 Water produces an absurdity. If the privileged access thesis is true, s knows P9 non-empirically. If semantic externalism is true, s knows P10 a priori by mere conceptual analysis. Since P9 and P10 do entail Q9 and knowledge is presumably closed under known entailment, s knows Q9—which is an empirical proposition—by simply competently deducing it from P9 and P10 and without conducting any empirical investigation. As this is absurd, McKinsey concludes that the privileged access thesis or semantic externalism must be false.