Now, between this succession without externality and this externality without succession a kind of endosmotic commerce goes on. Although the successive phases of our conscious life interpenetrate, some of them correspond to simultaneous oscillations of the pendulum; and since each oscillation is distinct--that is, one is no more when another is produced--we come to make the same distinctness between the successive moments of our conscious life. The oscillations of the pendulum decompose it, as it were, into mutually external parts: hence the erroneous idea of an internal homogeneous duration analogous to space, whose identical moments follow each other without interpenetrating. On the other hand, the pendular oscillations benefit by the influence they have exerted on our conscious life. Thanks to the recollection of their collective whole, which our consciousness has organized, they are preserved and then aligned; in short, we create a fourth dimension of space for them, which we call homogeneous time, and which enables the pendular movement, although produced in a certain spot, to be juxtaposited with itself indefinitely. There is a real space, without duration, but in which phenomena appear and disappear simultaneously with our states of consciousness. There is a real duration, whose heterogeneous moments interpenetrate, but each of which can touch a state of the external world contemporaneous with it, and so be made separate from other movements. From the comparison of these two realities arises a symbolic representation of duration drawn from space. The trait common to these two terms, space and duration, is simultaneity, the intersection of time and space. This is how duration comes to get the illusory appearance of a homogeneous medium. But time is not measurable. Neither is motion, the living symbol of time. Like duration, motion is heterogeneous and indivisible. But it is universally confused with the space through which the movable passes. The successive positions of the movable are in space, but the motion is not in space. Motion is passing from one position to another, which operation occupies duration and has reality only for a conscious spectator. Things occupy space; processes occupy duration, because they are mental syntheses and are unextended.