In this manner Fouillée endeavours to “rectify the scientific conception of evolution” by his doctrine of _idées-forces_. “There is,” he says,[34] “in every idea a commencement of action, and even of movement, which tends to persist and to increase like an _élan_. . . . Every idea is already a force.” Psychologically it is seen in the active, conative or appetitive aspect of consciousness. To think of a thing involves already, in some measure, a tendency toward it, to desire it. Physiologically considered, _idées-forces_ are found to operate, not mechanically, but by a vital solidarity which is much more than mere mechanism, and which unites the inner consciousness to the outer physical fact of movement. From a general philosophical point of view the doctrine of _idées-forces_ establishes the irreducibility of the mental, and the fact that, so far from the mental being a kind of phosphorescence produced as a result of the evolutionary process, it is a prime factor in that evolution, of which mechanism is only a symbol. Here Fouillée rises almost to the spiritualism of Ravaisson. Mechanism, he declares, is, after all, but a manner of representing to ourselves things in space and time. Scientists speak of forces, but the real forces are ideas, and other so-called “forces” are merely analogies which we have constructed, based upon the inner mental feeling of effort, tendency, desire and will.[35] [34] _La Liberté et le Déterminisme_, p. 97, 4e ed. [35] This was a point upon which Maine de Biran had insisted. (See p. 20.) The scientists have too often, as Fouillée well points in his work on _L’Evolutionnisme des Idées-forces_, regarded the concept of Evolution as all-sufficing, as self-explanatory. Philosophy, however, cannot accept such dogmatism from science, and asserts that evolution is itself a result and not in itself a cause. With such a view Fouillée is found ultimately in the line of the general development of the spiritual philosophy continuing the hostility to science as ultimate or all-sufficing. Further developments of this attitude are seen in Boutroux and in Bergson. In the work of Boutroux we find a continuation of that type of criticism of science which was a feature in Ravaisson and Lachelier. He has also affinities with Renouvier (and, we may add, with Comte), because of his insistence upon the discontinuity of the sciences; upon the element of “newness” found in each which prevents the higher being deduced from the lower, or the superior explained by reference to the inferior. Boutroux opposes Spencer’s doctrines and is a keen antagonist of Taine and his claim to deduce all from one formula. Such a notion as that of Taine is quite absurd, according to Boutroux, for there is no necessary bond between one and another science. This is Boutroux’s main point in _La Contingence des Lois de la Nature_.