also, in regard to mind, the illusory idea that there are no degrees, no possible transition, between the extended and the unextended. But if these two postulates involve a common error, if there is a gradual passage from the idea to the image and from the image to the sensation; if, in the measure in which it evolves towards actuality, that is to say towards action, the mental state draws nearer to extension; if, finally, this extension once attained remains undivided and therefore is not out of harmony with the unity of the soul; we can understand that spirit can rest upon matter and consequently unite with it in the act of pure perception, yet nevertheless be radically distinct from it. It is distinct from matter in that it is, even then, memory, that is to say a synthesis of past and present with a view to the future, in that it contracts the moments of this matter in order to use them and to manifest itself by actions which are the final aim of its union with the body. We were right, then, when we said, at the beginning of this book, that the distinction between body and mind must be established in terms not of space but of time.
The mistake of ordinary dualism is that it starts from the spatial point of view: it puts on the one hand matter with its modifications in space, on the other unextended sensations in consciousness. Hence the impossibility of understanding how the spirit acts upon the body or the body upon spirit. Hence hypotheses which are
