The Divine Lamp

  What follows is chapter 2 of Maurice De Wulf’s THE PHILOSOPHICAL SYSTEM OF ST THOMAS AQUINAS.  To read chapter 1, GO HERE.

 How knowledge is formed

Origin of sensations. Psychical and physical aspects: There are two important questions concerning the different kinds of knowledge which consciousness reveals to us: How they are formed and what is their value. These tow questions are quite distinct, and for the subject of what follows. Here we shall discuss how knowledge, whether sensuous or intellectual, comes into existence.

As soon as a child awakens to life, his external senses bring him into contact with something other than his consciousness: the color, taste, shape, resistance, temperature, ect., of material things. Throughout life, sensations continue to play this Principal role. Now, according to the Schoolmen, a sensation necessitates an influx of a particular object known and the reaction of the subject knowing. Let us take the sight of an oak tree as an example. The sense or psychic power of sight does not derive from itself the content of its act of vision. An impulse coming from outside and received by me is an indispensable factor, without which an act of sight would be impossible. But as soon as that impulse coming from the oak tree is received by me, I react to the stimulus, and this vital reaction completes the sense perception. The whole phenomenon is imprinted from outside, and exhibited from inside; it has a passive aspect and an active one. The Schoolmen employed the term species impressa and expressa to signify these two aspects (impression and reaction) relating sensuous knowledge to the object known to the subject knowing.

Thomas insists that this sense perception “is not known directly (id quod cognoscitur). What is present to sense consciousness, what we attain to, is the thing itself- the oak tree. The impression which it produces in me is known only by a reasoning process. We realize why an impulse coming from the external object is the necessary condition by which we know (id quo cognoscitur)- just as nervous activity is needed in sense perceptions and is not perceived by consciousness. Analyzing what actually is, we conclude that something else must be.

The phenomenon which we have just been considering, is wholly psychical, since it takes place completely in us, and is of a cognitive kind. Therefore, the problem of the transmitting medium of sensations is quite distinct from it. By what medium is it that the oak tree, situated at a distance of ten yards, say, from my eye, affects my organism? A few Schoolmen, such as Henry of Ghent, confounded this problem with the previous one. Thomas Aquinas and Duns Scotus, on the contrary, carefully distinguished them. The transmission of the physical action of external objects through the intervening air or water is treated in general accordance with their notions of physics which we need not enter into here.

Origin of intellectual knowledge: There is a well known adage of scholastic and Thomistic psychology, which states that we derive the content of our abstract ideas from the content of our sensations, and, by means of these, ultimately from the material universe. Nihil est in intellectu quod prius non fuerit sensu. “There is nothing in the mind that is not first in the senses.” Our ideas of life, strength, greatness, motion, action exercised or received, double, half, left, right, ect.,- all these and a thousand others equally abstract in nature- are derived from the sense perceptions which surround us. We have proper and direct knowledge of the material world only. Our mind is closely united to our body, and it is in and through the corporeal bodies that we obtain our intellectual knowledge. It follows from this that even moral ideas (justice, right, ect.,) and our knowledge of spiritual beings (the mind, spirits, God) is derived from, and must be expressed in terms of the material, by means of comparison, analogy, negation, and transcendence. We have only an improper and indirect idea of what is spiritual. Although we can prove that there is such a thing as a spiritual being, we do not know in what it consists properly, and our feeble minds have to conceive it by applying to it the notions of being, reality, causality, etc., which have come to us through the channel of our senses.

He problem of the origin of our abstract thoughts, however, is to be solved in the same way in which it is solved for our sensations. But it is more complicated on account of a special difficulty.

Before meeting this difficulty, let us take note of the similarity which exists between the processes of sensation and of thought, and why, in the last analysis, both will be solved in the same way. This similarity consists in the initial impression coming from an external impulse, and followed by a characteristic reaction which belongs to thought as well as sensation.

For, experience and consciousness alike prove that the mind also needs to be determined or completed by the corporeal object known, and that it does not derive merely from itself the content of its ideas. A blind man has no idea of color. Left to itself, our mind would be an empty desert, or a clean slate (tabula rasa), with nothing written on it. Here, as in the case of sensation, there is a passage from potentiality of actuality; there is an initial passive state, and there is an impression which is received (species intelligibilis impressa). The two horses or dollars from which I derive the abstract idea of the number ‘two,’ or ‘money,’ ‘power,’ ‘form,’ ect., act upon my mind. And just as in the case of sensation the mind reacts to the stimulus and answers by a vital act, by means of which the phenomenon of knowledge is completed (species intellibilis expressa).

Now we have to deal with a special difficulty which arises in the case of abstract knowledge. This difficulty appears because it is necessary to harmonize the doctrine of which we have just been speaking with a central doctrine of scholastic metaphysics. Wee shall see later on that the universe of all the schoolmen without exception is a pluralistic one, and that each of the myriad of beings of which it is composed has its own separate and individual existence. Each oak tree possess its own being, independent of all others, and this is equally true of men, animals, ect. And thence comes the difficulty: a particular individual thing, such as an oak tree, can give rise to a sensation of sight which in turn is particularized; but how can it give rise to abstract notions such as life, cylindrical form, without the particularizing conditions which belong to each real living, or cylindrical being? How can this particular living being give rise to the notion of life as such? How can the concrete be known abstractly.

The external object (which we here suppose to exist outside of us) cannot determine thought in the same way as it determines sensation. By itself alone it is powerless. The two horses, being particularized and individual, cannot, by means of the sensations they produce, give rise to an impression in us which gives them a mode of being different in kind and superior (abstract) to that which really belongs to them (particular, concrete). Otherwise we should have a cause producing an effect superior to itself. The less would produce the more. At this point, scholasticism adopts an Aristotelian theory. It is not only the two horses or the two dollars which act upon my intelligence, but the sensation of the two horses or the two dollars act in cooperation with and in dependence upon a special spiritual power within me, which “shines upon the sense data, and makes them capable and ready to produce a knowledge in which reality is deprived of all its concrete and individual features.” This creative power is called active intellect (intellectus agens), and in opposition to it the mind or intelligence in which the impression is produced, under the twofold influence of the corporeal beings and the intellectus agens, is called intellectus possibilis.

It is important to note here as in the case of sensation, that our mind grasps directly, in the two dollars, the content ‘two,’ ‘money,’ ‘paper,’ ect.; but in attaining these notions, we are aware of neither the spiritual power of abstracting, nor of the impressions (species impressa) which it produces in us by the object known. It is again by a process of reasoning, which seeks for an adequate explanation of the phenomenon, that we pass from what is to what must be. This does not imply that by means of this theory we understand the whole mechanism of thought. The latter remains a mystery. In many questions we must be satisfied to know that something exists, even if we cannot penetrate its inmost nature. We must never ask of a theory more than it undertakes to do.  (THE PHILOSOPHICAL SYSTEM OF ST THOMAS AQUINAS, chapter 2, Maurice De Wolf.  Public domain book)