The superstitions and credulities of the Middle Ages eventuated, during the course of the eighteenth century, in the Encyclopædism of French philosophy. The grounds upon which the Church based her doctrine of the supernatural were fiercely attacked. The proofs brought forward to prove the insufficiency of such grounds were assumed to prove more than lack of logic in the Church; they were taken as proofs, that, in the nature of things, there is no evidence for the supernatural, in any sense of the term; in other words, that there is no knowledge within the reach of mortals, except that which relates to the physical,--to this earth, as the only phase of existence,--to the vital body, as the all of the human being. Emotional and intellectual phenomena were but results of material organization, as heat is the result of combustion: they exhibited themselves so long as vitality continued; they disappeared when death supervened, as the warmth from a fire dies out with the cessation of combustion. No hypothetical soul was needed to account for the thousand phenomena of thought or of sensation. Pneumatology was no science, but the mere fancy of an excited imagination. Not to the literature and the social life of France alone was this materialistic influence confined. The mind of Germany, of England, and, more or less, of the rest of Europe, and of America, was pervaded by it. The tendency, all over the civilized world, was towards unbelief, not merely in miracles, but in all things spiritual. Science, with her strict tests and her severe inductions, lent her aid in the same direction. It does not seem to have occurred to the philosophers of the Encyclopædian school that a doctrine is not necessarily false because an insufficient argument is brought forward to prove it. It does not appear to have occurred to skeptical physicists that there may be laws of Nature regulating ultramundane phenomena, as fixed, as invariable, as those which decide the succession of geological phenomena and the products of chemical combinations. Here is a theory which is worth considering. May it not be that God adapts the proofs of that which it is important that man should know to the intellectual progress of mankind? Is it certain that the same evidence which sufficed for the foundation of religious faith five hundred years ago will suffice equally well to-day? Truths are eternal; laws of Nature vary not. But of the world's thoughts there is a childhood, a youth, a manhood; and there may be various classes of arguments suited to various stages of progress.