Science, Renouvier claims, does not give us a knowledge of the absolute, but an understanding of the relative. It is in the light of his doctrine of relativity and of the application of the law of number that he criticises many of the attitudes adopted by the scientists. Whatever savours of the Absolute or the Infinite he opposes, and his view of cause depends on this. He scorns the fiction of an infinite regress, and affirms real beginnings to various classes of phenomena. Causality is not to be explained, he urges in his _Nouvelle Monadologie_, save by a harmony. He differs from Leibnitz, however, in claiming in the interests of freedom that this harmony is not pre-established. In meeting the doctrine of the reduction of the complex to the simple, Renouvier cites the case of “reducing” sound, heat, light and electricity to movement. This may be superficially correct as a generality, but Renouvier aptly points out that it overlooks the fact that, although they may all be abstractly characterised as movement, yet there are differences between them as movements which correspond to the differences of sensation they arouse in us. Renouvier upholds real differences, real beginnings, and, it must be added, a reality behind and beyond the appearances of nature. His _Monadologie_ admits that “we can continue to explain nature mathematically and mechanically, provided we recognise that it is an external appearance—that thought, mind or spirit is at the heart of it.” This links Renouvier to the group of new spiritualists. His attitude to science is akin to theirs. He does not fear science when it confines itself to its proper limits and recognises these. It has no quarrel with philosophy nor philosophy with it. Advance in science involves, he believes, an advance also in theology and in metaphysics.