A Beginner's History of Philosophy, Vol. 2: Modern Philosophy

by Herbert Ernest Cushman

The Place of Synthesis in Knowledge. What position does synthesis occupy in the total process of knowledge? Is synthesis one of the factors or elements of knowledge? Is synthesis on the same level with the sensations, the feelings, the imaginations? No, it is very different. The synthesis that Kant is describing isnot the product or conclusion from an inference. Kant does not mean by synthesis the combination of facts as a result, such as a biologist might make in framing the law of the habits of animals from his observation of them. The synthesis that Kant is talking about is not so much the result of combining experiences as the act of combining them. The frame of the unified manifold, the law of its unification, the act of binding the isolated experiences together is synthesis. Synthesis occupies a higher level than the elements of knowledge or knowledge itself. Synthesis is the knowing process rather than the known product. It is constitutive; it is creative; it conditions experience and puts the material of experience together. It must not be thought to be a voluntary act of the mind, which the mind will or will not do, as it pleases. When the mind acts, it synthesizes.

Furthermore, the synthetic functioning of all human minds everywhere is the same. However much their sensations differ, they combine and orderly arrange their sense-materials in the same ways. The synthesis of the human mind is the source of the universality belonging to knowledge; the sensations, the “given,” are the source of the difference in knowledge. Knowledge is the result of minds that function in absolutely the same ways; and we should never have knowledge if the order and linkage of the world depended on the accident of experience. Take, for example, such laws as those of mathematics or the physical law of cause. These are the same for everybody. They are universal laws. The ordinary conception of them as independent principles of an independent nature world will not account for their necessity for everybody and their universality. As independent principles they would differ for different peoples justas sensations differ. In that case we should have no knowledge. Human beings could not then think about the same things, nor reason under the same guiding principles. However, we do think alike, we have the same geometry, the same physical laws, the same time-estimates; and simply because we function alike synthetically. Knowledge is thus the common possession of humanity because the synthetic functioning of the different individual men is identically the same.

A very good way to get at Kant’s central principle of synthesis is to draw this picture. Suppose that besides the race of human beings with its own peculiar way of ordering its world, there were a race of angels endowed with its own powers, another of hobgoblins likewise endowed with its own powers, and so on to x, y, and z races—any number you please. What would be the situation? In the first place, each one of the groups would be absolutely isolated from each of the others. No one would have the power to know even the existence of the others. No one race would even have anything in common with the others. The world of each would be different. In the next place each would be trying to interpret reality, and in doing so, each would construct and order a world of reality of its own. The members of each race would have a world in common and the members would know one another. But that is all. The members of each race would not be able to get outside their own powers of synthesis. In Holy Writ the home of the angels has been sometimes described as having no time and space, but this means only that space and time are aspects of our mental synthesis and not of theirs. We live in our world of our interpretative construction of reality, and they in theirs. The same wouldhave to be said of x, y, and z. None would live in a world of absolute reality. But each would live in a world made different from all the other worlds by the differing mental powers of each race. Yet the members of each race would inhabit a world in common because the individuals of each had common mental powers. The particular world that human beings inhabit is called physical nature, whose laws are known as the laws of science. How can it be one world in which so many millions of different human beings live? Because these millions of human beings are under the same fundamental rational laws, and they construct the world in a common fashion. The laws of nature are, after all, the laws of our own minds. They are the laws of reason. The laws of nature are not the laws of absolute reality, but the laws of the human interpretation of reality. All the linkage of facts, all the law and order of our universe, all the combination of the variety of objects of knowledge—in a word, the entire body of science or the world of physical nature is a human mental synthesis. Does independent absolute reality exist? Yes; but it exists behind the scenes for us as for the angels. Mental synthesis is constitutive of the world in which we are actually engaged—mental synthesis is shot through and through all our experiences. Mental synthesis is the framework of the universe, and therefore Kant says, “The world is my representation.”

The Judgments Indispensable to Human Knowledge. It will be seen from the above discussion that Kant does not believe that an idea or a sensation taken by itself constitutes knowledge. Knowledge consists of sensations framed together in a synthesis. That is, ideas must be taken together with other ideas. This iscalled in grammar a proposition, having a subject and a predicate. In logic it is called a judgment. The only way a human being can express knowledge is in the form of judgments, but all judgments of human beings are not necessarily knowledge.

Judgments are divided by Kant into two large classes,—analytic and synthetic. The large class of analytic judgments are not expressions of knowledge. What is an analytic judgment? An analytic judgment merely expresses in the predicate something that is contained in the usual meaning of the subject. Such a judgment articulates the meaning of an idea by emphasizing some of its well-known attributes. Thus we say, “Gold is yellow.” Such a statement about “gold” does not show any knowledge. It is called sometimes an explicative statement. It is tautologous, but not on that account trivial. Let us look then to synthetic judgments to see if they express knowledge. But first, what is a synthetic judgment? A synthetic judgment is one in which the predicate is not contained in the usual meaning of the subject. It is a statement of something new about the subject in hand. For example, the judgment, “The watch is yellow” is a synthetic judgment because the predicate “yellow” is not a necessary part of the meaning of “watch.” A synthetic judgment therefore brings two ideas together in a new relation. It thereby enriches knowledge and is the expression of discovery. The synthetic judgment is often called ampliative. (The double meaning which Kant gives the term “synthetic” need not confuse us. Synthesis is used by Kant to mean the framing constitution of the mind, and also as one of the results of the activity of the mind, i. e. a class of judgments. In the first sense alljudgments, both analytic and synthetic, are expressions of synthesis.)

Are all synthetic judgments expressions of knowledge? Kant replies that they certainly are not. He points out that there are two classes of synthetic judgments: one class he calls a posteriori and the other a priori. By a posteriori he means judgments founded in some sense-perception, which are particular judgments or judgments that are inferences from a greater or less induction of sense-perceptions. For example, if I say, “To-day is warm,” or that “Swans, so far as I have observed, are white,” I am making a synthetic judgment, because I am joining two ideas in a new relation, and I am also making an a posteriori judgment, because it is a statement founded upon sense-perception. Now Kant rules such judgments out from those that constitute true knowledge. This would rule out even empirical generalizations of high probability, such as “The sun rises in the east.” A posteriori judgments, or those founded on experience, however large, do not give us knowledge, but merely probability. The cases upon which such judgments are founded are always limited, and there may be exceptions beyond our observation.

The only kind of judgments that are the expression of true knowledge must, therefore, be synthetic judgments that are a priori. That is to say, they must express some new relation between ideas that is also universally and necessarily true. By a priori Kant means the universal and necessary; and, furthermore, he maintains that the universal and necessary, and nothing else, constitutes knowledge. He points out that we make such judgments. When we say that the three angles of a triangle equal two right angles, or that every event has acause, we are saying something universal and necessary, something not founded on experience. No one would admit that there were exceptions to these propositions. The question, then, that Kant tries to answer in his Critique of Pure Reason is, How are synthetic judgments a priori possible? Or since to Kant knowledge consists of synthetic judgments a priori, under what conditions is knowledge possible?[56]

For the sake of clearness, let us state this problem of Kant in another way. It is the nature of man to try by mere thinking to discover the nature of reality. The dogmatic school of Rationalists had attempted, without calling in experience to its aid, to weave out of pure thought answers to the questions about God, immortality, and nature. It had maintained that clear and distinct notions have a reality corresponding to them, and are therefore real. Judgments formed in this way are analytic a priori; but it is evident that while such analyses of thought have a cogency for thought, they do not necessarily have a corresponding reality. On the other hand, conclusions based on experience have a kind of validity for the real world, but they yield no certain truth about it. These are synthetic judgments a posteriori. If Hume is right in saying that these are the only judgments dealing with nature, then we have no certain truth about nature. They give generalizations that are useful on the whole, but their conclusions range only from possibility to high probability, and neverreach certainty. Besides (1) conceptual knowledge and (2) “knowledge of matters of fact,” Kant pointed out that there is a third kind. This is the only valid kind. This knowledge is based on synthetic judgments a priori. Such knowledge arises independently of experience, i. e. is a priori, and yet is valid for experience, i. e. is synthetic. Hume’s statement that such knowledge is synthetic a posteriori is not accepted by Kant. Kant is, therefore, bound to show how this third class of synthetic judgments a priori is possible, and how pure thought can be binding on experience.

The Proof of the Validity of Human Knowledge. If we turn now to review what we have said about Kant, we find that he undertakes to solve the problem, How can we know? by a critical study of the forms of the reason. We have found that the reason is essentially a synthetic power, and is the framework of the world of phenomena to which knowledge is limited. Knowledge is the complex thing, consisting of sensations as its woof and synthesis as its warp. To answer the question, Under what conditions is knowledge possible? we must study not sensations, but synthesis in its several forms. If Kant can show that the mind furnishes the a priori, that is, the universal and necessary forms to knowledge, he thinks he has proved his case. He has then explained why human knowledge is valid and thus proved that human knowledge is valid. Now Kant tries to show what the special a priori forms of knowledge are and in what the validity of such forms consists. In the first book of the Critique of Pure Reason, the Æsthetic, he undertakes to show what the a priori forms of mathematics are and how they make knowledge valid by being forms of mental synthesis. In the next part of theCritique, the Analytic, he tries to show what the a priori forms of the knowledge of physical science are and how they make physical science valid and objective. In the last part, the Dialectic, he discusses the a priori forms of the reason and shows why they have no validity in knowledge. These are three stages in which the knowing activity develops as three different forms of synthesis. The stages are perception, understanding, and reason. Each higher stage has the lower as its content. Finished knowledge involves perceptions, reproductions in the understanding, and a recognition of the whole by a thinking subject. Perception, understanding, and reason are not separate acts, but different levels of one consciousness. These will be taken up in succession.

1. In What does the Validity of Sense-Perception Consist? Kant points out: