François Recanati Philosophie du langage et de l'esprit Collège de France Année 2023-2024 Colloque - Indexical Dynamics : Cognitive Dynamics as Mental Vehicle Identity: A Parity Argument from Polysemy Colloque organisé par François Recanati, Professeur du Collège de France, chaire Philosophie du langage et de l'esprit Intervenant(s) Michael Murez, Université de Nantes According to Fregean theories, thinking the same thought requires thinking not only about the same referent, but also thinking about it in the same way, under the same concept. Fregean theories face 'Schiffer's Puzzle' (Schiffer, 2005; Buchanan, 2016), i.e., some thoughts have what Schiffer calls "the relativity feature": "[their] entertainment requires different people, or the same person at different times, to think of [the same referent] in different ways" (Schiffer, 2005: 138). Paradigmatic examples are provided by 'cognitive dynamics' (Kaplan, 1989): A thinker thinks of some day as "today", a day passes, and the same thinker, keeping track of time, now thinks of the same day as "yesterday". The thinker is disposed to reason diachronically according to a pattern known as 'trading on coreference' (Campbell, 1988), which is often taken to indicate redeployment of the same concept. Yet it is tempting to say that the concepts expressed by "today" and "yesterday" are different, since they play different cognitive roles. According to Schiffer (2005: 149), "[i]t's clear the Fregean theory can't accommodate the relativity feature", because contra (e.g.,) Frege (1956 [1918]) and Evans (1981), there is no plausible account of what the concept which remains the same cross-contextually, and is expressed by different indexicals, is supposed to be. Against Schiffer and others, I defend a broadly Fregean position, which allows for diachronic identity between concepts, despite changes in (many aspects of) cognitive role and means of linguistic expression. I argue that such a position is independently motivated if, unlike traditional Fregeans, we identify concepts not with elements of content, but with 'robust' mental vehicles (Reference omitted for review). Concepts so construed are not individuated by the thinker's conception of their referent (the properties and relations they represent it as instantiating). My basic strategy for responding to Schiffer's puzzle is Fodorian in spirit (Fodor, 1990: 167): changes in a thinker's global inferential/behavioral dispositions across contexts trace back to aspects of their broader psychological state, which are not individuative of their concepts. They correspond to conceptional rather than conceptual change. This reply to Schiffer's Puzzle faces at least three objections: i) it seems to require conceptual atomism, which is unpopular; ii) it takes at face value the possibility of diachronic trading on coreference, which is controversial (e.g., Recanati, 2021); iii) it conflicts with the plausible principle that concepts themselves change along with modes of reference determination. In response, I will argue that i) my position is compatible with a plausible molecularist view of concepts; ii) diachronic trading on coreference based on enduring concepts, even granting it is unnecessary for assessments of rationality, is required for psychological explanation, and non-negotiable for vehicularists about concepts; iii) the empirical hypothesis that cognitive dynamics involves mere conceptional change is supported by a parity argument from cases which, I argue, analogously involve 'trading on coreference' despite change in modes of reference determination. The relevant cases, which to my knowledge have yet to be brought to bear on issues surrounding cognitive dynamics, involve regularly polysemous expressions, such as "bottle", which can mean a container or its contents. These expressions support cross-meaning anaphora, such as "Haddock gulped down the bottlei and tossed iti overboard" (Ortega-Andrés & Vicente, 2019; Qu