste of which things affords much greater delight to those who devote themselves to active or contemplative virtues.

Again it is necessary for this truth to be proposed to man as an object of faith in order that he may have truer knowledge of God. For then alone do we know God truly, when we believe that He is far above all that man can possibly think of God, because the divine essence surpasses man’s natural knowledge, as stated above. Hence by the fact that certain things about God are proposed to man, which surpasses his reason, he is strengthened in his opinion that God is far above what he is able to think.

There results also another advantage from this, namely, the checking of presumption which is the mother of error. For some there are who presume so far on their wits that they think themselves capable of measuring the whole of nature of things by their intellect, in that they esteem all things true which they see, and false which they see not. Accordingly, in order that man’s mind might be freed from this presumption, and seek the truth humbly, it was necessary that certain things far surpassing his intellect should be proposed to man by God.

Yet another advantage is made apparently y the words of the Philosopher (Ethic 10). For when a certain Simonides maintained tha man should neglect the knowledge of God, and apply his mind to human affairs, and declared that a man ought to relish human things, and a mortal, mortal things: the Philosopher contradicted him, saying that a man ought to devote himself to immortal and divine things as much as he can. Hence he says (De Anima 11) that though it is but little that we perceive of higher substances, yet that little is more loved and desired than all the knowledge we have of lower substances. He also says (De Caelo et Mundo 2) that when questions about the heavenly bodies can e answered by a short and probable solution, it happens that the hearer is very much rejoiced. All this shows that however imperfect the knowledge of the highest things may be, it bestows very great perfection on the soul: and consequently, although human reason is unable to grasp fully things that are above reason, it nevertheless acquires much perfection, if at least it holds things, in any way whatever, by faith.

Wherefore it is written Many things are shown to thee above the understanding of men (Ecclus 3:25), and The things…that are of God no man knows, but the Spirit of God: but to us God has revealed them by His Spirit (1 Cor 2:10-11).