We’re still on the theme that you need God to see God. Indeed, you need God to know anything.
1 For such a noble vision, the created intellect must be elevated by means of an influx of divine goodness.
2 Indeed, it is not possible for what is the proper form of one thing to become the form of another unless the latter thing participates some likeness of the thing to which the form belongs. For instance, light can only become the act of a body if the body participates somewhat in the diaphanous. But the divine essence is the proper intelligible form for the divine intellect and is proportioned to it; in fact, these three are one in God: the intellect, that whereby understanding is accomplished, and the object which is understood. So, it is impossible for this essence to become the intelligible form of a created intellect unless by virtue of the fact that the created intellect participates in the divine likeness. Therefore, this participation in the divine likeness is necessary so that the substance of God may be seen.
3 Again, nothing is receptive of a more sublime form unless it be elevated by means of a disposition to the capacity for this form, for a proper act is produced in a proper potency. Now, the divine essence is a higher form than any created intellect. So, in order that the divine essence may become the intelligible species for a created intellect, which is needed in order that the divine substance may be seen, it is necessary for the created intellect to be elevated for this purpose by a more sublime disposition.
Notes Another way to put this is that you need God to know any truth.
4 Besides, suppose that two things are not united at first, and then later they are united; this must be done by changing both of them, or at least one. Now, suppose that a created intellect starts for the first time to see God’s substance; then, necessarily, according to the preceding arguments, the divine essence must be united with it for the first time as an intelligible species. Of course, it is not possible for the divine essence to be changed, as we showed above. So, this union must start to exist by means of a change in the created intellect. In fact, this change can only come about by means of the created intellect acquiring some new disposition.
Indeed, the same conclusion follows if it be granted that a created intellect is endowed with such a vision from the start of its creation. For, if this vision exceeds the capacity of a created nature, as we have proved, then any created intellect may be understood to enjoy complete existence in the species proper to its nature, without seeing the substance of God. Hence, whether it begins to see God at the start of its existence, or later, something must be added to its nature.
5 Furthermore, nothing can be elevated to a higher operation unless because its power is strengthened. But there are two possible ways in which a thing’s power may be strengthened. One way is by a simple intensification of the power itself; thus, the active power of a hot thing is increased by an intensification of the heat, so that it is able to perform a stronger action of the same species.
A second way is by the imposition of a new form; thus, the power of a diaphanous object is increased so that it can shine with light, by virtue of its becoming actually luminous, through the form of light received for the first time within it. And in fact, this latter kind of increase of power is needed for the acquisition of an operation of another species.
Now, the power of a created intellect is not sufficient to see the divine substance, as is clear from what we have said. So, its power must be increased in order that it may attain such a vision. But the increase through the intensification of a natural power does not suffice, since this vision is not of the same essential type as the vision proper to a natural created intellect. This is evident from the difference between the objects of these visions. Therefore, an increase of the intellectual power by means of the acquisition of a new disposition must be accomplished.
Notes Another—and the same as above—way to put this, is that you need God to know that which cannot be proved.
6 However, since we reach the knowledge of intelligible things from sensible things, we also take over the names proper to sense knowledge for intellectual knowledge, especially the ones which apply to sight, which, compared to the other senses, is more noble and more spiritual, and so more closely related to the intellect. Thus it is that this intellectual knowledge is called vision. And since corporeal vision is not accomplished without light, those things whereby intellectual vision is perfected take on the name fight.
Hence, even Aristotle, in Book III of On the Soul [5: 430a 15], likens the agent intellect to light, because of the fact that the agent intellect makes things actually intelligible, just as light in a way makes things actually visible. Therefore, this disposition whereby the created intellect is raised to the intellectual vision of divine substance is fittingly called the light of glory; not because it makes some object actually intelligible, as does the light of the agent intellect, but because it makes the intellect actually powerful enough to understand.
7 Now, this is the light of which it is said in the Psalms (35:10): “In Thy light we shall see the light,” that is, of the divine substance. And it is said in the Apocalypse (22:5; see also 21:23): “The city,” that is, of the Blessed, “has no need of the sun, nor of the moon . . . for the glory of God bath enlightened it.”
And it is said in Isaiah (60:19): “You shall no more have the sun for your light by day, neither shall the brightness of the moon enlighten you; but the Lord shall be an everlasting light for you, and your God for your glory.”
It is also so, because in God to be and to understand is the same thing; and because He is for all the cause of understanding, He is said to be the light (John 1:9): “That was the true light which enlightened every man that comes into this world” (John 1:9); and: “God is light” (1 John 1:5); and in the Psalms (103:7): “You…are clothed with light as with a garment.” And for this reason also, both God and the angels are described in Sacred Scripture in figures of fire (Exod. 24:17; Acts 2:3; Ps 103:4), because of the brilliance of fire.