It was this task which Lachelier set himself in his _Induction_. He had keenly felt the menace of science, as had Janet;[29] he had appreciated the challenge offered to it by Ravaisson’s ideas. Moreover, Lachelier’s acute mind discovered the crucial points upon which the new spiritualism could base its attack upon the purely scientific dogmatism. Whatever Leibnitz might have said, creative spontaneity of the spirit, as it was acclaimed by Ravaisson, could not easily be fitted into the mechanism and determinism upheld by the sciences. Ravaisson had admitted the action of efficient causes in so far as he admitted the action of mechanism, which is but the outcome of these causes. In this way he endeavoured to satisfy the essential demands of the scientific attitude to the universe. But recognising the inadequacy of this attitude he had upheld the reality of final causes and thus opposed to the scientists a metaphysical doctrine akin to the religious attitude of Hellenism and Christianity. [29] We refer here to the quotation from Janet’s _Problèmes du XIXe Siècle_, given above on p. 95. Janet himself wrote on _Final Causes_ but not Wlth the depth or penetration of Lachelier. Lachelier saw that the important point of Ravaisson’s doctrine lay in the problem of these two types of causality. His thesis is therefore devoted to the examination of efficient and final causes. This little work of Lachelier marks a highly important advance in the development of the spiritualist philosophy. He clarifies and re-affirms more precisely the position indicated by Ravaisson. Lacheher tears up the treaty of compromise which was drafted by Leibnitz to meet the rival demands of science with its efficient causes and philosophy with its final causes. The world of free creative spontaneity of the spirit cannot be regarded, Lachelier claims (and this is his vital point), as merely the complement of, or the reflex from, the world of mechanism and determinism.