[Bain's footnote 18: Discrimination and Retentiveness (the having of Ideas as the produce of Sensations) are different functions, although mutually involved, and, in all likelihood, developed in proportionate degrees in the same organ. We begin by discriminating changes of impression; this process is necessary in order to our having even a sensation; the more delicate the discriminating power, the greater the number of our primary sensations. He that can discriminate twenty shades of yellow has twenty sensations of yellow; the two statements express the same fact. These various sensations being often repeated, acquire at last an ideal persistence; they can be maintained as ideas, without the originals. The function or power of the Intellect whereby they are thus rendered self-subsisting as ideas, is not the same function as discrimination; we call it Memory, Retentiveness, Adhesiveness, Association, and so on. What may be affirmed about it, on the evidence of induction, is, that where discrimination is good, memory or retentiveness is also good. The discriminative eye for colour is accompanied with a good memory for colour; the musical ear is both discriminative and retentive.--_B._] 5. Since we distinguish smells, as well as tastes, {57} we have the same proof of the number and distinctness of the ideas of this class of sensations. There is none of the numerous smells to which we have been accustomed, which we do not immediately recognise. But for that recognition the idea of the past sensation must be conjoined with the present sensation. 6. Of that class of sensations, which I have called sensations of disorganization, we have also ideas. We are capable of having the thought of them when the sensation is gone; and that thought is the idea. A spark from the candle flew upon my hand: I had the sensation of burning. I at this moment think of that sensation; that is, I have the idea of that sensation; and I can think of it, as different from ten thousand other painful sensations: that is, I have ideas of as many other sensations of this class.