 Whether ‘tis possible for him, from his own imagination, to … raise up to himself the idea of that particular shade, tho’ it had never been convey’d to him by his senses? I believe there are few but will be of opinion that he can; and this may serve as a proof, that the simple ideas are not always deriv’d from the correspondent impressions; tho’ the instance is so particular and singular, that ‘tis scarce worth our observing, and does not merit that for it alone we shou’d alter our general maxim. (T 1.1.1.10/6)