 Williamson (2000b) defends Fitch’s reasoning against Kvanvig’s charge. He suggests that Kvanvig has no grounds for thinking that Fitch’s conjunction \(p \wedge \neg \exists x\exists t(Kxpt)\) does not designate rigidly. The reason Williamson gives is this. An expression is non-rigid if, when uttered in a fixed context, it varies its reference with the circumstances under which it is evaluated. But Kvanvig gives no convincing reason for thinking that Fitch’s conjunction, as uttered in a fixed context, varies its reference in this way. At best Kvanvig has shown that the conjunction varies its reference when uttered in varying contexts, since his argument is that a quantified sentence, when uttered at different worlds, will be about different objects. To think that this is sufficient for non-rigidity, Williamson complains, is to confuse non-rigidity for indexicality. Importantly, indexicality does not imply non-rigidity. For instance, ‘I am tired’ is about me, and continues to be about me when I evaluate its truth-value in counterfactual circumstances. The sentence might have been false. Had I gotten enough sleep, I would not be tired. Uttered in a fixed context, ‘I’ rigidly designates, even though it is an indexical. That is, even though, had it been uttered in a different context by somebody else, it would have been about somebody other than me. Analogously, even if quantified expressions are indexicals, it does not follow that they are non-rigid. And so, even if Fitch’s conjunction is an indexical expression, we have not been given a reason to think that it is non-rigid. If this is correct, then we have no grounds for thinking that Fitch has committed the modal fallacy in question.