Further then, privation of every kind is something single and simply particular; but in substances there are several differences and efficacies. For silence is a thing but of one sort; but of sounds there are great variety, sometimes molesting, sometimes delightful to the sense. There are also the same differences in colors and figures, which vary as they occur to the senses. But that which is not to be felt, which is without color and void of quality, can never be distinguished, but is always like itself.