Indiscriminability and Phenomenal Continua

Abstract

The relation of perceptual indiscriminability is widely thought to be nontransitive: there can be a series of objects (stimuli) s 1 . . . s n in which s 1 is pairwise indiscriminable on some perceptual dimension from s 2 , and s 2 is indiscriminable from s 3 , and s 3 from s 4 , and so forth, but s n is discriminably different from s 1 . For example, Timothy Williamson writes that [t]wo stimuli whose difference is below the threshold cannot be discriminated. Since many indiscriminable differences can add up to a discriminable difference, one can have a series of stimuli each indiscriminable from its successor, of which the first member is discriminable from the last. Indiscriminability is a nontransitive relation. (Williamson 1994, 69)