• sorites;
  • matching;
  • closeness;
  • comparison;
  • connectedness;
  • regular mediality;
  • regular minimality;
  • supervenience on stimuli;
  • tolerant responses;
  • vagueness


We develop a mathematical theory for comparative sorites, considered in terms of a system mapping pairs of stimuli into a binary response characteristic whose values supervene on stimulus pairs and are interpretable as the complementary relations ‘are the same’ and ‘are not the same’ (overall or in some respect). Comparative sorites is about hypothetical sequences of stimuli in which every two successive elements are mapped into the relation ‘are the same’, while the pair comprised of the first and the last elements of the sequence is mapped into ‘are not the same’. Although soritical sequences of this kind are logically possible, we argue that their existence is grounded in no empirical evidence and show that it is excluded by a certain psychophysical principle proposed for human comparative judgements in a context unrelated to soritical issues. We generalize this principle to encompass all conceivable situations for which comparative sorites can be formulated.