Historically this was Mr Bergson's starting-point and the origin of his thought: a criticism of time under the form in which common-sense imagines it, in which science employs it. He was the first to notice the fact that scientific time has no "duration." Our equations really express only static relations between simultaneous phenomena; even the differential quotients they may contain in reality mark nothing but present tendencies; no change would take place in our calculations if the time were given in advance, instantaneously fulfilled, like a linear whole of points in numerical order, with no more genuine duration than that contained in the numerical succession. Even in astronomy there is less anticipation than judgment of constancy and stability, the phenomena being almost strictly periodic, while the hazard of prediction bears only upon the minute divergence between the actual phenomenon and the exact period attributed to it. Notice under what figure common-sense imagines time: as an inert receptacle, a homogeneous milieu, neutral and indifferent; in fact, a kind of space. The scholar makes use of a like image; for he defines time by its measurement, and all measurement implies interpretation in space. For the scholar the hour is not an interval, but a coincidence, an instantaneous arrangement, and time is resolved into a dust of fixities, as in those pneumatic clocks in which the hand moves forward in jerks, marking nothing but a sequence of pauses. Such symbols are sufficient, at least for a first approximation, when it is only a question of matter, the mechanism of which, strictly considered, contains nothing "durable." But in biology and psychology quite different characteristics become essential; age and memory, heterogeneity of musical phases, irreversible rhythm "which cannot be lengthened or shortened at will." ("Creative Evolution", page 10.) Then it is that the return of time becomes necessary to duration. How are we to describe this duration? It is a melodious evolution of moments, each of which contains the resonance of those preceding and announces the one which is going to follow; it is a process of enriching which never ceases, and a perpetual appearance of novelty; it is an indivisible, qualitative, and organic becoming, foreign to space, refractory to number. Summon the image of a stream of consciousness passing through the continuity of the spectrum, and becoming tinged successively with each of its shades. Or rather imagine a symphony having feeling of itself, and creating itself; that is how we should conceive duration.