A man’s got to know his limitations.
1 Now, it seems that some objection may be offered against what we have said, on the basis of a text of Augustine which requires careful interpretation. In fact, he says in Book IX of The Trinity: “Just as the mind gathers knowledge of bodily things through the bodily senses, so does it obtain knowledge of incorporeal things through itself. And so, it knows itself through itself, since it is incorporeal.” Indeed, it does appear from these words that our mind understands itself, through itself, and by understanding itself it understands separate substances. And this is in opposition to what was shown above. Therefore, it is necessary to investigate how our soul understands itself through itself.
2 Now, it cannot be said that it understands what it is, through itself. For, a cognitive potency becomes an actual knower by the fact that there is present in it that whereby the knowing is accomplished. Of course, if it be present in a potential way in the potency, one knows potentially; but if it be there actually, one knows actually; and if it be there in an intermediate fashion, one knows habitually. But the soul is always actually present to itself, never merely potentially or habitually. So, if the soul knows itself through itself, in the sense of what it is, it will always actually understand what it is. And this is plainly false.
3 Again, if the soul understands what it is, through itself, and if every man has a soul, then every man knows what soul is. And this is plainly false.
Notes More than plainly, and really the only counter-argument our good saint needs.
4 Moreover, the knowledge which comes about through something naturally implanted in us is natural, as is the case with indemonstrable principles which are known through the light of the agent intellect.
If, then, we know concerning the soul what it is, through the soul itself, then this will be something naturally known. Now, in the case of things that are naturally known no one can err; for instance, in the knowing of indemonstrable principles no one makes an error. So, no one would be in error concerning what the soul is, if the soul knew this through itself. And this is clearly false, for many men have held the opinion that the soul is this or that body, and some have thought it a number or a harmony. Therefore, the soul does not, through itself, know concerning itself what it is.
Notes Universals (of logical, moral, and mathematical) and revelation fall under “indemonstrable principles which are known through the light of the agent intellect.”
5 Besides, in any order, “that which exists through itself is prior to, and is the principle of, that which is through another.” So, that which is known through itself is known before all things that are known through another, and it is the principle of the knowing of them. Thus, the first propositions are prior to the conclusions.
If, then, the soul knows through itself what it is in itself, this will be something known through itself, and, consequently, a first known thing and a principle for the knowing of other things. Now, this is clearly false. For, what the soul is no science takes as something known; rather, it is a topic proposed for investigation, starting from other items of knowledge. Therefore, the soul does not know concerning itself what it is, through itself.
6 Now, it appears that even Augustine himself did not intend that it does. For he says in Book X of The Trinity that “the soul, when seeking knowledge of itself, does not endeavor to see itself as something absent, but takes care to observe itself as present; not to learn about itself as if it were ignorant, but to distinguish itself from what it knows as another thing.”
Thus, he makes us understand that the soul, through itself, does know itself as present, but not as distinct from other things. Consequently, he says that some people have erred on this point because they have not distinguished the soul from those things which are different from it. Now, because a thing is known from the point of view of what it is, that thing is also known in distinction from others; consequently, the definition which signifies what a thing is distinguishes the thing defined from all else. Therefore, Augustine did not wish to say that, through itself, the soul knows concerning itself what it is.
7 But neither did Aristotle intend this. Indeed, he says in Book III of On the Soul [4: 430a 2] that “the possible intellect understands itself as it does other things.” For it understands itself through an intelligible species, by which it is made actual in the genus of intelligible objects. Considered in itself, it is merely in potency in regard to intelligible being; nothing is known according to what it is potentially, but only as it is actually.
Hence, separate substances, whose substances are like something actually existing in the genus of intelligible objects, do understand, concerning themselves, what they are, through their own substances; while our possible intellect does so, through an intelligible species, by which it is made an actual agent which understands. Hence, also, Aristotle, in Book III of On the Soul [4: 429a 2], demonstrates from the very act of understanding what is the nature of the possible intellect, namely, that it is “unmixed and incorruptible,” as is clear from what we have said earlier.
8 And so, according to Augustine’s meaning, our mind knows itself through itself, in so far as it knows concerning itself, that it is. Indeed, from the fact that it perceives that it acts it perceives that it is. Of course, it acts through itself, and so, through itself, it knows concerning itself that it is.
Notes Who knew Aristotle beat Descartes to the punch by a few score centuries?
9 So, also, in regard to separate substances, the soul by knowing itself knows that they are, but not what they are, for to do the latter is to understand their substances. Indeed, when we know this about separate substances, either through demonstration or through faith, that there are certain intellectual substances, we would not be able to get this knowledge on either basis unless our soul knew on its own part this point: what it is to be intellectual. Consequently, the knowledge concerning the soul/s understanding must be used as a starting point for all that we learn about separate substances.
10 Nor is it a necessary conclusion that, if we succeed in knowing what the soul is through the speculative sciences, we must then be able to reach a knowledge of what separate substances are, through these same sciences. As a matter of fact, our act of understanding, whereby we attain to the knowledge of what our soul is, is very remote from the intelligence of a separate substance. Nevertheless, it is possible through knowing what our soul is to reach a knowledge of a remote genus for separate substances, but this does not mean an understanding of these substances.
11 Just as we know, through itself, that the soul is, in so far as we perceive its act, and we seek to discover what it is, from a knowledge of its acts and objects, by means of the principles of the speculative sciences, so also do we know concerning the things that are within our soul, such as powers and habits, that they indeed are, by virtue of our perception of their acts; but we discover what they are, from the qualitative character of their acts.