The Positive Outcome of Philosophy / The Nature of Human Brain Work. Letters on Logic.

by Joseph Dietzgen

If we apply this metaphysics[1] to our study, the faculty of thought, we see that its functions, like all other things, are material manifestations, which are all equally true. All manifestations of the mind, all ideas, opinions, errors, partake of a certain truth, all of them have a kernel of truth. Just as inevitably as a painter derives all forms of his creation from perceptible objects around him, so are all ideas, images of true things, theories of true objects. So far as perceptions are perceptions, it is a matter of course that all perceptions perceive something. So far as knowledge is knowledge, it requires no explanation that all knowledge knows something. This follows from the rule of identity, according to which a equals a, or from the rule of contradiction, according to which 100 is not 1,000.

All perceptions are thoughts. One might claim, on the other hand, that all thoughts are not perceptions. One might define "perceiving" as a special kind of thought, as real objective thought in distinction from supposing, believing, or imagining. But it cannot be denied that all thoughts have a common nature, in spite of their many differences. Thought is treated in the court of the faculty of thought like all other things, it is made uniform. No matter how different the thoughts I had yesterday may be from those I have to-day, no matter how much the thoughts of different human beings may vary at different times, no matter how clearly we may distinguish between such thoughts as those expressed by the terms idea, conception, judgment, conclusion, impression, etc., they each and all possess the same common and universal nature, because all of them are manifestations of mind.

It follows, then, that the difference between true and erroneous thoughts, between understanding and misunderstanding, like all other differences, is only relative. A thought "in itself" is neither false nor true, it is either of these only in relation to some other object. Thoughts, conceptions, theories, natures, truths, all have this in common that they belong to some object. We have seen that any object is a part of the multiplicity of sense perceptions in the world outside of our brains. After as much of the universal being as constitutes the object which is to be understood has been defined by some customary term of language, truth is to be found in the discovery of the general nature of this perceptible part of being.

The perceptible parts of being which constitute the things of this world have not only a semblance and manifestation, but also a true nature which is given by means of their manifestation. The nature of things is as infinite in number as the world of sense perceptions is infinitely divisible in space and time. Every part of any phenomenon has its own nature, every special phenomenon has its general truth. A phenomenon is perceived in touch with the senses, while the true or essential nature of things is perceived in contact with our faculty of thought. In this way we find ourselves face to face with the necessity of speaking here, where the nature of things is up for discussion, simultaneously of the faculty of thought, and on the other hand of dealing with the nature of things when the faculty of thought is our main subject.

We said at the outset: The criterion of truth includes the criterion of reason. Truth, like reason, consists in developing a general concept, or an abstract theory, from a given sum of sense perceptions. Therefore it is not abstract truth which is the criterion of true understanding, but we rather refer to that understanding as being true which produces the truth, or the general hall-mark of any concrete object. Truth must be objective, that is to say it must be the truth about some concrete object. Perceptions cannot be true to themselves, they are true only in relation to some definite object, and to some outside facts. The work of understanding consists in the abstraction of the general hall-mark from concrete objects. The concrete is the measure of the general, the standard of truth. Whatever is, is true, no matter how much or how little true it may be. Once we have found existence, its general nature follows as truth itself. The difference between that which is more or less general, between being and seeming, between truth and error, is limited to definite conditions, for it presupposes the relation to some special object. Whether a perception is true or false will, therefore, depend not so much on perception as on the scope of the question which perception tries to solve of its own accord or which it is called upon to solve by external circumstances. A perfect understanding is possible only within definite limits. A perfect truth is one which is always aware of its imperfection. For instance, it is perfectly true that all bodies have weight only because the concept of "body" has previously been limited to things which have weight. After reason has assigned the conception of "body in general" to things of various weights, it is no longer a matter for surprise to find that bodies must inevitably have weight. Once it is assumed that the term "bird" was abstracted exclusively from flying animals, we may be sure that all birds fly, whether they are in heaven, on earth, or in any other place. And to explain this we do not require the belief in a priori conceptions which are supposed to differ from empirical conceptions by their strict necessity and generality. Truths are valid only under certain conditions, and under certain conditions errors may be true. It is a true perception that the sun is shining, provided we understand that the sky is not covered by clouds. And it is no less true that a straight stick becomes crooked in flowing water, provided we understand that this truth is an optical one. Truth is that which is common or general to our reasoning faculty within a given circle of sense perceptions. To call within a definite circle of sense perceptions that which is exceptional or special the rule or the general, is error. Error, the opposite of truth, arises when the faculty of thought, or consciousness, inadvertently or shortsightedly and without previous experience concedes to certain phenomena a more general scope than is supported by the senses, for instance when it hastily attributes to what is in fact only an optical existence, a supposed plastic existence also.

The judgment of error is a prejudice. Truth and error, understanding and misunderstanding, knowing and not knowing, have their common habitation in the faculty of thought which is the organ of science. Thought at large is the general expression of experienced facts perceived by the senses, and it includes errors as well. Error is distinguished from truth in that the former assigns to any definite fact of which it is a manifestation, a wider and more general existence than is supported by sense perceptions and experience. Unwarranted assumption is the nature of error. A glass bead does not become a counterfeit, until it pretends to be a genuine pearl.

Schleiden says of the eye: "When the excited blood expands the veins and presses on the nerves, we feel it in the fingers as pain, we see it in the eyes as forked lightning. And thus we obtain the irrefutable proof that our conceptions are free creations of the mind, that we do not perceive the external world as it really is, but that its reflex actions on us simply give rise to a peculiar brain activity, on our part. The products of this activity are frequently connected with certain processes of the external world, but frequently they are not. We close our eyes and we see a circle of light, but there is in reality no shining body. It is easy to see that this may be a great and dangerous source of errors of all kinds. From the teasing forms of a misty moonlight night to the threatening and insanity-producing visions of the believer in ghosts we meet a series of illusions which are not derived from any direct processes of external nature, but belong to the field of the free activity of the mind which is subject to error. It requires great judgment and wide education, before the mind learns to break away from all its own errors and to control them. Reading in general seems so easy, and yet it is a difficult art. It is only by degrees that the mind learns to understand which of the messages of the nerves may be trusted and used as a basis for conceptions. The light, if we consider it entirely by itself, is not clear, not yellow, nor blue nor red. The light is a movement of a very fine and everywhere diffused substance, the ether."

The beautiful world of light and splendor, of color and form, is supposed not to be a perception of something which really is. "Through the thick covering of the grape arbor, a ray of sunlight undulates into the cooling shadows. You think you see the ray of light itself, but what you really see is nothing but a flock of dust particles." The truth about light and color is said to be that they are "waves rushing through ether in restless succession at the rate of 160,000 miles per second." This true physical nature of light and color is supposed to be so illusive, that "it required the sharp intellects of the greatest thinkers to reveal to us this true nature of light. We find that every one of our senses is susceptible only to definite external influences, and that the stimulation of different senses produces different conceptions in our mind. Thus the sense organs are the mediators between the external soulless world (undulations of the ether), which is revealed to us by science, and the beautiful world of sense perceptions in which we find ourselves with our minds."

Schleiden thus gives an illustration of the fact that there is still a great deal of embarrassment, even in our times, when the understanding of these two worlds is under discussion, that there is still much helpless groping to explain the connection between the world of thought, of knowledge or science, which is in this case represented by undulations of the ether, and between the world of our five senses, represented by the bright and colored lights of the eyes or of reality. At the same time this illustration shows how queer the traditional survivals of speculative philosophy sound in the mouth of a modern scientist. The confused condition of this mode of thought is seen in the distinction between "an external sense-perceived world of science" and another one, "in which we find ourselves with our minds." The distinction between the senses and the mind, between theory and practice, between the special and the general, between truth and error, has been noticed by such thinkers, but they have no solution for it. They know there is something missing, but they do not know where to look for it, and therefore they are confused.