The sciences which are in any peculiar sense modern take as an (unavowed) postulate the fact of consecutive change. Their inquiry always centers upon some manner of process. This notion of process about which the researches of modern science cluster, is a notion of a sequence, or complex, of consecutive change in which the _nexus_ of the sequence, that by virtue of which the change inquired into is consecutive, is the relation of cause and effect. The consecution, moreover, runs in terms of persistence of quantity or of force. In so far as the science is of a modern complexion, in so far as it is not of the nature of taxonomy simply, the inquiry converges upon a matter of process; and it comes to rest, provisionally, when it has disposed of its facts in terms of process. But modern scientific inquiry in any case comes to rest only provisionally; because its prime postulate is that of consecutive change, and consecutive change can, of course, not come to rest except provisionally. By its own nature the inquiry cannot reach a final term in any direction. So it is something of a homiletical commonplace to say that the outcome of any serious research can only be to make two questions grow where one question grew before. Such is necessarily the case because the postulate of the scientist is that things change consecutively. It is an unproven and unprovable postulate--that is to say, it is a metaphysical preconception--but it gives the outcome that every goal of research is necessarily a point of departure; every term is transitional.[2] A hundred years ago, or even fifty years ago, scientific men were not in the habit of looking at the matter in this way. At least it did not then seem a matter of course, lying in the nature of things, that scientific inquiry could not reach a final term in any direction. To-day it is a matter of course, and will be so avowed without argument. Stated in the broadest terms, this is the substantial outcome of that nineteenth-century movement in science with which the name of Darwin is associated as a catch-word. This use of Darwin's name does not imply that this epoch of science is mainly Darwin's work. What merit may belong to Darwin, specifically, in these premises, is a question which need not detain the argument. He may, by way of creative initiative, have had more or less to do with shaping the course of things scientific. Or, if you choose, his voice may even be taken as only one of the noises which the wheels of civilisation make when they go round. But by scientifically colloquial usage we have come to speak of pre-Darwinian and post-Darwinian science, and to appreciate that there is a significant difference in the point of view between the scientific era which preceded and that which followed the epoch to which his name belongs.