We have hitherto confined ourselves to feelings and efforts, complex states the intensity of which does not absolutely depend on an external cause. But sensations seem to us simple states: in what will their magnitude consist? The intensity of sensations varies with the external cause of which they are said to be the conscious equivalent: how shall we explain the presence of quantity in an effect which is inextensive, and in this case indivisible? To answer this question, we must first distinguish between the so-called affective and the representative sensations. There is no doubt that we pass gradually from the one to the other and that some affective element enters into the majority of our simple representations. But nothing prevents us from isolating this element and inquiring separately, in what does the intensity of an affective sensation, a pleasure or a pain, consist? [Sidenote: Affective sensations and organic disturbance.] Perhaps the difficulty of the latter problem is principally due to the fact that we are unwilling to see in the affective state anything but the conscious expression of an organic disturbance, the inward echo of an outward cause. We notice that a more intense sensation generally corresponds to a greater nervous disturbance; but inasmuch as these disturbances are unconscious as movements, since they come before consciousness in the guise of a sensation which has no resemblance at all to motion, we do not see how they could transmit to the sensation anything of their own magnitude. For there is nothing in common, we repeat, between superposable magnitudes such as, for example, vibration-amplitudes, and sensations which do not occupy space. If the more intense sensation seems to us to contain the less intense, if it assumes for us, like the physical impression itself, the form of a magnitude, the reason probably is that it retains something of the physical impression to which it corresponds. And it will retain nothing of it if it is merely the conscious translation of a movement of molecules; for, just because this movement is translated into the sensation of pleasure or pain, it remains unconscious as molecular movement. [Sidenote: Pleasure and pain as signs of the future reaction rather than psychic translations of the past stimulus.]