Page:Popular Science Monthly Volume 15.djvu/499

Rh two straight lines, we perceive, without any mediate proof, that they can not inclose a space. Our commentator on Hume has equally misunderstood the nature of this necessity. He speaks of three kinds of necessity. The first is one merely requiring the consistent use of language: "The necessary truth A $$=$$ A means that the perception which is called A shall always be called A." This throws no light on our convictions. The second, "The necessary truth that 'two straight lines can not inclose a space,' means that we have no memory, and can form no expectation of their so doing." The instance he gives is a good example of an intuitive truth seen at once, and necessarily believed; but it surely implies vastly more than merely that we have no memory, and can form no expectation of two straight lines inclosing a space; it means that we perceive that, from the very nature of things, two such lines can not inclose a space. He has a third case of necessity, "The denial of the necessary truth that the thought now in my mind exists, involves the denial of consciousness." This is also an example of a self-evident, necessary truth, but it is so because we have an immediate knowledge of ourselves as existing.

6. Hume's doctrine of causation takes a double form; the one objective, the other subjective. These two are intimately connected, and yet they should be carefully separated. Hume held that objective causation is only invariable antecedence and consequence. This is a doctrine contradicted both by metaphysical and physical science. It seems very clear to me that our intuitions, looking on objects, declare that they have power. This is implied in the axiom that we know objects as having properties; and what are properties but powers? Then modern science has established the doctrine of the conservation of energy; namely, that the sum of energy, actual and potential, in the world is always one and the same. Causes are not causes simply because they are antecedents; they are antecedent of the effects because they have power to produce them.

It would be preposterous in so short a paper as this to dive into all the subtilties of the subjective question as to whether our belief in causation is intuitive, or is derived from a gathered experience. The settlement of this question will depend on the way we settle the one started under the last head, as to whether there are not truths which shine in their own light. If there be such truths, then causation is undoubtedly one of them. When we see a thing produced, a new thing, or a change in an old thing, we look for a producing cause having power in its very nature, and ready to produce the same effect in the same circumstances.

7. By his doctrine, defective as I reckon it, Hume undermined the argument for the Divine existence. There is evidence in his life, in his correspondence, and in his philosophic writings, that, like John Stuart Mill, in a later age, he looked with a feeling of favor upon the seeming evidence for the existence of a designing Mind in the