the facts upon which that conception is based, that chance should have any place in the universe, or that events should follow anything but the natural order of cause and effect. We have come to look upon the present as the child of the past and as the parent of the future; and, as we have excluded chance from any share or part in the order of things, so in the present order of Nature men have come to neglect, even as a possibility, the notion of any interference with that order. And, whatever may be men's speculative notions upon those points, it is quite certain that every intelligent person guides his life and risks his fortune upon the belief that the order of Nature is constant, and the relation of cause to effect unchanged.
In fact, there is no belief which we entertain which has so complete a logical basis as that to which I have just referred. It tacitly underlies every process of reasoning; it is the foundation of every act of the will. It is based upon the broadest induction, and it is verified by the most constant, regular, and universal of deductive processes. But we must recollect that any human belief, however broad its basis, however defensible it may seem, is, after all, only a probable belief, and that our broadest generalizations are simply statements of the highest degrees of probability. Though we are quite clear about the constancy of Nature at the present time, and in the present order of things, it by no means follows necessarily that we are justified in expanding this generalization into the past, and in denying absolutely that there may have been a time when Nature did not follow a fixed order, when the relations of cause and effect were not definite, and when external agencies did not intervene in the general course of Nature. Cautious men will admit that such a change in the order of Nature may have been possible, just as a very candid thinker may admit that there may be a world in which two and two do not make four, and in which two straight lines do not inclose a space. In fact, this question with which I have to deal in the three lectures I shall have the honor of delivering before you, this question as to the past order of Nature, is essentially an historical question, and it is one that must be dealt with in the same way as any other historical problem.
I will, if you please, in the first place, state to you what are the views which have been entertained respecting the order of Nature in the past, and then I will consider what evidence is in our possession bearing upon these views, and by what light of criticism that evidence is to be interpreted. So far as I know, there are only three hypotheses which ever have been entertained, or which well can be entertained, respecting the past history of Nature.
Upon the first of these the assumption is, that the order of Nature which now obtains has always obtained; in other words, that the present course of Nature, the present order of things, has existed from all eternity. The second hypothesis is, that the present state of