7. ARE THERE ANY LIMITS TO KNOWLEDGE?
7.0 Cognitive Unity
 WE have established that the elements needed to explain reality are to be found in the two spheres of perception and thought. As we have seen, it is due to our organization that the full, total reality of things (including our own self as subject) appears at first as a duality. Cognition overcomes this duality by combining the two elements of reality: the percept and the concept worked out by thinking, into the complete thing. Let us call the way the world presents itself to us before it has taken on its true nature by means of cognition, "the world of appearance," in contrast to what has been put together out of percept and concept to form a single unity. We can then say, the world is given to us as a duality (Dualism), and cognition works upon it to bring about a unity (Monism). A philosophy that starts from this fundamental principle can be called a Monistic philosophy, or Monism. Opposed to this is the two-world theory, or Dualism. Dualism does not assume that there are two sides of a single reality that are held apart by our organization, but that there are two worlds completely different from each other. It then tries to find in one of these two worlds the principles of explanation for the other.
 Dualism rests on a misunderstanding of what we call knowledge. It divides the whole of reality into two realms, each with its own laws, and it leaves these two worlds standing outside one another.
 The distinction between the object of perception and the thing-in-itself, introduced by Kant into scientific thought and never since removed from it, stems from this kind of Dualism. Our discussion has shown that it is due to the way our mental organization functions that a particular (separate) thing can be given to us only as a perception. Thinking then overcomes this separation by assigning to each percept its lawful place in the world-whole. As long as we designate the separated parts of the world-whole as percepts, we are simply following in this act of separating-out a law of our subjectivity. If, however, we consider the sum-total of all percepts as one part, and place it over against a second part, the things-in-themselves, then our philosophizing loses all foundation. We are simply playing with concepts. We construct an artificial contrast, but can find no content for the second part, because the content for a particular thing can only be drawn from perception.
7.1 Facts Of Experience and Hypothetical World Principle
 Every kind of reality that is assumed to exist outside the realm of perception and conception must be assigned to the limbo of unverified hypotheses. The “thing-in-itself” belongs in this category. It is not surprising that the Dualistic thinker is unable to find a connection between his hypothetically-assumed world principle and the facts given in experience. A content can be found for his hypothetical universal world principle only by borrowing it from the world of experience and then deceiving oneself that this is not the case. Otherwise it remains an empty and meaningless concept, a mere form without content. The Dualistic thinker’s usual reply to this is: the content of this concept is inaccessible to our knowledge; all we can know is that such a content must exist, but not what it is. In both cases it is impossible to overcome dualism. Even if one brings a few abstract elements from the world of experience to provide a content for the concept of the thing-in-itself, it still remains impossible to explain the rich, concrete life of experience on the basis of a few characteristics that themselves are only borrowed from experience. Du Bois-Reymond states that the non-observable atoms of matter give rise to sensation and feeling by means of their position and motion, and then infers from this premise that we can never find a satisfactory explanation of how matter and motion produce sensation and feeling, for:
“it is, and will forever remain, entirely incomprehensible that a number of atoms of carbon, hydrogen, nitrogen, oxygen, etc., should be other than indifferent as to how they lie and move in the present, how they lay and moved in the past and how they will lie and move in the future. It cannot in any way be conceived how consciousness can come into existence through their interaction."
This conclusion is characteristic of the tendency of this entire orientation of thought. Position and motion are abstracted from the rich world of percepts. These are carried over and applied to an imagined world of atoms. And then the thinker is astonished to find that he cannot develop real life out of this self-made principle borrowed from the world of perception.
 That the Dualist cannot arrive at an explanation of the world, working as he does with a completely empty concept of the "in-itself," follows from the very definition of his principle given above.
 In every case the Dualist feels compelled to set insurmountable limits to our cognitive capacity. The adherent of a Monistic world-view knows that everything he needs to explain any given world phenomenon is to be found within this world itself. What prevents him from reaching an explanation can only be chance limitations in time and space, or defects of his bodily or mental organization. Not deficiencies of the human organization in general, but of his particular, individual organization.
7.2 "I" Answers Its Questions
 It follows from the concept of knowledge, as we have defined it, that one cannot speak of limits to knowledge. Cognition is not a concern of the universe as such, it is something the human being has to settle for himself. Things do not demand explanations. They exist and act on each other according to laws that thinking can discover. They exist in inseparable unity with these laws. Our ‘I’-nature encounters the things and, to begin with, only grasps that side of them we have called percepts. But in the interior of this ‘I’ we find the power that enables us to discover the other part of reality as well. Only when the ‘I’-nature has combined for itself the two elements of reality that are inseparably united in the world, is our thirst for knowledge satisfied. The ‘I’ is then again in contact with reality.
 The preconditions necessary for an act of knowledge to take place exist through and for the ‘I’. The ‘I’ sets itself questions to which it seeks answers. It draws questions from the elements of thought that are perfectly clear and transparent in themselves. If we ask ourselves questions that we cannot answer, then the content of the question must not be clear and intelligible in all its parts. It is not the world that poses questions to us; we pose them to ourselves.
 I can imagine finding myself unable to answer a question that I happened to see written down somewhere without knowing the universe of discourse from which the content of the question was taken.
7.3 Reconcile Well-Known Percepts and Concepts
 Our cognition involves questions that arise for us through the fact that a sphere of percepts conditioned by factors of place, time, and our subjective organization, confronts a sphere of concepts expressing the world as a unity. My task is to reconcile these two spheres, both of which are very well-known to me. There is no room here to speak of limits to knowledge. It may be that at a particular moment this or that remains unexplained because we are prevented by chance circumstances from perceiving the things involved. But what is not found today may be found tomorrow. These are only temporary limits and can be overcome with further progress in perception and thinking.
7.4 Conceptual Representation Of Objective Reality
 Dualism makes the mistake of transferring the opposition of subject and object, which has significance only within the perceptual world, onto pure conceptual entities outside this world. Now the distinct and separate things within the perceptual field remain separated only as long as the perceiving subject refrains from thinking. For thinking cancels all separation showing it to be due to purely subjective factors. Therefore the Dualist is really transferring abstract determining factors to entities behind the perceptual world that have, even there, no absolute validity but only a relative validity. By doing this he divides the two factors involved in the cognitive process, percept and concept, into four: (1) the object-in-itself; (2) the percept which the subject has of the object; (3) the subject; (4) the concept which relates the percept to the object-in-itself. The relationship between the subject and the object is "real"; the subject is really (dynamically) influenced by the object. This real process does not appear in our consciousness. But it evokes in the subject a response to the stimulation from the object. The result of this response is the percept. Only this enters our consciousness. The object has an objective reality (independent of the subject), while the percept has a subjective reality. This subjective reality is referred by the subject to the object. This reference is said to be ideal (conceptual). With this the Dualist divides the cognitive process into two parts. One part, the production of the perceived object out of the thing-in-itself, is said to take place outside our consciousness. The other part, the combining of the percept with the concept and referring the result to the object, is said to take place within our consciousness.
Given these assumptions, it is clear why the Dualist believes his concepts are only subjective representations of what is there prior to his consciousness. The objectively real process in the subject through which the percept comes about, and, even more so, the objective relationships between things-in-themselves, remain for such a Dualist unknowable in any direct way. In his view the human being can only construct for himself conceptual representations that do no more than represent what is objectively real. The bond of unity among things, that connects things with one another and also objectively with the individual mind of each of us (as thing-in-itself), lies beyond our consciousness in a Divine Being-in-itself, of which we can have in our consciousness no more than a conceptual representation.
7.5 Real Principles in addition to Ideal Principles
 The Dualist thinks that the whole world would dissolve into a scheme of abstract concepts if he did not insist on "real" connections between things besides the conceptual ones. In other words, the ideal principles discovered by thinking are too airy and insubstantial for the Dualist, so he seeks, in addition, real principles by which to support them.
 Let us examine these “real principles” more closely. The naive person (Naive Realist) regards the things he experiences in the external world as real. The fact that he can grasp these objects with his hands and see them with his eyes is for him valid proof of their reality. “Nothing exists that cannot be perceived” can be said to be the first axiom of the naive person; and its reverse form is accepted to be equally valid: “Everything that can be perceived is real.” The best evidence of this statement is the naive person's view on immortality and ghosts. He imagines the soul as consisting of an extremely fine material substance, which under certain conditions can become visible even to the ordinary person (naive belief in ghosts).
 Compared to his "real world," everything else for the naive realist, especially the world of ideas, is unreal, it is “merely ideal.” What we add to things by way of thinking activity are mere thoughts about things. Thought adds nothing real to our perceptions.
 What is more, the naive person holds sense perception to be the sole evidence of reality, not only for the nature of things, but also for events (processes). In his view, one thing can only affect another when an actual sense-perceptible force goes forth from the one and acts upon the other. Ancient Greek philosophers, who were Naive Realists in the best sense of the word, held a theory of vision by which the eye sends out feelers that touch the objects. Earlier physicists thought that very fine substances stream out from objects and enter the soul through our sense organs. The actual seeing of these substances was said to be impossible only because of the crudeness of our senses compared with the fineness of the substances. In principle, these substances were granted reality for the same reason one grants it to the objects of the sense world, namely, because their kind of existence was thought to be analogous to that of sense-perceptible reality.
7.6 Real Evidence Of Senses in addition to Ideal Evidence
 For the naive mind, the self-contained nature of the experience of Ideas is not considered to be real in the same way as what can be experienced through the senses. An object grasped in “mere idea” remains nothing more than a figment of the imagination until sense-perception can provide proof of its reality. To put it briefly, the naive person demands, in addition to the ideal evidence of his thinking, the real evidence of his senses. This need of the naive person is the reason why belief in revelation arose. The God who is given through thought remains no more than a God we have conjured up in thought. The naive mind demands that God should manifest Himself in ways accessible to sense-perception. God must appear in the flesh, and must prove his Divinity by changing water into wine in a way that can be verified by sense-observation.
 Even cognition, the activity of gaining knowledge, is thought of by the naive person as a process analogous to sensory processes. Things make an impression on the mind, or they project image-copies of themselves that enter through our senses, and so on.
 All that the naive person can perceive with his senses he regards as real, and what he cannot perceive in this way (God, soul, knowledge, etc.) he imagines as being analogous to the objects of perception.
 A science based on Naive Realism would have to consist solely of an exact description of the content of perception. Concepts are for the Naive Realist only a means for achieving this goal. They are there to create conceptual counterparts to the things perceived. They mean nothing for the things themselves. For the Naive Realist only the individual tulips that are seen, or could be seen, count as real. The universal Idea of 'tulip' is to him an abstraction, an unreal thought-picture that the mind constructs for itself out of the characteristics common to all tulips.
7.7 Ideal Entities in addition to Vanishing Perceptions
 The fundamental principle of naive realism, that everything real is perceptible, is refuted by experience, which teaches us that the content of perceptions is transitory. The tulip I see is real today, in a year it will have vanished completely. What persists is the species "tulip." But, for the Naive Realist, this species is “only” an Idea, not a reality. Thus this worldview finds itself in the position of seeing its realities arise and then perish, while what it regards as unreal is more enduring than the real. In addition to percepts, The Naive Realist has to acknowledge the existence of something Ideal. He has to include entities that cannot be perceived with the senses. To avoid contradicting himself he conceives the form of existence of these entities to be analogous to that of sense-perceptible objects. These hypothetical realities are the invisible forces through which sense-perceptible things act on one another. One such thing is heredity, which has effects that survive the individual, and is the reason why there develops out of the individual a new one that is similar to it, whereby the species is maintained. The soul, the life-principle permeating the bodily organism, is another such reality for which the naive mind always forms a concept on the pattern of sense realities. And finally so, too, the Divine Being is conceived by the naive mind as such a hypothetical entity. The Deity is thought to act in a way that exactly corresponds to the way a human being is seen to act. The Deity is thought of anthropomorphically.
 Modern physics traces sense impressions back to processes in the smallest parts of the body and in an infinitely fine substance, the ether—or something similar. For example, what we sense as warmth is, within the space occupied by the warmth-giving body, the movement of its parts. Here again something imperceptible is thought of by the analogy of something perceptible. The sense-perceptible analogy to the concept “body” might be, according to this way of thinking, the interior of a room shut in on all sides, in which elastic balls are moving in all directions, colliding with one another, bouncing on and off the walls, and so on.
7.8 Imperceptible Reality in addition to Perceptible Reality
 Without assumptions of this kind, the world of the Naive Realist would disintegrate into a disconnected and unrelated chaos of percepts that does not come together to form a unity. Naive Realism can only make these assumptions by being inconsistent in its thinking. If it remained true to its fundamental principle: only what is perceived is real, then it would not assume the existence of something real where it perceives nothing. The non-perceivable forces sending out their effects from perceivable things are, in fact, unjustified hypotheses from the standpoint of Naive Realism. Because Naive Realism knows of no other realities, it endows its hypothetical forces with perceptual content. It applies a form of existence (perceptual existence) to a realm where sense perception—the only means that can provide any evidence of this form of existence—is lacking.
 This self-contradictory worldview leads to Metaphysical Realism. This view constructs, in addition to perceptible reality, an imperceptible reality that is thought of on the analogy of the perceptible one. Consequently, Metaphysical Realism is, of necessity, Dualistic.
 Wherever the Metaphysical Realist observes a relationship between perceptible things (when two things move towards each other, when an external object enters consciousness, etc.), there he assumes a reality. But the relationship that he notices can only be expressed by means of thinking; it cannot be perceived. What is an ideal relationship is arbitrarily made into something similar to a perceptible one. So for this way of thinking the real world consists of perceptible objects that are in an endless process of becoming, arising and then disappearing, and of imperceptible forces that produce them and are the things that endure.
7.9 Monism: Sum of Perceptions and Laws of Nature
 Metaphysical Realism is a self-contradicting mixture of Naive Realism and Idealism. Its hypothetical forces are non-perceptible entities with the qualities of perceptions. The Metaphysical Realist has decided to acknowledge—in addition to the realm for whose form of existence he has a means of knowledge in sense-perception—another realm for which this means of knowledge fails him as it can only be known through thinking. But at the same time he cannot make up his mind to recognize the form of existence that thinking conveys to him, the concept (the Idea), as a factor that is valid on an equal basis with perceptions. If one is to to avoid the contradiction of imperceptible percepts, then it must be admitted that the relationships which thinking establishes between the percepts can have no other form of existence for us than that of the concept. When we reject the invalid part of Metaphysical Realism, the world is seen as a sum of percepts and their conceptual (ideal) relationships. Metaphysical Realism then arrives at a worldview that requires for the percept the principle of perceivability, and for the relationships between percepts the principle of conceivability. This view of the world has no room for the existence of a third realm, besides the perceptual and conceptual world, for which both principles – the so-called "real" principle and the "ideal" principle – are valid.
 When the Metaphysical Realist claims that, in addition to the ideal relationship between the perceived object and the perceiving subject, there must also be a relationship that is 'real' between the “thing-in-itself” of what is perceived and the “thing-in-itself” of the perceptible subject (the so-called individual mind), then his claim is based on the false assumption of a real process that is similar to a process in the sense-world, but non-perceivable. When the Metaphysical Realist goes on to say: I have a conscious, ideal relationship with my world of perceptions; but I can have only a dynamic relationship (of forces) with the real world—he then repeats the mistake we have already criticized. One can talk of a relationship between forces only within the world of perceptions (in the area of the sense of touch), but not outside it.
 Let us call the worldview we have just described, into which Metaphysical Realism merges when it discards its contradictory elements, Monism, because it combines one-sided Realism and Idealism to form a higher unity.
 For Naive Realism the real world consists of a sum of perceptible objects (percepts). For Metaphysical Realism, not only perceptible objects but also imperceptible forces are real. Monism replaces forces with ideal connections obtained by means of thinking. These connections are the laws of nature. A law of nature, after all, is nothing but the conceptual expression of the connection between certain percepts.
7.10 Separation and then Reunion of Self into World Continuum
 The Monist never has any need to look for principles other than percept and concept in order to explain reality. He knows that there is no reason to do so in the whole field of reality. He sees in the perceptual world, as it appears immediately to our perceiving, one half of the reality. He finds the full reality by uniting this world with the world of concepts.
The metaphysical realist may object to the monist: "It may be the case that for your own organization your knowledge is complete within itself, that it lacks nothing; but you do not know how the world appears to a mind organized differently from your own." The Monist would reply: "Maybe there are intelligences other than human; and maybe their percepts are configured differently from ours, if they have perception at all. But this is irrelevant to me for the following reasons."
Through my perception—in fact, through this specifically human way of perceiving— I, as subject, am confronted with the object. This causes the connection of things to appear broken. The subject re-establishes this connection through thinking. In doing so it integrates itself into the context of the world as a whole. As it is only through the Self, as subject, that what is a whole appears split in two along a line between our perception and our concept, so it is the union of these two factors that will give us true knowledge. For beings with a world of perceptions that had a different appearance (if, for example, they had twice as many sense-organs), the continuum would appear broken in another place, and the restoration would take a form specifically adapted to those beings. The question of limits to knowledge exists only for Naive and Metaphysical Realism; they both see in the content of the psyche only ideal representations of the real world. For them, the world outside the subject is something absolute, a self-contained whole, and the subject's mental content is a picture of it, completely external to this absolute. Here, the quality of knowledge depends on the degree of similarity between the representation and the absolute object. A being with fewer senses than man will perceive less of the world, one with more senses will perceive more. As a consequence of perceiving less of the world the former's knowledge will be less perfect knowledge than the latter's.
 For Monism the situation is different. The form in which the world continuum appears to be torn apart into subject and object is determined through the organization of the perceiving being. An object is not something absolute; it is only relative to the nature of the particular subject that perceives it. The bridging of the gap can therefore take place only in a very specific way that is characteristic of the particular human subject. As soon as the Self—which is separated from the world in the act of perceiving—integrates itself back into the world continuum through thinking investigation, then all further questioning ceases, since it was only a consequence of the separation.
 A differently constituted being would have a differently constituted cognition. Our own cognition is sufficient to answer the questions that result from our own mental constitution.
 The Metaphysical Realist must ask, What is it that gives us our percepts? What is it that stimulates the subject?
 For the Monist the way a percept is seen is determined by the subject. But in thinking the subject has the instrument for transcending this self-produced determination.
7.11 Inductive Reasoning: Infer Underlying Causes From Sum of Effect
 The Metaphysical Realist faces a further difficulty when it comes to explaining the similarity between the worldviews of different individuals. He has to ask himself, "Why is it that the theory of the world that I build up out of my subjectively determined percepts and out of my concepts, turns out to be the same view that another individual builds up out of his equally subjective factors? How can I, from my own subjective view of the world, draw any conclusions about the subjective view of another person? The Metaphysical Realist believes he can conclude that the reason people's subjective view of the world are similar stems from their ability to deal with and reach an understanding with one another in practical life. From this similarity of worldviews he then further concludes the similar nature of individual minds, meaning by "individual mind" the "I-in-itself"underlying each subject.
 This kind of conclusion infers, from a sum of effects, the character of their underlying causes. We believe that by observing a sufficiently large number of cases, we can know the situation well enough to be able to predict how the referred causes will behave in other cases. We say that a conclusion of this kind has been arrived at by inductive reasoning. If further observation yields something unexpected, we will find ourselves forced to modify our conclusions, because they are based solely on the particular details of earlier observations. Nevertheless, despite these limitations the Metaphysical Realist maintains that this conditional knowledge of causes is perfectly adequate for practical life.
 Inductive reasoning is the fundamental method of modern Metaphysical Realism. There was a time when it was thought one could develop something out of concepts that was no longer a concept. It was thought that the metaphysical reals, which Metaphysical Realism after all requires, could be recognized through concepts. This method of philosophizing is now a thing of the past. Instead it is thought that from a large enough number of perceptual facts one can infer the character of the thing-in-itself underlying these facts. Just as in the past one tried to derive the metaphysical from concepts, so today the Realist tries to derive it from perceptions. Since concepts are before the mind in transparent clarity, it was thought that the metaphysical, too, could be drawn out of them with absolute certainty. Percepts are not there for us with the same transparent clarity. Each successive percept of a kind is always a little different from the previous ones. In principle, anything inferred from past experience is somewhat modified by each following experience. Since it is subject to correction by future cases, the character of the metaphysically real obtained in this way can only be relatively true. This methodical principle characterizes the Metaphysics of Eduard von Hartmann. This is expressed in the motto he gave on the title-page of his first major work: “Speculative results gained by the Inductive Method of Natural Science.”
7.12 Objective Real World Continuum in addition to a Subjective World Continuum
 The form that the modern Metaphysical Realist gives to his things-in-themselves is arrived at through inductive reasoning. His deliberations concerning the process of cognition has convinced him of the existence of an objectively real world continuum, in addition to the “subjective” world continuum we come to know by means of percepts and concepts. He believes he is able to determine the nature of this objective reality by drawing conclusions inductively from his percepts.