[392] It is chiefly in _Matter and Memory_ (in which, by the way, there are pages and pages of criticism of the rationalism of philosophy that are as valuable as anything we have in philosophy since the time of Descartes--Kant not excepted) that we are to look for the detailed philosophy of sensation and of perception, and the detailed philosophy of science upon which this protest of Bergson’s against the excesses of “conceptualism” rests. I indicate, too, at different places in this chapter some of the other special considerations upon which it rests. The gist of the whole is to be found, perhaps, in his contention that our science and our philosophy of the past centuries have both regarded “perception” as teaching us (somehow) what things _are_ independently of their effect upon us, and of their place in the moving equilibrium of things--the truth being on the contrary (with Pragmatism and Humanism) that our knowledge has throughout a necessary relation to ourselves and to our place in the universe, and to our liberation from matter in the life of the spirit. [393] He expresses this idea in the following way in the Introduction to _Matter and Memory_: “Psychology has for its object the study of the human mind for practical utility,” whereas in “metaphysics” we see “this same mind striving (the idea, as we say elsewhere, is not free from difficulty) to transcend the conditions of useful action and to come back to itself _as to a pure creative energy_.” Or in the following sentences from his _Creative Evolution_: “We must remember that philosophy, as we define it, _has not yet become completely conscious of itself_. Physics understands its role when it pushes matter into the direction of spatiality; but has metaphysics understood its role when it has simply trodden the steps of physics, in the chimerical hope of going farther in the same direction? _Should not its own task be, on the contrary, to remount the incline that physics descends, to bring matters back to its origins, and to build up progressively a cosmology which would be, so to speak, a reversed psychology._ All that which seems _positive_ to the physicist and to the geometrician would become, from this new point of view, an interruption or inversion of the true positivity which _would have to be defined in psychological terms_” (pp. 219–20, italics mine).