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

by Herbert Ernest Cushman

Hume evidently follows Berkeley in his criticism of material substance. But Berkeley went only halfway. Berkeley had found that bodies were only conjunctions of sensations, and he had rejected as meaningless the unknown substance behind them. He did not see that the same attack could be made upon spiritual substances. Berkeley’s argument against the substance of the cherry could be used against the Ego or the Soul. Have I the impression of my Ego? Can I touch it or see it? The simple test shows that I know nothing about it, and I cannot affirm whether or not it exists. But if the conception of the Soul has no reality as an object of knowledge, how can it be psychologically explained? How does it arise in the mind? The idea of the Soul is due to the frequent reappearance of the same trains of thought in my mind. Their similarity gives rise to the feeling that a metaphysical identity, or Soul, exists behind them.

The Association of Causation: Hume’s Attack on Science. Among the many traditional conceptions upon which Hume turned his critical examination, that of causation occupies the most of his attention. He discussesit both in the Treatise and in the Enquiry. He is the first philosopher since Aristotle to give it comprehensive treatment. He saw that all philosophical, theological, and indeed scientific knowledge rests upon this conception of causation. It was accepted without question by the Scholastics of the Middle Ages, the Rationalists of the Renaissance, and the scientists of his own time. If the conception is valid, Hume’s criticism goes for naught; for “by means of that relation we can go beyond the evidence of our memory and senses.” In that case what becomes of Hume’s psychological analysis that all knowledge consists of impressions and ideas? And if Hume’s psychology falls, all his criticism of the spiritual and the material substance falls also. Upon the validity of the concept of cause depend many of the scholastic arguments for the existence of God, whose existence we can demonstrate although He is not an object of sense impression. Imagination can then go on unrestricted; for God is accepted not only as cause, but as first or uncaused cause. Descartes, Leibnitz, and even Berkeley and Locke had accepted the causal argument for the existence of God, although the latter two had pretended to restrict knowledge to sense-perceptions and ideas. Again, the causal concept has been the foundation for the belief in a functioning soul behind the mental and physical activities of a human being; and on the same causal concept man has argued from sensations to their material substrate. All this is unwarranted and unrestricted knowledge because it “goes beyond the memory and senses.” Not only theology, but science itself has gone “beyond the memory and senses.” Hume dares to doubt the certainty of the causal principle even in scientific knowledge. Is thereany necessary connection among events so that with certainty we can predict the occurrence of one event if another is given? Is there in nature and history any causal law so binding that every event is a necessary result of what has gone before and a necessary cause of what will come? The question of cause is, therefore, paramount with Hume. If he is successful in impeaching cause as he has been in the case of substance, scientific theory must fall with theological dogma.

In his review of the conceptions of time and space (association by contiguity), Hume had found succession to be a quality of impressions and to be given with them. But that is all that can be said—the relation is one of time order, but not a relation that is necessary. The outer impressions happen to occur thus and thus; they need not have occurred thus, and may never occur in this order again. This temporal order is not by any means a causal order. The idea of cause is that of power transferred, but we have no impression of power. Impressions come as sequences, not as consequences or as powers. Sequences of impressions are the only “matters of fact”; consequences are not “matters of fact.” They must, therefore, be only “relations between ideas” and have no objective reality. From Hume’s point of view this is sufficient to show that cause is not valid and real.

To deny that we have the concept of cause would, however, be nonsense. We do have the concept, and how is its psychological origin to be explained? How does the idea arise? It does not originate (1) as an a priori concept, i. e. by an analysis of ideas, nor (2) as an outer impression, i. e. a sensation, nor (3) as memory, since memories are images of impressions. Theidea of cause originates from an inner impression—a strong and lively feeling connected with the imagination. But how does it happen that the feeling is so strong that it makes us believe the idea, with which it is connected, is a reality? The feeling does not arise from a single instance of conjunction of two impressions, but from the conjunction of two ideas repeated many times. The belief in cause is a feeling originating in the constant conjunction of impressions. This explains why the ideas that fire will burn, that poison will kill, that water will wet—are so lively. The conjunction occurs many times, and an inner necessity or compulsion arises to imagine the second impression after the first. Given the first idea, we learn to expect the second. Repetition produces nothing new in objects, but it produces in the mind a new feeling to pass from one idea to the idea usually attending it. Necessity exists in the mind and not in the objects.

The Extent and Limits of Human Knowledge. What remnants of knowledge remain after Hume has applied his destructive criticism? His critics would answer that, if Hume had been consistent, no knowledge whatever would remain. Upon the basis of pure positivism, that all knowledge is composed of impressions and their copies, knowledge is an impossibility. But he introduced an additional element, “relations,” that made knowledge possible because it afforded synthesis and allowed distinctions.

Taking Hume’s doctrine as it stands, his results are these. There are two classes of sciences, the formal and the empirical. The formal includes logic and mathematics, and consists of knowledge of relations between ideas. Such knowledge has certainty and validity. Empiricalsciences consist in knowledge of matters of fact. Such knowledge never amounts to more than probability. There is no certainty or demonstration in natural science. Its results call forth not conviction, but belief. Beyond these subjects we have no knowledge whatever. Metaphysics and theology are only fictions. Beyond impressions and the copies of impressions we can make no assertions. The tendency of thought to trench beyond its own territory is the cause of all our metaphysical difficulties. It tries to do what it was not intended to do, and the result is abstract ideas. Reason and the relation of resemblance give us the erroneous idea of spiritual and material substance; imagination and the relation of cause give the erroneous idea of the fundamental principle of nature.

Hume’s Theory of Religion and Ethics. Hume is so true an empiricist to the end that he is a remarkable exception among the philosophers of the Enlightenment. He alone among philosophers shows the historical sense in the application of his positivism to religion and morals. In general the Enlightenment took no account of the past; in this Hume differs from his contemporaries.

Hume was the destroyer of deism because he advanced historical evidence against deism. Deism had three principles: that religion is the object of scientific investigation; that religion had its origin in the reason; and that “natural religion” is the oldest form. Hume agreed to the first proposition, but he revealed his historical instinct by showing that religion did not originate in the reason, but in the feelings; and that not “natural religion,” but idolatry, etc., is the oldest form. Furthermore, he stood almost alone among philosophers of the period in building ethics upon the feelings rather thanupon the intellect. The ethical motives of man are pleasure and pain, and not an idea of the reason. Hume’s historic sense led him to this conclusion.

Both morals and religion should be empirically investigated. As in science, so in them the most cogent conclusions are only probable and not intuitive. Our moral activities are under the same kind of law of cause that exists in the world of nature-phenomena. The will is determined by the feelings, and the reason is the slave of the passions. Our moral judgment is based on the feeling of sympathy (Adam Smith). It is practically probable that there is a purpose in the world and therefore a God. But this cannot be established. On the same principle of probability the world may have grown up mechanically or by chance. Religion is naturally reasonable enough, but its doctrines cannot be proved.

The Scottish School. This school represents in Great Britain the reaction from the sensualism of the Enlightenment. The Scottish School was the British reply to Hume, just as Kant was the German reply. They were the late eighteenth century reactions in two countries to the Enlightenment. The teaching of Kant was, however, also the beginning of a new movement and a new period. The Scottish School has no such importance.