qualities which succeed each other in our concrete perception and the homogeneous changes which science puts at the back of these perceptions in space? The first are discontinuous and cannot be deduced one from another; the second, on the contrary, lend themselves to calculation. But, in order that they may lend themselves to calculation, there is no need to make them into pure quantities: we might as well say that they are nothing at all. It is enough that their heterogeneity should be, so to speak, sufficiently diluted to become, from our point of view, practically negligible. Now, if every concrete perception, however short we suppose it, is already a synthesis, made by memory, of an infinity of 'pure perceptions' which succeed each other, must we not think that the heterogeneity of sensible qualities is due to their being contracted in our memory, and the relative homogeneity of objective changes to the slackness of their natural tension? And might not the interval between quantity and quality be lessened by considerations of tension, as the distance between the extended and the unextended is lessened by considerations of extension?
Before entering on this question, let us formulate the general principle of the method we would apply. We have already made use of it in an earlier work and even, by implication, in the present essay.
That which is commonly called a fact is not
