What we know is decided in the framework of the linguistic norms for knowledge ascriptions. Such include not just epistemic conditions but also communicative ones. Knowledge in communicative context is conditioned on public agreement upon the question and the nature of the presented evidence, sincerity of testimony and responsibility in claiming. This distinction is used here to explain the puzzles surrounding the problem of the criterion. The disparity between the epistemic principles and the communicative conditions of knowledge ascriptions is presented (...) here as a philosophically important question about the role of language in theoryconstruction. (shrink)