That the world which we inhabit is a _Cosmos_, ruled by law and order, no one has ever attempted to deny. Only because laws are everywhere found awaiting discovery, is natural science a possibility. What such laws really are, we have already considered. They are, as Mr. Lewes puts it, the paths along which the forces of nature travel to their results; and it is only because these forces keep invariably each to its proper path, that we are able to follow them with our minds, either to learn anything concerning them, or to turn our knowledge to practical account. In something of the same manner, it is because we are assured that our railway trains will run on their appointed lines, that we can learn from Bradshaw how to get to Exeter or to Edinburgh;--but the forces of Nature are never derailed. It is, in fact, as we have heard, the first principle of Science, that "the reign of law is universal, the principle of continuity ubiquitous,"--and upon this the validity of all her methods and conclusions wholly depends. It is taken for granted, with absolute confidence, that what is once found to happen will be exactly repeated in like circumstances,--that the laws experimentally observed, regarding motion, heat, light, sound, chemical combination, electricity, magnetism, and the rest, will be faithfully obeyed, in every minutest particular, as certainly as suns will rise and set, or moons wax and wane. Were it not so, were the forces of Nature to act spasmodically and at random, and did not their common action so result as to establish or subserve other laws of bewildering complexity,--as in molecular dynamics, the mechanism of the heavens, and the processes of organic life,--we could learn no more from the study of nature than from a page of type which had been set up by an idiot, or an anthropoid ape. Here is another factor in our problem, and one which has from the first attracted the attention of thinking men. No feature of nature impressed them more than this same reign of law and order, apparent everywhere; and on this account they called the world _Cosmos_, instead of _Chaos_. And, since it is self-evident that everything must have a reason for its being, that whatever is not self-existent must have a cause other than itself, they felt compelled to enquire what manner of cause would account for law and order. The like enquiry we have still to pursue, and by methods radically the same as ever; for amid all her discoveries Science has found nothing which does anything whatever to furnish an answer. All that has been done is enormously to multiply the aspects under which the problem presents itself.