Halliday & Matthiessen (1999: 72):
Categorisation has received much attention in recent work in linguistics, especially within the framework of cognitive science. The received tradition was the classical or Aristotelian conception of a category as a type definable in terms of necessary and sufficient conditions — its essential characteristics rather than its accidental ones. One central aim of cognitively oriented linguists has been to show that the Aristotelian conception does not apply to semantic categories, which have to be re-theorised in terms of prototype theory. The initial impetus came from a series of well-known experiments in categorisation by E. Rosch and by Labov (1973) and from Berlin & Kay's (1969) study of colour terms across languages; Wittgenstein's notion of family resemblances had provided an earlier insight within a philosophical frame of reference (cf. Ellis, 1993). Since there are now a number of summaries of these positions, and of the critique of the Aristotelian conception (e.g. Lakoff, 1987; Taylor, 1989), we will not review the discussion here.