PHILOSOPHICAL COROLLARIES.--These strictly scientific theories associated with the name of Laplace, Lavoisier, and Dalton tended to strengthen in the popular estimation, the philosophical conclusions of writers like Holbach. The scientists themselves remained "agnostic" with regard to questions that lay outside their scope: they maintained here the correct attitude for scientific research. The question put by Napoleon to Laplace, why he had not introduced the name of God into the _Mechanique Celeste_, was out of place, and deserved the crushing reply it received. Scientific research is not concerned with questions of philosophy. Still, it did not escape popular attention that the old pillar of a mechanistic view of the universe now seemed to be reinforced by another. The theory of _the conservation of energy_ was now supplemented by that of the _indestructibility of matter_ (Lavoisier). And to crown all, the old atomic theory, which Lucretius had made the foundation of his dogmatic materialism, was now re-established on an experimental basis. So far as physical science was concerned, the situation seemed menacing to a religious view of life. Men felt that they inhabited a world of indestructible matter, moved by a certain measure of force, unchangeable and fixed. The prison of determinism and matter was closing around them. CHAPTER VI RISE OF GERMAN IDEALISM AN UNSTEMMED TIDE.--In spite of those important reactions of thought which we have associated with the name of Spinoza, Leibniz, and Pascal, the mechanical view had not ceased, as the last chapter has shown us, to extend itself during the eighteenth century, when it became highly fashionable in progressive circles. COMMON-SENSE PHILOSOPHY.--The strength of this mechanical view lies in the fact that it stands on the shoulders of a natural science which itself has its feet firmly planted on the irrefragible rock of sense-experience. The mechanical view thus rests, in the last resort, upon the belief (which is held everywhere with confidence by plain men) that sense-experience is a sound foundation for knowledge. The importance of this belief had been recognised by the English philosopher, Locke (1632-1704), who in his _Essay concerning Human Understanding_ (1690), lays it down that all human knowledge is based, ultimately, upon sense-experience. This highly important work had an immense influence, and, under Locke's tutelage, many thinkers regarded with suspicion any knowledge which might seem not to be derivable, in one way or another, from that source.