One of the more striking aspects of human knowing is the ability of the mind to bend back upon itself entirely. This ability renders us self-conscious. In other words, I am only really present to myself when knowing something other than myself. When we know anything, we know that we know (furthermore, we know that we know that we know, and so on). It is this power that renders us able to know our limits; for we cannot come to know our limits unless we have the ability to transcend them, so to speak. In other words, it is possible for a dummy to know that he is dumb. Moreover, a dummy can come to accept the fact that he is dumb, which is why dummies can become great saints.
This same ability towards self-transcendence allows us to become aware of the profound limitations of human intelligence in general. For in the end, we are, all of us, dummies -- even the brightest of us. Human knowing is limited on all sides, that is, from above, from below, from the front and from behind. We are limited both vertically and horizontally. Now there must be a lesson for us in all of this, but before we focus on just what this lesson might be, let us examine each of these limits in particular.
Some of us might have already heard of Heisenberg's uncertainty principle. Werner Heisenberg was a German born physicist who discovered that it is not possible to know the position and velocity of an electron at the same time. Our knowledge of the one (i.e., position) is gained at the expense of our knowledge of the other (velocity). The information about the probability of locating the electron somewhere in the space of a hydrogen atom is in the form of a probability distribution. An electron in the atom is described by a wave function.
This principle has been terribly abused over the years by physicists trying to philosophize on the implications of it, not to mention theologians. Some have gone so far as to suggest that Heisenberg's principle implies that everything in the universe is indeterminate, or that all of our knowledge is ultimately uncertain. These abuses for the most part are reducible to the logical fallacy of part and whole, which involves attributing to the whole what belongs only to a part. For not everything can be uncertain, for even Heisenberg was certain of the uncertainty principle and of the premises that lead up to it. Nevertheless, the principle does underscore the inherent limits of our knowledge of matter at the sub-atomic level. There is mystery buried within the sub-atomic regions of the physical universe.
The philosophy of nature also highlights the inherent limits of our knowledge of material things. A thing is knowable in so far as it is in act. But a material thing is a unity of potentiality (ultimate matter) and actuality (form). Our knowledge of the "essences" of material things is opaque by virtue of matter's opacity; for matter is potentiality, and a thing is not knowable in so far as it is in potentiality, but in so far as it is in act. An essence having intentional existence is still clouded by potentiality because essence includes matter and form -- a carrot, for example, is essentially a material thing.
That is why our definitions of material things are imperfect. A perfect definition includes a genus and a specific difference, but it is not always possible to know the specific difference that renders one thing specifically different from another thing belonging to the same genus.
Our knowledge of what is above us is also limited, that is, our knowledge of God and the preternatural realm. We do not know God as He is in Himself, and what we are able to know about Him through human reason is gathered primarily through our knowledge of what He is not. It is only by means of this negative theology that we can indirectly pronounce on what He is.
We have a positive and direct knowledge of material contingent beings -- by no means exhaustive -- , and we know that a contingent being is a composite of essence and existence. To account for the received act of existing of contingent beings requires the positing of a non-contingent being. God is not a being whose essence is distinct from His act of existing. Hence, there is no composition of potency and act in God. From this point we can conclude that God is His own act of existing and that all the perfections that exist in God are identical to His act of existing. It follows that God does not have beauty, or a just will, nor does He have knowledge. Rather, He is Beauty, He is Justice, and He is His knowledge.
None of this constitutes a direct knowledge of God, but is first and foremost a knowledge of what God is not.
The knowledge that comes to us through the supernatural virtue of faith is superior to this natural theology, but faith is also a dark habit. As St. Paul says: "At present we see indistinctly, as in a mirror, but then face to face. At present I know partially; then I shall know fully, as I am fully known" (1 Cor 13, 12). Elsewhere he writes: "for we walk by faith, not by sight" (2 Cor 5, 7).
Our knowledge of angels is also indirect and dependent upon a negative method. We know through revelation that angels exist. But what they are in themselves, we do not know. Nevertheless, we can deduce a great deal about angels by focusing on what an angel is not. For example, since an angel is not a unity of spirit and matter, it follows that there is no "genus" of angel, as animal is the genus in the definition of man. It follows that every angel is its own species. It also follows that angels are not subject to place and time, and that their natural mode of knowing is not via abstraction. Hence, their knowing is not discursive and laborious, dependent upon a sensible species. The mind of an angel, on the contrary, is specified from the instant of its creation. We can deduce that the angelic mode of knowing has a far greater likeness to the divine than does that of man. Perhaps the difference between the angelic intellect and the human intellect can be compared somewhat to the difference between the knowing ability of a dog and that of man (man is to angel as dog is to man).
But we don't know the angelic realm in itself. The angelic liturgy in which myriads of angels unceasingly exclaim "Holy, holy, holy is the Lord God almighty, who was, and who is, and who is to come" (Rv 4, 8) is closed to us. A thick ceiling of fog covers our heads, so to speak.
Our knowledge is also profoundly limited from the front. For we don't know what the future holds for us. For the most part, we don't even know what the next day has in store for us. Consider for a moment a year of your own life and all that had occurred within that year. Imagine receiving a premonition revealing all that you were to go through for that year alone. All I know is that were I to receive a premonition revealing all that I was to go through this year alone, I'd have had a nervous breakdown. The weight of the information would have been far too overwhelming. That is why we need not anxiously focus on the possibilities before us, but take one day at a time: "Do not worry about tomorrow; tomorrow will take care of itself. Sufficient for a day is its own evil" (Mt 6, 34).
Our knowledge is also limited from behind. This is especially evident after 40. We just don't seem to remember things we at one time were able to remember, such as names, faces, and events.
There is a lesson for teachers in regards to the rather frustrating phenomenon of forgetting former students. Teaching is a kind of parenthood, a spiritual begetting, so to speak. The teacher -- even the female teacher -- is a kind of father, exercising a spiritual paternity. But human paternity is a very imperfect sharing in the pre-eminent fatherhood of God; for God is the ultimate origin of all generation and being, in the order of nature as well as grace. Despite the impact we might have had on many of our former students, without the aid of divine grace, our teaching lives are fruitless.
Now parents don't forget their children. But teachers forget a great many of their students. This is a reminder that our "paternity" is only partial, and that God, who does not forget any of our students, is more perfectly and pre-eminently their father than we can ever claim to be.
Human knowing is slow, discursive, and laborious. It is intimately linked to sensation. For the natural mode of human intellection is abstraction. The active mind depends upon a phantasm produced by the synthetic sense, from which it abstracts the intelligible content of the object, impressing it upon the passive mind. To reason, which is distinct from abstraction, is to draw conclusions from given premises. We speak of children reaching the age of reason, which amounts to more than a few years afterchildbirth. But to master human reason takes years of hard work, and most people will never achieve such mastery--those who have, however, still make mistakes and are usually more aware of their limits than those who have not.
Even a glance back at the history of science or mathematics is enough to draw attention to the sluggishness of human intelligence. Adolescents routinely learn things in math class, all within the span of a semester, that have taken the most brilliant human minds (i.e., Descartes, Pascal, Newton, etc.) centuries to discover.
It is obvious that our glory lies not in our intelligence. Rather, intelligence is the glory of the Cherubim. Pseudo-Dionysius writes: "The name cherubim signifies the power to know and to see God, to receive the greatest gifts of his light, to contemplate the divine splendour in primordial power, to be filled with the gifts that bring wisdom and to share these generously with subordinates as a part of the beneficent outpouring of wisdom" (Celestial Hierarchy 7, 1).
On the contrary, human beings stand, as it were, surrounded on all sides by a thick fog that allows us to see only a few feet in front of us, a few feet behind, very little below and not much that is above us. Thus, our glory lies in humility. It lies in recognizing and accepting whole-heartedly this fourfold limitation. We have only to call out in the darkness, like a child lost in the fog; for we are weak, frail, dull of mind, forgetful, imprudent, inclined to sin, and we are the lowest creatures on the scale of the hierarchy of intellectual creatures. And despite these limitations, it even occurs to man to doubt God's existence when he has made a little progress in the world of science. Our pride is delusional. But our glory lies in humility, a humility that angels could even possibly envy.