“But this is a solecism. For since man’s final beatitude consists in his highest action, which is the action of the intelligence, if the created intelligence is never to be able to see the essential nature of God, either it will never obtain beatitude, or its beatitude will consist in something besides God: which is repugnant to the faith. For the ultimate perfection of a rational creature lies in that which is the source or principle (principium) of its being. Likewise the argument is against reason. For there is in man a natural desire to know the cause, when he observes the effect; and from this, wonder rises in men. If then the intelligence of the rational creature is incapable of attaining to the first cause of things, an inane desire must be ascribed to nature.
“Wherefore it is simply to be conceded that the blessed may see the essential nature of God.”
So this general conclusion, or assumption, is based on faith, and also leaps, as from the head of Jove, the creature of unconquerable human need, which never will admit the inaneness of its yearnings. And now, assuming the possibility of seeing God in his true nature, Thomas proves that He cannot be seen thus through the similitude of any created thing: in order to behold God’s essence some divine likeness must be imparted from the seeing power (ex parte visivae potentiae), to wit, the light of divine glory (which is consummated grace) strengthening the intelligence that it may see God. And he next shows that it is impossible to see God by the sense of sight, or any other sense or power of man’s sensible nature. For God is incorporeal. Therefore He cannot be seen through the imagination, but only through the intelligence. Nor can any created intelligence through its natural faculties see the divine essence. “Cognition takes place in so far as the known is in the knower. But the known is in the knower according to the mode and capacity (modus) of the knower. Whence any knower’s knowledge is according to the measure of his nature. If then the being of the thing to be known exceeds the measure of the knowing nature, knowledge of it will be beyond the nature of that knower.” In order to see God in His essential nature, the created intellect needs light created by God: In lumine tuo videbimus lumen. And it may be given to one created intellect to see more perfectly than another.
Do those who see God per essentiam, comprehend Him? No.
“To comprehend God is impossible for any created intelligence. To have any true thought of God is a great beatitude.... Since the created light of glory received by any created intelligence, cannot be infinite, it is impossible that any created intelligence should know God infinitely, and comprehend Him.”
Again he reasons; They who shall see God in His essence will see what they see through the divine essence united to their intelligence; they will see whatever they see at once, and not successively; for the contents of this intellectual, God-granted vision are not apprehended by means of the respective species or general images, but in and through the one divine essence. But in this life, man may not see God in His essential nature:
“The mode of cognition conforms to the nature of the knower. But our soul, so long as we live in this life, has its existence (esse) in corporeal matter. Wherefore, by nature, it knows only things that have material form, or may through such be known. Evidently the divine essence cannot be known through the natures of material things. Any cognition of God through any created likeness whatsoever, is not a vision of His essence.... Our natural cognition draws its origin from sense; it may extend itself so far as it can be conducted (manuduci) by things of sense (sensibilia). But from them our intelligence may not attain to seeing the divine essence.... Yet since sensible creatures are effects, dependant on a cause, we know from them that God exists, and that as first cause He exceeds all that He has caused. From which we may learn the difference between Himself and His creatures, to wit, that He is not any of those things which He has caused....
“Through grace a more perfect knowledge of God is had than through natural reason. For cognition through natural reason needs both images (phantasmata) received from things of sense, and the natural light of intelligence, through whose virtue we abstract intelligible conceptions from them. In both respects human cognition is aided through the revelation of grace. For the natural light of the intellect is strengthened through the infusion of light graciously given (luminis gratuiti); while the images in the man’s imagination are divinely formed so that they are expressive of things divine, rather than of what naturally is received through the senses, as appears from the visions of the prophets.”[591]
Natural reason stops with the unity of God, and can give no knowledge of the Trinity of divine Persons. Says Thomas:[592]
“It has been shown that through natural reason man can know God only from His creatures. Creatures lead to knowledge of God as effects lead to some knowledge of a cause. Only that may be known of God by natural reason which necessarily belongs to Him as the source of all existences. The creative virtue of God is common to the whole Trinity; it pertains to the unity of essence, not to the distinction of persons. Through natural reason, therefore, those things concerning God may be known which pertain to the unity of essence, but not those which pertain to the distinction of persons.... Who strives to prove the Trinity of Persons by natural reason, doubly disparages faith: first as regards the dignity of faith itself, which concerns invisible things surpassing human reason; secondly as derogating from its efficiency in drawing men to it. For when any one in order to prove the faith adduces reasons which are not cogent, he falls under the derision of the faithless; for they think that we use such arguments, and that we believe because of them. One shall not attempt to prove things of faith save by authorities, and in discussion with those who receive the authorities. With others it is enough to argue that what the faith announces is not impossible.”