Not that it is our business to reject as false the notion of psychological intensity; but this notion demands interpretation, and the least that we can say against the attempt to turn it into a notion of size is that in doing so we are misunderstanding the specific character of the object studied. The same reproach must be levelled against association of ideas, the system of mechanical psychology of which the type is presented us by Taine and Stuart Mill. Already in chapters ii. and iii. of the "Essay", and again all through "Matter and Memory", the system is riddled with objections, each of which would be sufficient to show its radical flaw. All the aspects, all the phenomena of mental life come up for successive review. In respect of each of them we have an illustration of the insufficiency of the atomism which seeks to recompose the soul with fixed elements, by a massing of units exterior to one another, everywhere and always the same: this is a grammatical philosophy which believes reality to be composed of parts which admit of number just as language is made of words placed side by side; it is a materialist philosophy which improperly transfers the proceedings of the physical sciences to the sciences of the inner life. On the contrary, we must represent the state of consciousness to ourselves as variable according to the whole of which it forms a part. Here and there, although it always bears the same name, it is no longer the same thing. "The more the ego becomes itself again, the more also do its states of consciousness, instead of being in juxtaposition, penetrate one another, blend with one another, and tinge one another with the colouring of all the rest. Thus each of us has his manner of loving or hating, and this love or hate reflect our entire personality." ("Essay on the Immediate Data", pages 125-126.) At bottom Mr Bergson is bringing forward the necessity, in the case before us, of substituting a new notion of continuous qualitative heterogeneity for the old notion of numerical and spatial continuity. Above all, he is emphasising the still more imperious necessity of regarding each state as a phase in duration; and we are here touching on his principal and leading intuition, the intuition of real duration.