II PURE REASON OR THE FACULTY OF THOUGHT IN GENERAL
When speaking of food in general, we may mention fruits, cereals, vegetables, meat and bread and classify them all, in spite of their difference, under this one head. In the same way, we use, in this work, the terms reason, consciousness, intellect, knowledge, discernment, understanding, as referring to the same general thing. For we are discussing the general nature of the thought process rather than its special forms.
"No intelligent thinker of our day," says a modern physiologist, "pretends to look for the seat of the intellectual powers in the blood, as did the ancient Greeks, or in the pineal gland, as was the case in the middle ages. Instead we have all become convinced that the central nerve system is the organic center of the intellectual functions of the brain." Yes, true enough, thinking is a function of the brain and nerve center, just as writing is a function of the hand. But the study of the anatomy of the hand can no more solve the question: What is writing? than the physiological study of the brain can bring us nearer to the solution of the question: What is thought? With the dissecting knife, we may kill, but we cannot discover the mind. The understanding that thought is a product of the brain takes us closer to the solution of our problem, in as much as it draws it into the bright light of reality and out of the domain of fantasy in which the ghosts dwell. Mind thereby loses the character of a transcendental incomprehensible being and appears as a bodily function.
Thinking is a function of the brain just as walking is a function of the legs. We perceive thought and mind just as clearly with our senses as we do pain and other feelings. Thought is felt by us as a subjective process taking place inside of us. According to its contents this process varies every moment and with each person, but according to its form it is the same everywhere. In other words, in the thought process, as in all processes, we make a distinction between the special or concrete and the general or abstract. The general purpose of thought is understanding. We shall see later that the simplest conception, or any idea for that matter, is of the same general nature as the most perfect understanding.
Thought and understanding cannot be without subjective contents any more than without an object which suggests individual reflection. Thought is work, and like every other work it requires an object to which it is applied. The statements: I do, I work, I think, must be completed by an answer to the question: What are you doing, working, thinking?
Every definite idea, all actual thought, is identical with its content, but not with its object. My desk as a picture in my mind is identical with my idea of it. But my desk outside of my brain is a separate object and distinct from my idea. The idea is to be distinguished from thinking only as a part of the thought process, while the object of my thought exists as a separate entity.
We make a distinction between thinking and being. We distinguish between the object of sense perception and its mental image. Nevertheless the intangible idea is also material and real. I perceive my idea of a desk just as plainly as the desk itself. True, if I choose to call only tangible things material, then ideas are not material. But in that case the scent of a rose and the heat of a stove are not material. It would be better to call thoughts sense perceptions. But if it is objected that this would be an incorrect use of the word, because language distinguishes material and mental things, then we dispense with the word material and call thought real. Mind is as real as the tangible table, as the visible light, as the audible sound. While the idea of these things is different from the things themselves, yet it has that in common with them that it is as real as they. Mind is not any more different from a table, a light, a sound, than these things differ among themselves. We do not deny that there is a difference. We merely emphasize that they have the same general nature in common. I hope the reader will not misunderstand me henceforth, when I call the faculty of thought a material quality, a phenomenon of sense perception.
Every perception of the senses is based on some object. In order that heat may be real, there must be an object, something else which is heated. The active cannot exist without the passive. The visible cannot exist without the faculty of sight, nor the faculty of sight without visible things. So is the faculty of thought a phenomenon, but it can never exist in itself, it must always be based on some sense perception. Thought appears, like all other phenomena, in connection with an object. The function of the brain is no more a "pure" process than the function of the eye, the scent of a flower, the heat of a stove, or the touch of a table. The fact that a table may be seen, heard, or felt, is due as much to its own nature as to that of another object with which it enters into some relation.
But while each function is limited by its own separate line of objects, while the function of the eye serves only for the perception of the visible, the hand for the tangible, while walking finds an object in the space it crosses, thought, on the other hand, has everything for its object. Everything may be the object of understanding. Thought is not limited to any special object. Every phenomenon may be the object and the content of thought. More than this, we can only perceive anything when it becomes the object of our brain activity. Everything is therefore the object and content of thought. The faculty of thought may be exerted quite generally on all objects.
We said a moment ago that everything may be perceived, but we now modify this to the effect that only perceivable things may be perceived. Only the knowable can be the object of knowledge, only the thinkable the object of thought. To this extent the faculty of thought is limited, for it cannot replace reading, hearing, feeling, and all other innumerable activities of the world of sensations. We do, indeed, perceive all objects, but no object may be exhaustively perceived, known, or understood. In other words, the objects are not wholly dissolved in the understanding. Seeing requires something that is visible, something which is, therefore, more than seeing. In the same way, hearing requires something that can be heard, thinking an object that can be thought of, something which is more than our thoughts, something still outside of our consciousness. We shall learn later on how we arrive at the knowledge that we see, hear, feel, and think of objects, and not merely of subjective impressions.