Rigid Designation and Semantic Structure

First, under the influence of the idea that, on pain of triviality, a general definition of rigidity should count natural kind terms in and the likes of ‘bachelor’ or ‘philosopher’ out, Soames (2002: Ch. 9) is tempted toward essentialism in characterizing the desired sense of ‘rigid’. (See pp. 251 ff., where Soames formulates the hypothesis that “a predicate is rigid if and only if it is an essentialist predicate” and investigates some more precise characterizations of what it means to be an essentialist predicate.) Soames does come to reject this line of thought, but nonetheless I think that his very temptation in this direction is illustrative of a widespread and potentially grave mistake. Kripke — along with Kaplan and Stalnaker (see note 20), among others — had to do much hard work to prove that rigidity is itself not a metaphysical thesis at all, let alone an objectionable one, before it and its ilk (i.e., the terms of quantified modal logic) were commonly acceptable philosophical parlance. The point that these terms are, as Kaplan (1986: 265) puts it, “prior to the acceptance (or rejection) of essentialism, not tantamount to it”, was crucial and hard won. To link rigidity with essentialism — indeed, with any particular metaphysical doctrine — risks losing some of this hard-won ground, risks adding currency to the mistaken objection that rigid designation is an obscure essentialist doctrine. Rigidity is a claim about the semantics of a designator, not about the essence of what is designated.