Objection 1. It would seem that the human intellect cannot attain to the vision of God in His essence. For it is written (John 1:18): "No man hath seen God at any time"; and Chrysostom in his commentary says (Hom. xiv in Joan.) that "not even the heavenly essences, namely the Cherubim and Seraphim, have ever been able to see Him as He is." Now, only equality with the angels is promised to men (Matthew 22:30): "They... shall be as the angels of God in heaven." Therefore neither will the saints in heaven see God in His essence.
Objection 2. Further, Dionysius argues thus (Div. Nom. i): "Knowledge is only of existing things." Now whatever exists is finite, since it is confined to a certain genus: and therefore God, since He is infinite, is above all existing things. Therefore there is no knowledge of Him, and He is above all knowledge.
Objection 3. Further, Dionysius (De Myst. Theol. i) shows that the most perfect way in which our intellect can be united to God is when it is united to Him as to something unknown. Now that which is seen in its essence is not unknown. Therefore it is impossible for our intellect to see God in His essence.
Objection 4. Further, Dionysius says (Ep. ad Caium Monach.) that "the darkness"--for thus he calls the abundance of light--"which screens God is impervious to all illuminations, and hidden from all knowledge: and if anyone in seeing God understood what he saw, he saw not God Himself, but one of those things that are His." Therefore no created intellect will be able to see God in His essence.
Objection 5. Further, according to Dionysius (Ep. ad Hieroth.) "God is invisible on account of His surpassing glory." Now His glory surpasses the human intellect in heaven even as on the way. Therefore since He is invisible on the way, so will He be in heaven.
Objection 6. Further, since the intelligible object is the perfection of the intellect, there must needs be proportion between intelligible and intellect, as between the visible object and the sight. But there is no possible proportion between our intellect and the Divine essence, since an infinite distance separates them. Therefore our intellect will be unable to attain to the vision of the Divine essence.
Objection 7. Further, God is more distant from our intellect than the created intelligible is from our senses. But the senses can nowise attain to the sight of a spiritual creature. Therefore neither will our intellect be able to attain to the vision of the Divine essence.
Objection 8. Further, whenever the intellect understands something actually it needs to be informed with the likeness of the object understood, which likeness is the principle of the intellectual operation terminating in that object, even as heat is the principle of heating. Accordingly if our intellect understands God, this must be by means of some likeness informing the intellect itself. Now this cannot be the very essence of God, since form and thing informed must needs have one being, while the Divine essence differs from our intellect in essence and being. Therefore the form whereby our intellect is informed in understanding God must needs be a likeness impressed by God on our intellect. But this likeness, being something created, cannot lead to the knowledge of God except as an effect leads to the knowledge of its cause. Therefore it is impossible for our intellect to see God except through His effect. But to see God through His effect is not to see Him in His essence. Therefore our intellect will be unable to see God in His essence.
Objection 9. Further, the Divine essence is more distant from our intellect than any angel or intelligence. Now according to Avicenna (Metaph. iii), "the existence of an intelligence in our intellect does not imply that its essence is in our intellect," because in that case our knowledge of the intelligence would be a substance and not an accident, "but that its likeness is impressed on our intellect." Therefore neither is God in our intellect, to be understood by us, except in so far as an impression of Him is in our intellect. But this impression cannot lead to the knowledge of the Divine essence, for since it is infinitely distant from the Divine essence, it degenerates to another image much more than if the image of a white thing were to degenerate to the image of a black thing. Therefore, just as a person in whose sight the image of a white thing degenerates to the image of a black thing, on account of an indisposition in the organ, is not said to see a white thing, so neither will our intellect be able to see God in His essence, since it understands God only by means of this impression.
Objection 10. Further, "In things devoid of matter that which understands is the same as that which is understood" (De Anima iii). Now God is supremely devoid of matter. Since then our intellect, which is created, cannot attain to be an uncreated essence, it is impossible for our intellect to see God in His essence.
Objection 11. Further, whatever is seen in its essence is known as to what it is. But our intellect cannot know of God what He is, but only what He is not as Dionysius (Coel. Hier. ii) and Damascene (De Fide Orth. i) declare. Therefore our intellect will be unable to see God in His essence.
Objection 12. Further, every infinite thing, as such, is unknown. But God is in every way infinite. Therefore He is altogether unknown. Therefore it will be impossible for Him to be seen in His essence by a created intellect.
Objection 13. Further, Augustine says (De Videndo Deo: Ep. cxlvii): "God is by nature invisible." Now that which is in God by nature cannot be otherwise. Therefore it is impossible for Him to be seen in His essence.
Objection 14. Further, whatever is in one way and is seen in another way is not seen as it is. Now God is in one way and will be seen in another way by the saints in heaven: for He according to His own mode, but will be seen by the saints according to their mode. Therefore He will not be seen by the saints as He is, and thus will not be seen in His essence.
Objection 15. Further, that which is seen through a medium is not seen in its essence. Now God will be seen in heaven through a medium which is the light of glory, according to Psalm 35:10, "In Thy light we shall see light." Therefore He will not be seen in His essence.
Objection 16. Further, in heaven God will be seen face to face, according to 1 Corinthians 13:12. Now when we see a man face to face, we see him through his likeness. Therefore in heaven God will be seen through His likeness, and consequently not in His essence.
On the contrary, It is written (1 Corinthians 13:12): "We see now through a glass in a dark manner, but then face to face." Now that which is seen face to face is seen in its essence. Therefore God will be seen in His essence by the saints in heaven.
Further, it is written (1 John 3:2): "When He shall appear we shall be like to Him, because we shall see Him as He is." Therefore we shall see Him in His essence.
Further, a gloss on 1 Corinthians 15:24, "When He shall have delivered up the kingdom to God and the Father," says: "Where," i.e. in heaven, "the essence of Father, Son, and Holy Ghost shall be seen: this is given to the clean of heart alone and is the highest bliss." Therefore the blessed will see God in His essence.
Further, it is written (John 14:21): "He that loveth Me shall be loved of My Father; and I will love him, and will manifest Myself to him." Now that which is manifested is seen in its essence. Therefore God will be seen in His essence by the saints in heaven.
Further, Gregory commenting (Moral. xviii) on the words of Exodus 33:20, "Man shall not see Me and live," disapproves of the opinion of those who said that "in this abode of bliss God can be seen in His glory but not in His nature; for His glory differs not from His nature." But His nature is His essence. Therefore He will be seen in His essence.
Further, the desire of the saints cannot be altogether frustrated. Now the common desire of the saints is to see God in His essence, according to Exodus 33:13, "Show me Thy glory"; Psalm 79:20, "Show Thy face and we shall be saved"; and John 14:8, "Show us the Father and it is enough for us." Therefore the saints will see God in His essence.
I answer that, Even as we hold by faith that the last end of man's life is to see God, so the philosophers maintained that man's ultimate happiness is to understand immaterial substances according to their being. Hence in reference to this question we find that philosophers and theologians encounter the same difficulty and the same difference of opinion. For some philosophers held that our passive intellect can never come to understand separate substances. thus Alfarabius expresses himself at the end of his Ethics, although he says the contrary in his book On the Intelligence, as the Commentator attests (De Anima iii). In like manner certain theologians held that the human intellect can never attain to the vision of God in His essence. on either side they were moved by the distance which separates our intellect from the Divine essence and from separate substances. For since the intellect in act is somewhat one with the intelligible object in act, it would seem difficult to understand how the created intellect is made to be an uncreated essence. Wherefore Chrysostom says (Hom. xiv in Joan.): "How can the creature see the uncreated?" Those who hold the passive intellect to be the subject of generation and corruption, as being a power dependent on the body, encounter a still greater difficulty not only as regards the vision of God but also as regards the vision of any separate substances. But this opinion is altogether untenable. First, because it is in contradiction to the authority of canonical scripture, as Augustine declares (De Videndo Deo: Ep. cxlvii). Secondly, because, since understanding is an operation most proper to man, it follows that his happiness must be held to consist in that operation when perfected in him. Now since the perfection of an intelligent being as such is the intelligible object, if in the most perfect operation of his intellect man does not attain to the vision of the Divine essence, but to something else, we shall be forced to conclude that something other than God is the object of man's happiness: and since the ultimate perfection of a thing consists in its being united to its principle, it follows that something other than God is the effective principle of man, which is absurd, according to us, and also according to the philosophers who maintain that our souls emanate from the separate substances, so that finally we may be able to understand these substances. Consequently, according to us, it must be asserted that our intellect will at length attain to the vision of the Divine essence, and according to the philosophers, that it will attain to the vision of separate substances.
It remains, then, to examine how this may come about. For some, like Alfarabius and Avempace, held that from the very fact that our intellect understands any intelligible objects whatever, it attains to the vision of a separate substance. To prove this they employ two arguments. The first is that just as the specific nature is not diversified in various individuals, except as united to various individuating principles, so the idea understood is not diversified in me and you, except in so far as it is united to various imaginary forms: and consequently when the intellect separates the idea understood from the imaginary forms, there remains a quiddity understood, which is one and the same in the various persons understanding it, and such is the quiddity of a separate substance. Hence, when our intellect attains to the supreme abstraction of any intelligible quiddity, it thereby understands the quiddity of the separate substance that is similar to it. The second argument is that our intellect has a natural aptitude to abstract the quiddity from all intelligible objects having a quiddity. If, then, the quiddity which it abstracts from some particular individual be a quiddity without a quiddity, the intellect by understanding it understands the quiddity of the separate substance which has a like disposition, since separate substances are subsisting quiddities without quiddities; for the quiddity of a simple thing is the simple thing itself, as Avicenna says (Met. iii). On the other hand if the quiddity abstracted from this particular sensible be a quiddity that has a quiddity, it follows that the intellect has a natural aptitude to abstract this quiddity, and consequently since we cannot go on indefinitely, we shall come to some quiddity without a quiddity, and this is what we understand by a separate quiddity [Cf. I, 88, 2].
But this reasoning is seemingly inconclusive. First, because the quiddity of the material substance, which the intellect abstracts, is not of the same nature as the quiddity of the separate substances, and consequently from the fact that our intellect abstracts the quiddities of material substances and knows them, it does not follow that it knows the quiddity of a separate substance, especially of the Divine essence, which more than any other is of a different nature from any created quiddity. Secondly, because granted that it be of the same nature, nevertheless the knowledge of a composite thing would not lead to the knowledge of a separate substance, except in the point of the most remote genus, namely substance: and such a knowledge is imperfect unless it reach to the properties of a thing. For to know a man only as an animal is to know him only in a restricted sense and potentially: and much less is it to know only the nature of substance in him. Hence to know God thus, or other separate substances, is not to see the essence of God or the quiddity of a separate substance, but to know Him in His effect and in a mirror as it were. For this reason Avicenna in his Metaphysics. propounds another way of understanding separate substances, to wit that separate substances are understood by us by means of intentions of their quiddities, such intentions being images of their substances, not indeed abstracted therefrom, since they are immaterial, but impressed thereby on our souls. But this way also seems inadequate to the Divine vision which we seek. For it is agreed that "whatever is received into any thing is therein after the mode of the recipient": and consequently the likeness of the Divine essence impressed on our intellect will be according to the mode of our intellect: and the mode of our intellect falls short of a perfect reception of the Divine likeness. Now the lack of perfect likeness may occur in as many ways, as unlikeness may occur. For in one way there is a deficient likeness, when the form is participated according to the same specific nature, but not in the same measure of perfection: such is the defective likeness in a subject that has little whiteness in comparison with one that has much. In another way the likeness is yet more defective, when it does not attain to the same specific nature but only to the same generic nature: such is the likeness of an orange-colored or yellowish object in comparison with a white one. In another way, still more defective is the likeness when it does not attain to the same generic nature, but only to a certain analogy or proportion: such is the likeness of whiteness to man, in that each is a being: and in this way every likeness received into a creature is defective in comparison with the Divine essence. Now in order that the sight know whiteness, it is necessary for it to receive the likeness of whiteness according to its specific nature, although not according to the same manner of being because the form has a manner of being in the sense other from that which it has in the thing outside the soul: for if the form of yellowness were received into the eye, the eye would not be said to see whiteness. In like manner in order that the intellect understand a quiddity, it is necessary for it to receive its likeness according to the same specific nature, although there may possibly not be the same manner of being on either side: for the form which is in the intellect or sense is not the principle of knowledge according to its manner of being on both sides, but according to its common ratio with the external object. Hence it is clear that by no likeness received in the created intellect can God be understood, so that His essence be seen immediately. And for this reason those who held the Divine essence to be seen in this way alone, said that the essence itself will not be seen, but a certain brightness, as it were a radiance thereof. Consequently neither does this way suffice for the Divine vision that we seek.
Therefore we must take the other way, which also certain philosophers held, namely Alexander and Averroes (De Anima iii.). For since in every knowledge some form is required whereby the object is known or seen, this form by which the intellect is perfected so as to see separate substances is neither a quiddity abstracted by the intellect from composite things, as the first opinion maintained, nor an impression left on our intellect by the separate substance, as the second opinion affirmed; but the separate substance itself united to our intellect as its form, so as to be both that which is understood, and that whereby it is understood. And whatever may be the case with other separate substances, we must nevertheless allow this to be our way of seeing God in His essence, because by whatever other form our intellect were informed, it could not be led thereby to the Divine essence. This, however, must not be understood as though the Divine essence were in reality the form of our intellect, or as though from its conjunction with our intellect there resulted one being simply, as in natural things from the natural form and matter: but the meaning is that the proportion of the Divine essence to our intellect is as the proportion of form to matter. For whenever two things, one of which is the perfection of the other, are received into the same recipient, the proportion of one to the other, namely of the more perfect to the less perfect, is as the proportion of form to matter: thus light and color are received into a transparent object, light being to color as form to matter. When therefore intellectual light is received into the soul, together with the indwelling Divine essence, though they are not received in the same way, the Divine essence will be to the intellect as form to matter: and that this suffices for the intellect to be able to see the Divine essence by the Divine essence itself may be shown as follows.
As from the natural form (whereby a thing has being) and matter, there results one thing simply, so from the form whereby the intellect understands, and the intellect itself, there results one thing intelligibly. Now in natural things a self-subsistent thing cannot be the form of any matter, if that thing has matter as one of its parts, since it is impossible for matter to be the form of a thing. But if this self-subsistent thing be a mere form, nothing hinders it from being the form of some matter and becoming that whereby the composite itself is [Literally,--and becoming the 'whereby-it-is' of the composite itself] as instanced in the soul. Now in the intellect we must take the intellect itself in potentiality as matter, and the intelligible species as form; so that the intellect actually understanding will be the composite as it were resulting from both. Hence if there be a self-subsistent thing, that has nothing in itself besides that which is intelligible, such a thing can by itself be the form whereby the intellect understands. Now a thing is intelligible in respect of its actuality and not of its potentiality (Met. ix): in proof of which an intelligible form needs to be abstracted from matter and from all the properties of matter. Therefore, since the Divine essence is pure act, it will be possible for it to be the form whereby the intellect understands: and this will be the beatific vision. Hence the Master says (Sent. ii, D, 1) that the union of the body with the soul is an illustration of the blissful union of the spirit with God.
Reply to Objection 1. The words quoted can be explained in three ways, according to Augustine (De Videndo Deo: Ep. cxlvii). In one way as excluding corporeal vision, whereby no one ever saw or will see God in His essence; secondly, as excluding intellectual vision of God in His essence from those who dwell in this mortal flesh; thirdly, as excluding the vision of comprehension from a created intellect. It is thus that Chrysostom understands the saying wherefore he adds: "By seeing, the evangelist means a most clear perception, and such a comprehension as the Father has of the Son." This also is the meaning of the evangelist, since he adds: "The Only-begotten Son Who is in the bosom of the Father, He hath declared Him": his intention being to prove the Son to be God from His comprehending God.
Reply to Objection 2. Just as God, by His infinite essence, surpasses all existing things which have a determinate being, so His knowledge, whereby He knows, is above all knowledge. Wherefore as our knowledge is to our created essence, so is the Divine knowledge to His infinite essence. Now two things contribute to knowledge, to wit, the knower and the thing known. Again, the vision whereby we shall see God in His essence is the same whereby God sees Himself, as regards that whereby He is seen, because as He sees Himself in His essence so shall we also see Him. But as regards the knower there is the difference that is between the Divine intellect and ours. Now in the order of knowledge the object known follows the form by which we know, since by the form of a stone we see a stone: whereas the efficacy of knowledge follows the power of the knower: thus he who has stronger sight sees more clearly. Consequently in that vision we shall see the same thing that God sees, namely His essence, but not so effectively.
Reply to Objection 3. Dionysius is speaking there of the knowledge whereby wayfarers know God by a created form, whereby our intellect is informed so as to see God. But as Augustine says (De Videndo Deo: Ep. cxlvii), "God evades every form of our intellect," because whatever form our intellect conceive, that form is out of proportion to the Divine essence. Hence He cannot be fathomed by our intellect: but our most perfect knowledge of Him as wayfarers is to know that He is above all that our intellect can conceive, and thus we are united to Him as to something unknown. In heaven, however, we shall see Him by a form which is His essence, and we shall be united to Him as to something known.
Reply to Objection 4. God is light (John 1:9). Now illumination is the impression of light on an illuminated object. And since the Divine essence is of a different mode from any likeness thereof impressed on the intellect, he (Dionysius) says that the "Divine darkness is impervious to all illumination," because, to wit, the Divine essence, which he calls "darkness" on account of its surpassing brightness, remains undemonstrated by the impression on our intellect, and consequently is "hidden from all knowledge." Therefore if anyone in seeing God conceives something in his mind, this is not God but one of God's effects.
Reply to Objection 5. Although the glory of God surpasses any form by which our intellect is informed now, it does not surpass the Divine essence, which will be the form of our intellect in heaven: and therefore although it is invisible now, it will be visible then.
Reply to Objection 6. Although there can be no proportion between finite and infinite, since the excess of the infinite over the finite is indeterminate, there can be proportionateness or a likeness to proportion between them: for as a finite thing is equal to some finite thing, so is an infinite thing equal to an infinite thing. Now in order that a thing be known totally, it is sometimes necessary that there be proportion between knower and known, because the power of the knower needs to be adequate to the knowableness of the thing known, and equality is a kind of proportion. Sometimes, however, the knowableness of the thing surpasses the power of the knower, as when we know God, or conversely when He knows creatures: and then there is no need for proportion between knower and known, but only for proportionateness; so that, to wit, as the knower is to the knowable object, so is the knowable object to the fact of its being known: and this proportionateness suffices for the infinite to be known by the finite, or conversely.
We may also reply that proportion according to the strict sense in which it is employed signifies a ratio of quantity to quantity based on a certain fixed excess or equality; but is further transferred to denote any ratio of any one thing to another; and in this sense we say that matter should be proportionate to its form. In this sense nothing hinders our intellect, although finite, being described as proportionate to the vision of the Divine essence; but not to the comprehension thereof, on account of its immensity.
Reply to Objection 7. Likeness and distance are twofold. One is according to agreement in nature; and thus God is more distant from the created intellect than the created intelligible is from the sense. The other is according to proportionateness; and thus it is the other way about, for sense is not proportionate to the knowledge of the immaterial, as the intellect is proportionate to the knowledge of any immaterial object whatsoever. It is this likeness and not the former that is requisite for knowledge, for it is clear that the intellect understanding a stone is not like it in its natural being; thus also the sight apprehends red honey and red gall, though it does not apprehend sweet honey, for the redness of gall is more becoming to honey as visible, than the sweetness of honey to honey.
Reply to Objection 8. In the vision wherein God will be seen in His essence, the Divine essence itself will be the form, as it were, of the intellect, by which it will understand: nor is it necessary for them to become one in being, but only to become one as regards the act of understanding.
Reply to Objection 9. We do not uphold the saying of Avicenna as regards the point at issue, for in this other philosophers also disagree with him. Unless perhaps we might say that Avicenna refers to the knowledge of separate substances, in so far as they are known by the habits of speculative sciences and the likeness of other things. Hence he makes this statement in order to prove that in us knowledge is not a substance but an accident. Nevertheless, although the Divine essence is more distant, as to the property of its nature, from our intellect, than is the substance of an angel, it surpasses it in the point of intelligibility, since it is pure act without any admixture of potentiality, which is not the case with other separate substances. Nor will that knowledge whereby we shall see God in His essence be in the genus of accident as regards that whereby He will be seen, but only as regards the act of the one who understands Him, for this act will not be the very substance either of the person understanding or of the thing understood.
Reply to Objection 10. A substance that is separate from matter understands both itself and other things; and in both cases the authority quoted can be verified. For since the very essence of a separate substance is of itself intelligible and actual, through being separate from matter, it is clear that when a separate substance understands itself, that which understands and that which is understood are absolutely identical, for it does not understand itself by an intention abstracted from itself, as we understand material objects. And this is apparently the meaning of the Philosopher (De Anima iii.) as indicated by the Commentator (De Anima iii). But when it understands other things, the object actually understood becomes one with the intellect in act, in so far as the form of the object understood becomes the form of the intellect, for as much as the intellect is in act; not that it becomes identified with the essence of the intellect, as Avicenna proves (De Natural. vi.), because the essence of the intellect remains one under two forms whereby it understands two things in succession, in the same way as primary matter remains one under various forms. Hence also the Commentator (De Anima iii.) compares the passive intellect, in this respect, to primary matter. Thus it by no means follows that our intellect in seeing God becomes the very essence of God, but that the latter is compared to it as its perfection or form.
Reply to Objection 11. These and all like authorities must be understood to refer to the knowledge whereby we know God on the way, for the reason given above.
Reply to Objection 12. The infinite is unknown if we take it in the privative sense, as such, because it indicates removal of completion whence knowledge of a thing is derived. Wherefore the infinite amounts to the same as matter subject to privation, as stated in Phys. iii. But if we take the infinite in the negative sense, it indicates the absence of limiting matter, since even a form is somewhat limited by its matter. Hence the infinite in this sense is of itself most knowable; and it is in this way that God is infinite.
Reply to Objection 13. Augustine is speaking of bodily vision, by which God will never be seen. This is evident from what precedes: "For no man hath seen God at any time, nor can any man see Him as these things which we call visible are seen: in this way He is by nature invisible even as He is incorruptible." As, however, He is by nature supremely being, so He is in Himself supremely intelligible. But that He be for a time not understood by us is owing to our defect: wherefore that He be seen by us after being unseen is owing to a change not in Him but in us.
Reply to Objection 14. In heaven God will be seen by the saints as He is, if this be referred to the mode of the object seen, for the saints will see that God has the mode which He has. But if we refer the mode to the knower, He will not be seen as He is, because the created intellect will not have so great an efficacy in seeing, as the Divine essence has to the effect of being seen.
Reply to Objection 15. There is a threefold medium both in bodily and in intellectual vision. The first is the medium "under which" the object is seen, and this is something perfecting the sight so as to see in general, without determining the sight to any particular object. Such is bodily light in relation to bodily vision; and the light of the active intellect in relation to the passive intellect, in so far as this light is a medium. The second is the light "by which" the object is seen, and this is the visible form whereby either sight is determined to a special object, for instance by the form of a stone to know a stone. The third is the medium "in which" it is seen; and this is something by gazing on which the sight is led to something else: thus by looking in a mirror it is led to see the things reflected in the mirror, and by looking at an image it is led to the thing represented by the image. In this way, too, the intellect from knowing an effect is led to the cause, or conversely. Accordingly in the heavenly vision there will be no third medium, so that, to wit, God be known by the images of other things, as He is known now, for which reason we are said to see now in a glass: nor will there be the second medium, because the essence itself of God will be that whereby our intellect will see God. But there will only be the first medium, which will upraise our intellect so that it will be possible for it to be united to the uncreated substance in the aforesaid manner. Yet this medium will not cause that knowledge to be mediate, because it does not come in between the knower and the thing known, but is that which gives the knower the power to know [Cf. I, 12, 5].
Reply to Objection 16. Corporeal creatures are not said to be seen immediately, except when that which in them is capable of being brought into conjunction with the sight is in conjunction therewith. Now they are not capable of being in conjunction with the sight of their essence on account of their materiality: hence they are seen immediately when their image is in conjunction with the sight. But God is able to be united to the intellect by His essence: wherefore He would not be seen immediately, unless His essence were united to the intellect: and this vision, which is effected immediately, is called "vision of face". Moreover the likeness of the corporeal object is received into the sight according to the same ratio as it is in the object, although not according to the same mode of being. Wherefore this likeness leads to the object directly: whereas no likeness can lead our intellect in this way to God, as shown above: and for this reason the comparison fails.
Source: Summa Theologica (New Advent)