A treatise of human nature: being an attempt to introduce the experimental method of reasoning into moral subjects. ... [pt.3]
Hume, David, 1711-1776.

A note to Vol. I. page 43. line 11. to the word (resemblance.)

'TIS evident, that even different simple ideas may have a similarity or resemblance to each other; nor is it necessary, that the point or circumstance of resemblance shou'd be distinct or separable from that in which they differ. Blue and green are different simple ideas, but are more resembling than blue and scarlet; tho' their perfect simpli∣city excludes all possibility of separation or Page  307 distinction. 'Tis the same case with parti∣cular sounds, and tastes and smells. These admit of infinite resemblances upon the ge∣neral appearance and comparison, without having any common circumstance the same. And of this we may be certain, even from the very abstract terms simple idea. They comprehend all simple ideas under them. These resemble each other in their simplicity. And yet from their very nature, which ex∣cludes all composition, this circumstance, in which they resemble, is not distinguishable nor separable from the rest. 'Tis the same case with all the degrees in any quality. They are all resembling, and yet the quality, in any individual, is not distinct from the degree.