The Philosophy of Immanuel Kant

by A. D. Lindsay

These difficulties were seen more clearly by Hume, at once the greatest and the most thorough-going of empiricists. He cut the knot in regard to mathematics by asserting that geometry, just because it has clearly an application to the existing world, had no more certainty than any other empirical inquiry, while arithmetic and algebra, he agreed, were certain, but confined their application to the sphere of our own ideas. Both positions are almost obviously inconsistent with the facts. In considering the nature of our judgments about concrete existences he raised a more profound problem. All such judgments, as he said, imply the principle of causation, or of what is called, in modern times, the principle of the uniformity of nature. That principle we take with us in our investigation of the existing world. Yet, as Hume saw, we do not observe causes; we only observe succession and change. We seem, therefore, to put into the world we see a necessity and uniformity which the observed facts do not warrant. How is this to be explained?

Hume's answer is ingenious. The principle of causation cannot be rationally justified, and the necessary connection we predicate of changes in the outside world is not in the things; it is only a feeling in ourselves, and is the result of custom. After seeing the same succession several times, we come somehow to feel differently about it, and that feeling of difference we express by saying that we have before us an instance not of simple succession, but of cause and effect.

This is not the place to discuss the difficulties of Hume's position; it is enough to notice how entirely passive it makes the mind, and how alien such an explanation is from the spirit of inquiry and discovery. If cause is simply the effect of custom on the mind, then the facts either produce that effect or they do not. In neither case is there anything to find out. But the scientist, in investigating causes, however strongly he may hold that he has to observe the facts, knows also that he has a problem to solve, that he has to discover the right way to go about it, must adopt some principle in dealing with the facts. Pure passivity will help him little.

Hume's account of causation, then, is really a denial of even empirical science, and yet it helped to make clear an important truth; for, although we do not get the principle of causation from experience, we have to go to experience to discover causal laws. We do not discover causation by analysing a cause and seeing that it is such that, from its nature, it must produce a certain effect. All knowledge of causation goes back to observed succession, though all cases of observed and even repeated succession are not cases of causation. Hume, therefore, was right in saying that where there could be no observed succession there could be no knowledge of causation.

Both the rationalistic and the empirical explanations of science had failed, the one because it could find no room for observation of facts, the other because it could find no room for principles governing that observation; and we shall see that Kant started with a consciousness of this double failure. He saw that Hume's criticism of causation raised problems for which the rationalist had no answer, and yet that the position reached by Hume was incompatible with the existence of science.

The same failure of both rationalism and empiricism had become evident in another sphere--that of morals and religion. The relation of philosophy to science is always twofold. Philosophy is partly concerned with analysing and reflecting on the methods of the different sciences, partly with seeking to adjust the rival and conflicting claims of the two great departments of man's life--science and religion.

It might seem, at first sight, as though in morals and religion rationalism were the only possible method to be approved by philosophy, for, inasmuch as morals are concerned with what ought to be, not with what is, they cannot depend on observation, but must be deduced from some principle above experience; nor are objects of religion, God and the soul, objects of observation. No man can "by searching find out God."

It was natural, therefore, that both on the Continent and in England morality and religion began by being rationalistic. Descartes believed that his mathematical method could be applied with success to demonstrate the truths of religion, while Locke includes morality along with mathematics among the a priori and certain sciences. But the history of eighteenth century controversy showed that, in spite of rationalist methods, neither morality nor religion could attain that certainty and general agreement which marked the mathematical sciences. Spinoza, applying the same method as Descartes, but with more consistency, arrived at a conception of God which most of his contemporaries regarded as "horrid atheism," and the general result of rational theology is well described by one of Kant's correspondents when he says that the more proofs of the existence of God he learnt, the more his doubts increased. In England the attempts made to found morality upon rationalist principles produced systems too barren to withstand the attack of empiricism fortified by the growing interest in history and anthropology. The Deist movement, an attempt to free religion from the incrustations of faith and deduce it from pure reason, showed that a religion founded on pure reason contained nothing worth believing. In Hume we have the final discrediting of reason in these spheres. He shows ingeniously that "the good Berkeley's" argument for the existence of God could be turned round to disprove the existence of the soul, and he concluded that religion was a sphere with which reason had no concern. In the sphere of morals the distinction between what ought to be and what is, the distinction on which rationalistic morals are based, had been discredited by a reduction of all conduct to Utilitarianism, a search for pleasure and a flight from pain mediated by sympathy. The consequences are described by Kant in his preface to the Critique of Pure Reason: "At present, after everything has been tried, so they say, and tried in vain, there reign in philosophy weariness and complete indifferentism, the mother of chaos and night in all sciences," though he hopefully continues, "but at the same time the source, or at least the prelude, of their near reform and of a new light, after an ill-applied study has rendered them dark, confused, and useless."

The earlier of the modern thinkers--Descartes among the rationalists, and Bacon among the empiricists--are full of hope. They have confidence in the human spirit. But increased reflection seemed only to bring distrust with it. The history of rationalism in theology showed that, in such matters, reason could prove absolutely opposing positions. Most men were ready to accept Hume's dictum that any one who follows his reason must be a fool and take refuge in an indifferentism which accepts whatever happens to be there.

The remedy for this state of affairs, Kant finds, is the critical method; for disbelief in reason is the reaction from overconfidence in it. Men had thought that reason could prove everything. Because these hopes had been frustrated, they now thought that it could prove nothing. Philosophy, he was convinced, would oscillate between overweening confidence and unwarranted distrust in itself until it had criticised human reason and discovered what it could do and what it could not. This is the task he set before himself. As the failure of eighteenth century philosophy, which had led to distrust of all philosophy, had been twofold--failure to give an intelligible explanation of the processes of scientific thought, and failure to find any standard by which to mediate between the conflicting claims of science and religion--the task of the critical philosophy is twofold. It attempts to explain and to justify the methods and assumptions of the sciences, and to find some solution of the conflict between theories of the world which seem to be based upon these methods and the assumptions and claims of morality and religion.