The distinction between vagueness and polysemy (which is crucial to traditional conceptions of lexical-semantic structure) is unstable: what appear to be distinct meanings from one point of view turn out to be instances of vagueness from another. The argumentation for this thesis is developed in three steps. First, three basic kinds of polysemy criteria are distinguished: a logical, a linguistic, and a definitional test. Second, it is shown that these three kinds of tests may yield mutually contradictory results. Third, it is argued that such inconsistencies also occur within each criterion, in the sense that there are contextual variations in the polysemy results that they yield. The consequences of this instability of the polysemy of an item are explored on three levels. First, on the pre-theoretical level, any reified conception of lexical meaning (as embodied in the conduit metaphor) has to be abandoned in favor of a flexible, procedural conception. Second, on the theoretical level, the view that the distinction between vagueness and polysemy may be used to distinguish between various kinds of prototypicality effects is undermined. And third, on the methodological level, the interpretative indeterminacy that accompanies the instability of polysemy raises the question of the objectivity of lexical semantics. (Dirk Geeraerts)