What is a secondary cause? or, in other words, what is a law of nature considered as a cause? It is simply a uniform mode of operation. We find that heavy bodies uniformly tend towards the earth's centre, and that we call the law of gravity; but if those bodies sometimes ascended, and sometimes moved horizontally, under the same circumstances, we could not infer the existence of such a law. Now, there must be some cause for uniformity of operation in nature. There must be some foreign power, which gives the uniformity, since it is certain that the law itself can possess no efficiency. We may, indeed, find one law dependent upon a second law, and this upon a third, and so on. But the inquiry still arises, What gives the efficiency to this second and third law? and still the answer must be, Something out of itself. So that if we run back on the chain of causes ever so far, we must still resort to the power of the Deity to find any efficiency that will produce the final result. In most cases, we can trace back only one or two links on the chain. For instance, we account for the falling of all bodies by the law of gravity. But philosophers have wearied themselves in vain to find any cause for gravity, except in the will of God. The failure of every other hypothesis, though invented by such men as Newton and Le Sage, has been signal. Sound philosophy, then, requires us to infer that gravity owes its efficiency to the direct exertion of divine power. And so in all cases, when we can no longer discover second causes for any phenomenon, why should we imagine their existence, rather than refer it to the agency of God? For go back as far as we may, and discover a thousand intervening causes, the efficiency resides alone in God. We have no evidence that even infinite power can communicate that efficiency to the laws of nature, so that they can act without the presence and agency of God. The common idea, which endows those laws with independent power, will not bear examination. In the second place, if natural operations do not depend upon the exercise of divine power, no other efficient cause can be assigned for their production.