Now here many objections present themselves, which fallaciously put forward charm not merely as a necessary ingredient of beauty, but as alone sufficient [to justify] a thing’s being called beautiful. A mere colour, _e.g._ the green of a grass plot, a mere tone (as distinguished from sound and noise) like that of a violin, are by most people described as beautiful in themselves; although both seem to have at their basis merely the matter of representations, viz. simply sensation, and therefore only deserve to be called pleasant. But we must at the same time remark that the sensations of colours and of tone have a right to be regarded as beautiful only in so far as they are _pure_. This is a determination which concerns their form, and is the only [element] of these representations which admits with certainty of universal communicability; for we cannot assume that the quality of sensations is the same in all subjects, and we can hardly say that the pleasantness of one colour or the tone of one musical instrument is judged preferable to that of another in the same[26] way by every one. If we assume with _Euler_ that colours are isochronous vibrations (_pulsus_) of the aether, as sounds are of the air in a state of disturbance, and,--what is most important,--that the mind not only perceives by sense the effect of these in exciting the organ, but also perceives by reflection the regular play of impressions (and thus the form of the combination of different representations) which I still do not doubt[27]--then colours and tone cannot be reckoned as mere sensations, but as the formal determination of the unity of a manifold of sensations, and thus as beauties in themselves. But “pure” in a simple mode of sensation means that its uniformity is troubled and interrupted by no foreign sensation, and it belongs merely to the form; because here we can abstract from the quality of that mode of sensation (abstract from the colours and tone, if any, which it represents). Hence all simple colours, so far as they are pure, are regarded as beautiful; composite colours have not this advantage, because, as they are not simple, we have no standard for judging whether they should be called pure or not.