Summa contra Gentiles3.46 Chapter XLVI. That in this life the soul does not understand itself by itself

A CERTAIN difficulty would seem to arise against what we have been saying, on account of a passage of Augustine which must be carefully discussed. For he says (9 De Trin. iii.): Just as the mind gathers knowledge of corporeal things by means of the senses, so does it acquire knowledge of incorporeal things by itself. Therefore it also knows itself by itself, since itself 1s incorporeal. For it would seem to follow from these words that the soul understands itself by itself, and that by understanding itself, understands separate substances: and this is contrary to what we have proved. We must, accordingly, inquire how the soul understands itself by itself.

Now it cannot possibly be said that by itself it understands what itself is. Because a cognitive power is made actually cognoscent by something in it whereby it knows. And if this be in it potentially, it knows potentially; if it be in it actually, it knows actually; and if it be in a middle way, it knows habitually. Now the soul is always actually present to itself, and never only potentially or habitually. ‘Wherefore, if the soul knows itself by itself, it will always understand actually what itself is: and this is clearly false.

Again. If the soul, by itself, understands what itself is; and since every man has a soul; every man will know what his soul is: which is evidently untrue.

Moreover. Knowledge that results from something implanted in us by nature, is itself natural: for instance the—self-evident principles which are known through the light of the active intellect. Accordingly, if by the soul itself we know what the soul is, we shall know it naturally. But no one can err in things that we know naturally: for no one errs in self-evident principles: so that no one would err about what the soul is, if the soul knew this by itself. But this is clearly false: since many have maintained the soul to be this or that body; some, that it consisted in number or harmony.! Therefore the soul does not, by itself, know what itself is.

Besides. In every order that which is per se precedes and causes that which is accidental. Accordingly that which is known per se, is known before all things that are known through something else, and is the principle through which they are known, for instance first principles in comparison with conclusions. Therefore if the soul, by itself, knows what itself is, this will be known per se, and consequently—it will be known first, and will be the principle whereby other things are known. But this is clearly false: for science does not postulate what the soul is as being something already known, but proposes it as a point of inquiry from other sources. Therefore the soul does not by itself know what itself is.

But it is clear that neither did Augustine intend this. For he says (10 De Trin. ix.) that when the soul seeks self-knowledge, it does not seek to see itself as though it were absent, but to discern itself as present: not to know itself, as though it knew not; but in order to distinguish itself from what wt knows to be distinct. Whereby he gives one to understand that by itself the soul knows itself as present to itself, but not as distinct from other things. Hence he says that some erred in not distinguishing the soul from things that are different from it. Now through knowing what a thing is, one knows it as distinct from others: wherefore a definition which states what a thing is, distinguishes the thing defined from all others. Consequently Augustine did not mean that the soul by itself knows what itself is.

Neither did Aristotle mean this. He says in fact (3 De Anima, iv.) that the possible intellect understands itself even as it understands other things. Because it understands itself by means of an intelligible species, by which it is brought to actual intelligibility. For, considered in itself, it is only potentially an intelligible being: now nothing is known according as it is in potentiality, but only according as it is in act. Wherefore separate substances, the substance whereof is as something actual in the genus of things intelligible, understand by their very substance what they are: whereas our possible intellect understands what it is, through the intelligible species by which it is made actually understanding. And so Aristotle (3 De Anima, iv.) shows the nature of the possible intellect from the act of understanding, namely that it is unmixed with the body and incorruptible, as we explained above.!

Accordingly Augustine means to say that our mind knows itself by itself, inasmuch as it knows that it is: because by the very fact that it perceives itself to act, it perceives that it exists; and since it acts by itself, it knows by itself that it exists.

In this way then the soul, by knowing itself, knows of the separate substances that they are; but not what they are, which is to understand their substance. For when either by demonsiration or by faith we know about separate substances that they are certain intellectual substances, in neither way could we receive this knowledge, unless our soul derived from itself the knowledge of intellectual being. Consequently we must use the science about the soul’s intelligence as a principle on which to establish all our knowledge about separate substances.

But it does not follow, if by the speculative sciences we are able to arrive at the knowledge of what the soul is, that we are able to arrive at the knowledge of what separate substances are, by means of these sciences: because our intelligence, by which we arrive at the knowledge of what the soul is, is far removed from the intelligence of a separate substance. Nevertheless through knowing what our soul is, we are able to go so far as to know a remote genus of the separate substances: but this is not the same as to understand their substance.

And just as through the soul itself we know that the soul is, inasmuch as we perceive its acts, and seek by a study of its acts and their objects to know what it is, through the principles of speculative sciences: so too, concerning those things that are in our soul, namely its powers and habits, we know indeed that they are, inasmuch as we perceive their acts; but what they are we gather from the nature of these same acts.