§ 75.
1. At this point of our exposition, it is of chief importance to set forth the relation which Augustine conceives to exist between reason and authority. All that we learn, he says, we learn either from authority or from reason. Faith is the result of the former process, knowledge is the result of the latter. In the order of time authority comes first, in the order of the nature of things, reason is the first and most excellent. The usual course when we learn a thing is that authority comes before reason. Authority offers the truth which faith thereupon accepts, but this process leads on to scientific knowledge. For reason is thus enabled to direct its attention to the truth given by authority, to acquire scientific knowledge of it, and to establish it on a scientific basis. The latter kind of knowledge is of its nature higher than a mere knowledge of faith. In this wise does faith become the basis, the condition, and the first beginning of scientific knowledge (De Ord., Lib. 2, c. 9.)
2. These general principles Augustine applies to determine the relation between Divine Revelation and human reason. In any scientific investigation of revealed truth, faith must precede knowledge, it must be the basis and antecedent condition of knowledge. In other words, the truths of divine revelation must be received by faith before we can attain a scientific or a speculative knowledge of them. Faith is therefore indispensable for man. This the more that sin has entangled man in the love of things of earth, and diverted him from the eternal; and in consequence, faith has become necessary to man as a means of salvation, as the means by which he must reach truth, and thus attain salvation (De Vera Relig., c. 24).
3. This being premised, we may now take up the theory of knowledge, strictly so called, which Augustine offers us. To every act of knowledge, he teaches, two factors concur -- an object known, and a subject knowing. Of its nature, the object is antecedent to the subject -- without an object no knowledge is possible. This principle is of universal application. Now, the objects of knowledge are of two kinds, the sensible and the supersensuous; we may, therefore, distinguish in man two kinds of knowledge -- experience and reason. Sense, or experience, is concerned with the sensible; reason deals with the supersensuous or intelligible. These two kinds of knowledge are essentially distinct from one another.
4. But the question arises: Is certainty possible in knowledge? The Academics deny this, inasmuch as they teach that mere probability is all that we can attain. But, in the first place, such probability could not be had unless we suppose the knowledge of truth possible, for the probable is probable only because it is like truth; and it is measured by comparison with truth. In the next place, probability would not, by any means, suffice to make us happy, whatever the Academics may say to the contrary. For, no one can be happy who does not possess that which he desires to possess, and no one searches who does not wish to find. He, therefore, who seeks truth without finding it, does not possess that which he wishes to possess, and cannot, consequently, be happy. Nor can such an one be said to be really wise; for the sage, as such, must be happy; certainty in knowledge must, therefore, be attainable.
5. The same principle can further be established by positive argument. We cannot doubt that we are thinking, willing, and living. Consciousness gives such indisputable evidence on this point that doubt or denial is impossible. If a person were to doubt whether he thinks or exists, he would, by his very doubt itself, admit that he thinks and exists; if he did not exist, he could not doubt. Furthermore, the man who knows that he doubts, has, by the fact, knowledge of a truth; is certain of this truth, that he is doubting. The man who doubts whether there is any truth, acknowledges one proposition to be true; and, as all things are true only because truth exists, he, by the fact, acknowledges the existence of truth and his own certainty with regard to it (De Lib. Arb., Lib. 2, c. 3. Soliloq., Lib. 2, c. 1, etc.)
6. Again, the truth of our sensuous knowledge is also beyond doubt. We may, indeed, be deceived in the use of our senses; but the fault is not to be attributed to the senses, for these always represent the object, according to the impressions which they actually receive. It is not by our senses we are deceived, but by the judgment we form with regard to their perceptions. We form our judgment hastily on our present impressions, without closer inquiry into the relations which may possibly exist between these and external objects. As for the existence of an objective material world, sense renders us so certain that doubt is wholly impossible.
7. The truth of sensuous knowledge cannot be doubted; the truth of knowledge gained by intellect is no less above suspicion. Nothing can be more absurd than to assert that what we see with our eyes exists, but what we perceive with our intellect does not exist; for it would be irrational to suppose that reason or intelligence is not incomparably higher than bodily sense (De Immort. Anim., c. 10). Dialectical truths are, therefore, indisputable. No one, for instance, can doubt that the truth of the antecedent of an hypothetical proposition involves the truth of the consequent, or that, in a disjunctive proposition, the denial of all the members, except one, involves the truth of the member remaining. And so of other truths.
8. As to the possibility of attaining certain knowledge, there can, then, be no doubt. A further question now arises as to the conditions. of intellectual knowledge; and, first, as to the way in which intellectual knowledge is acquired. Augustine distinguishes two methods by which the knowledge of intelligible objects is attained. The first method begins with the faculties of sense. The intellect directs its attention to the objects perceived by the senses, inquires into their causes, and thus endeavours to reach the knowledge of the Ultimate, or First Cause, a process described in the words of the Apostle "Invisibilia Dei per ea quae facta sunt intellecta conspiciuntur" (De Gen. ad litt., iv, c. 32).
9. The second method begins with what is within man himself. Man must withdraw from sense, and retire within himself, if he would contemplate truth in all its purity. Augustine reminds us of this principle at every turn. "Noli foras ire," he repeats, "in te redi; in interiori homine habitat veritas" (De Vera Relig., c. 39). The consideration of himself and of the processes of his intellectual life is, for man, the second means to the knowledge of higher truth. And this way is the more excellent, for it is more within man's reach, and therefore leads more perfectly to the end pursued than the other, which begins with sense and leads to the supersensuous.
10. To enable man by these means successfully to reach intelligible truth another condition is necessary. This condition is virtue and purity of heart. Truth can find place only in a pure heart. The man who would successfully prosecute the search after truth must, therefore, purify his soul from all defilement, and the purer his heart is from sin, and the more it is adorned with virtue and holiness, the more clearly and more perfectly will truth be communicated to him.
11. This being premised, we may now penetrate more deeply into the nature of intellectual knowledge. The question which first arises concerns the ultimate or highest ground of all knowledge. Augustine answers that the ultimate ground or reason of all intellectual knowledge is the Absolute Truth -- God. This principle Augustine proves after the fashion of Plato:
(a.) That we may have knowledge of anything as true, or good, or beautiful, and distinguish it from what is not true, or good, or beautiful, it is necessary to have a rule or standard, according to which the judgment regarding the object is determined. This standard, according to which we estimate the truth, or goodness, or beauty of an object, must be absolutely immutable, otherwise it could not be a trustworthy standard of judgment. The standard of judgment must be present to our minds; but, it is not the mind itself, for the mind is changeable, and, besides, we judge ourselves and our own actions by this standard, and must so judge ourselves. That immutable, invariable standard must, therefore, be something higher than our own minds; and, since there is nothing immutable and invariable but God, this standard, must be God Himself, in so far as He is absolute truth, goodness, and beauty (De Lib. Arb., II, c. 12, 16).
(b.) If a human teacher states any principle to us, we do not immediately perceive the truth of the principle. We must have within ourselves a criterion by which we test the truth of the proposition stated. And this criterion can, for the reason already given, be no other than the absolute truth itself. It appears, then, that the immutable, eternal Word of God is the teacher of the soul; we consult this Word when we endeavour to assure ourselves of the truth of a proposition laid down by a human teacher; and this truth the Word reveals to us with as much clearness and evidence as our moral condition permits. Instruction from without only leads us to consult the instructor within ourselves, to receive from Him an insight into the truth (De Magistro, c. 11).
(c.) When two individuals understand and acknowledge as true an assertion advanced by one or the other, the question presents itself: How and by what means have both alike knowledge of the truth in question? The one does not read it in the other; there must be some common ground in which and by which both alike obtain knowledge of it. This ground can, again, be no other than the absolute, immutable truth, which is above both, and in accordance with which both alike form their judgment (Conf. XII, c. 25).
12. It follows from these considerations that our minds are, in some mysterious way, united to the eternal unchanging truth. Without this union they would be incapable of attaining knowledge of truth. God is the Sun which illumines human minds. In His light we perceive truth. As we can observe nothing with the eye of the body, when the sun does not shed its light over the objects of vision; so we cannot have knowledge of intellectual truth except in the light of God -- the Sun of our faculty of intelligence. And, as the sun sheds its light upon all men, so that, in its light, all may be able to see, so does God give His light to all minds to make truth accessible to all. This gift is, however, bestowed upon different men in different degrees, as their aptitudes are differently determined by their moral condition.
13. The knowledge of the essences of created things depends upon the intellectual light thus furnished by the absolute divine truth. Without this light such knowledge would be impossible. The Divine Word includes within Himself the ultimate reasons (rationes) or archetypal forms, after which all things are created and of which all things are ectypes. God, as absolute truth, is thus the ultimate cause of all our knowledge of truth, and the Word of God is the ultimate cause which renders intelligible to us the essences of things, inasmuch as He includes within Himself the archetypal forms of all existence. It follows that we may assert, and must assert, that we have knowledge of the essences of things in their ultimate eternal causes (in rationibus aeternis) which exist in God.
14. In this way the origin of our intellectual knowledge must be explained. It now becomes manifest how the consideration of our own activity of intellect leads us at once to the knowledge of God. When we see that all intellectual knowledge is dependent upon the absolute truth, which is the sun of our intelligence, we need only turn our gaze from the object illumined by that sun to the sun itself, and we, at once, have knowledge of God, the ultimate and supreme cause of all our knowledge.
16. If we consider the theory of knowledge here set forth, we shall observe that Augustine follows unmistakably the Platonic line of thought. But we should not be warranted in concluding, at once, from this, that his views are identical with those of the Ontologists. Augustine nowhere asserts that we have immediate intuition of God and of all truth in Him -- the position maintained by the Ontologists. Nay, such a thing would be in flat contradiction with his subsequent teaching regarding God and created things. The later scholastics, it may be assumed, interpret him correctly, when they understand Augustine's theory, which holds that God is the sun of the mind, and that we have knowledge of truth only in the light which He diffuses, to mean that God is the ultimate principle, not of all being only, but of all knowledge as well; that the intellect, by which we attain the truth, is a participation of the Divine intelligence; that, moreover, the principles of reason which guide our judgments have their ultimate and highest source in God (in the Divine Word), and that, when we judge in accordance with these principles, we are judging according to the standard fixed by the Absolute Truth. We may also assume the Scholastics to be warranted in maintaining that Augustine's proposition as to our knowing the essences of things in rationibus aeternis does not imply an immediate contemplation of the Divine Ideas, but merely signifies that the essences of things could neither be nor be known, unless they were antecedently formed in the Divine Ideas, as in their highest cause. The thoroughly Platonic character of Augustine's theory of knowledge lent favour, however, to the interpretation put upon it by the Ontologist school at a later period.