motion the body in whole or in part.  When we make enquiries from the physiologist or the psychologist with regard to the origin of these images and representations, we are sometimes told that, as the centrifugal movements of the nervous system can evoke movement of the body, so the centripetal movements—­at least some of them—­give rise to the representation, mental picture, or perception of the external world.  Yet we must remember that the brain, the nerves, and the disturbance of the nerves are, after all, only images among others.  So it is absurd to state that one image, say the brain, begets the others, for “the brain is part of the material world, but the material world is not part of the brain.  Eliminate the image which bears the name ‘material world,’ and you destroy, at the same time, the brain and the cerebral disturbances which are parts of it.  Suppose, on the contrary, that these two images, the brain and the cerebral disturbance, vanish; ex hypothesi you efface only these, that is to say, very little—­an insignificant detail from an immense picture—­the picture in its totality, that is to say, the whole universe remains.  To make of the brain the condition on which the whole image depends is a contradiction in terms, since the brain is, by hypothesis, a part of this image."[Footnote:  Matter and Memory, p. 4 (Fr. pp. 3-4).] The data of perception are external images, then my body, and changes brought about by my body in the surrounding images.  The external images transmit movement to my body, it gives back movement to them.  My body or part of my body, i.e., my brain, could not beget a whole or part of my representation of the external world.  “You may say that my body is matter or that it is an image—­the word is of no importance.  If it is matter, it is a part of the material world, and the material world consequently exists around it and without it.  If it is an image—­that image can give but what has been put into it, and since it is, by hypothesis, the image of my body only, it would be absurd to expect to get from it that of the whole universe.  My body, an object destined to move other objects, is then a centre of action; it cannot give birth to a representation."[Footnote:  Matter and Memory, p. 5 (Fr. p. 4).] The body, however, is privileged, since it appears to choose within certain limits certain reactions from possible ones.  It exercises a real influence on other images, deciding which step to take among several which may be possible.  It judges which course is advantageous or dangerous to itself, by the nature of the images which reach it.  The objects which surround my body reflect its possible action upon them.  All our perception has reference, primarily, to action, not to speculation.[Footnote:  Cf.  Creative Evolution, p. 313 (Fr. p. 321).] The brain centres are concerned with motor reaction rather than with conscious perception, “the brain is an instrument of action and not of representation."[Footnote: