When we assume the principle of causality in the argument for the existence of God, what precisely is it that we assume? Only this: that whatever has begun to be, must have had an antecedent, or ground, or cause which accounts for it. We do not assume that every existence must have had a cause. We have no right, indeed, to assume that any existence has had a cause until we have found reason to regard it as not an eternal existence, but one which has had an origin. Whatever we believe, however, to have had an origin, we at once believe also to have had a cause. The theistic argument assumes that this belief is true. It assumes that every existence, once new, every event or occurrence or change, must have a cause. This is certainly no very large assumption: on the contrary, if any assumption can claim to be self-evident, it surely may. Thought implies the truth of it every moment. Sensation only gives rise to thought in virtue of it. Unless it were true there could be no such thing as thought. To deny that the principle of causality, understood as has been indicated, is true, would be to deny that reason is reason; it would be equivalent to affirming that to seek for a reason is always and essentially an unreasonable process. And, in fact, so understood, the principle never has been denied. Hume even did not venture to deny it, although he ought in consistency to have denied it, and obviously desired to be able to deny it. He did not, however, deny that every object which begins to exist must have a cause,--he did not venture to do more than deny that this is either intuitively or demonstratively certain, and that any bond or tie can be perceived between what is called a cause and what is called an effect. The inquiry which he instituted was not whether we pronounce it necessary that everything whose existence has a beginning should also have a cause or not, but for what reason we pronounce it necessary. He assumed that we pronounce it necessary, and his elaborate investigation into the nature of causation was undertaken expressly and entirely to discover why we do so. The conclusion to which he came--viz., that the causal judgment is an "offspring of experience engendered upon custom"--was not only a very inadequate and erroneous one in itself, but inconsistent with the reality of what it professed to explain: still the admission which has been mentioned was what was professed to be explained.