John MacFarlane

In lieu of an abstract, here is a brief excerpt of the content:Journal of the History of Philosophy 39.3 (2001) 454-456 [Access article in PDF] Michael Potter. Reason's Nearest Kin: Philosophies of Arithmetic from Kant to Carnap.New York: Oxford University Press, 2000. Pp. x + 305. Cloth, $45.00. This book tells the story of a remarkable series of answers to two related questions:(1) How can arithmetic be necessary and knowable a priori? [End Page 454](2) What accounts for the applicability of arithmetic to matters of empirical fact?These are philosophical questions, part of a "wider puzzle of explaining the link between experience, language, thought, and the world" (18). But answers to them are heavily constrained by technical results in logic and mathematics, and most of Potter's protagonists are either mathematicians (Frege, Dedekind, Ramsey, Hilbert, Gödel) or mathematically trained philosophers (Kant, Russell, Carnap). (Only Wittgenstein fits neither category.) Potter, whose doctorate was in pure mathematics, is an able guide.It is not hard to think of answers to these questions taken singly; what is hard is answering both at the same time. Formalists can easily explain why arithmetic does not depend for its justification on empirical fact—it is just a game with symbols, not responsible to anything beyond its own rules—but they then have trouble explaining why the world of empirical fact is constrained by this game. Empiricists can explain the applicability of arithmetic in just the same way they explain the applicability of physics, but they then must then explain away the apparent a prioricity and necessity of arithmetic. Kant was the first to propose a plausible answer to both questions: arithmetic is both necessary and empirically applicable because it is grounded in the spatio-temporal form of any possible experience.What unites Frege, Dedekind, Russell, Ramsey, Hilbert, and Carnap is that they reject Kant's answer while continuing to seek an answer to his question: how can arithmetic's necessity be reconciled with its applicability? Potter helpfully classifies their projects by the surrogates they substitute for Kant's appeal to the form of spatio-temporal intuition: Frege and Dedekind appeal to thought, Russell to necessary features of the world, Wittgenstein, Ramsey, and Carnap to language, and Hilbert to the necessary structure of our experience of finitary combinations of objects. (Revealingly, the logicists are not grouped together in Potter's taxonomy.) A chapter (or two) is devoted to each of these thinkers, plus Kant and Gödel.This breadth of coverage does not come at the price of superficiality: Potter's chapters are (by and large) accurate, penetrating, and full of interesting insights. I cannot think of another book that offers such clear explanations of the many mathematical concepts and distinctions one must grasp in order to follow debates in the philosophy of arithmetic. The Russell chapters are enhanced by numerous quotations from archival material. The exposition of Hilbert's programme and the implications for it of Gödel's theorems is the best I have seen. The discussions of Wittgenstein's views on arithmetic and of Carnap's syntactical approach also shine. The chapters on Kant and Frege are somewhat weaker; the discussion of Kant, in particular, would have benefited from some engagement with Michael Friedman's views.But the real contribution of Potter's book is its integration of these nine thinkers into a single coherent story. No one will be surprised that Russell's motivations can only be understood in light of Frege's failures, or that many features of Wittgenstein's cryptic work become clearer when seen in light of the specific problems with Russell's system. But there are also some less obvious payoffs: for example, Hilbert's programme is usefully compared with Russell's regressive method (227-8), and Carnap and Russell are shown to face a common dilemma (269, 286).If there is a central theme to Potter's story, it is "how often we have had to reject an [End Page 455] account not for philosophical reasons but for technical ones" (278). Frege's program founders on Russell's paradox, Russell's...

To assert something is to perform a certain kind of act. This act is different in kind both from other speech acts, like questions, requests, commands, promises, and apologies, and from acts that are not speech acts, like toast buttering and inarticulate yodeling. My question, then is this: what features of an act qualify it as an assertion, and not one of these other kinds of act? To focus on a particular example: in uttering “Bill will close the window,” one might be practicing English pronunciation, asserting that Bill will close the window, or requesting that Bill close the window. What makes it the case that one is doing one of these and not another?

In lieu of an abstract, here is a brief excerpt of the content:Journal of the History of Philosophy 39.3 (2001) 454-456 [Access article in PDF] Michael Potter. Reason's Nearest Kin: Philosophies of Arithmetic from Kant to Carnap.New York: Oxford University Press, 2000. Pp. x + 305. Cloth, $45.00. This book tells the story of a remarkable series of answers to two related questions:(1) How can arithmetic be necessary and knowable a priori? [End Page 454](2) What accounts for the applicability of arithmetic to matters of empirical fact?These are philosophical questions, part of a "wider puzzle of explaining the link between experience, language, thought, and the world" (18). But answers to them are heavily constrained by technical results in logic and mathematics, and most of Potter's protagonists are either mathematicians (Frege, Dedekind, Ramsey, Hilbert, Gödel) or mathematically trained philosophers (Kant, Russell, Carnap). (Only Wittgenstein fits neither category.) Potter, whose doctorate was in pure mathematics, is an able guide.It is not hard to think of answers to these questions taken singly; what is hard is answering both at the same time. Formalists can easily explain why arithmetic does not depend for its justification on empirical fact—it is just a game with symbols, not responsible to anything beyond its own rules—but they then have trouble explaining why the world of empirical fact is constrained by this game. Empiricists can explain the applicability of arithmetic in just the same way they explain the applicability of physics, but they then must then explain away the apparent a prioricity and necessity of arithmetic. Kant was the first to propose a plausible answer to both questions: arithmetic is both necessary and empirically applicable because it is grounded in the spatio-temporal form of any possible experience.What unites Frege, Dedekind, Russell, Ramsey, Hilbert, and Carnap is that they reject Kant's answer while continuing to seek an answer to his question: how can arithmetic's necessity be reconciled with its applicability? Potter helpfully classifies their projects by the surrogates they substitute for Kant's appeal to the form of spatio-temporal intuition: Frege and Dedekind appeal to thought, Russell to necessary features of the world, Wittgenstein, Ramsey, and Carnap to language, and Hilbert to the necessary structure of our experience of finitary combinations of objects. (Revealingly, the logicists are not grouped together in Potter's taxonomy.) A chapter (or two) is devoted to each of these thinkers, plus Kant and Gödel.This breadth of coverage does not come at the price of superficiality: Potter's chapters are (by and large) accurate, penetrating, and full of interesting insights. I cannot think of another book that offers such clear explanations of the many mathematical concepts and distinctions one must grasp in order to follow debates in the philosophy of arithmetic. The Russell chapters are enhanced by numerous quotations from archival material. The exposition of Hilbert's programme and the implications for it of Gödel's theorems is the best I have seen. The discussions of Wittgenstein's views on arithmetic and of Carnap's syntactical approach also shine. The chapters on Kant and Frege are somewhat weaker; the discussion of Kant, in particular, would have benefited from some engagement with Michael Friedman's views.But the real contribution of Potter's book is its integration of these nine thinkers into a single coherent story. No one will be surprised that Russell's motivations can only be understood in light of Frege's failures, or that many features of Wittgenstein's cryptic work become clearer when seen in light of the specific problems with Russell's system. But there are also some less obvious payoffs: for example, Hilbert's programme is usefully compared with Russell's regressive method (227-8), and Carnap and Russell are shown to face a common dilemma (269, 286).If there is a central theme to Potter's story, it is "how often we have had to reject an [End Page 455] account not for philosophical reasons but for technical ones" (278). Frege's program founders on Russell's paradox, Russell's...

We consider a paradox involving indicative conditionals (‘ifs’) and deontic modals (‘oughts’). After considering and rejecting several standard options for resolv- ing the paradox—including rejecting various premises, positing an ambiguity or hidden contextual sensitivity, and positing a non-obvious logical form—we offer a semantics for deontic modals and indicative conditionals that resolves the paradox by making modus ponens invalid. We argue that this is a result to be welcomed on independent grounds, and we show that rejecting the general validity of modus ponens is compatible with vindicating most ordinary uses of modus ponens in reasoning.

According to Semantic Minimalism, every use of "Chiara is tall" (fixing the girl and the time) semantically expresses the same proposition, the proposition that Chiara is (just plain) tall. Given standard assumptions, this proposition ought to have an intension (a function from possible worlds to truth values). However, speakers tend to reject questions that presuppose that it does. I suggest that semantic minimalists might address this problem by adopting a form of "nonindexical contextualism," according to which the proposition invariantly expressed by "Chiara is tall" does not have a context-invariant intension. Nonindexical contextualism provides an elegant explanation of what is wrong with "context-shifting arguments" and can be seen as a synthesis of the (partial) insights of semantic minimalists and radical contextualists.

According to “sensitive invariantism,” the word “know” expresses the same relation in every context of use, but what it takes to stand in this relation to a proposition can vary with the subject’s circumstances. Sensitive invariantism looks like an attractive reconciliation of invariantism and contextualism. However, it is incompatible with a widely-held view about the way knowledge is transmitted through testimony. If both views were true, someone whose evidence for p fell short of what was required for knowledge in her circumstances could come to know that p simply by feeding her evidence to someone in less demanding circumstances and then accepting his testimony.

This is a lightly edited version of my comments on Brandom’s Lecture 2, as delivered in Prague at the “Prague Locke Lectures” in April, 2007. I try to say why Brandom’s proposed demarcation is significant, by placing it in a broader context of demarcation proposals from Kant to the twentieth century. I then raise some questions about the basic ingredients of Brandom’s demarcation—the notions of PP-sufficiency and VP-sufficiency—and question whether the vocabulary of conditionals, Brandom’s paradigm for logical vocabulary, can be universal-LX.

In Confusion: A Study in the Theory of Knowledge, Joseph Camp argues that the reasoning of a person who has confused two objects in her thought and talk ought to be appraised using a four-valued relevance logic. I discuss two key moves in Camp’s argument: the assumption that charity to the reasoner requires recognition of her arguments as valid, and the argument that validity for a truth-valueless discourse should not be defined in terms of truth preservation. I then question whether Camp’s four-valued semantics satisfies his own desiderata for a logic of confusion.

Philosophers on all sides of the contextualism debates have had an overly narrow conception of what semantic context sensitivity could be. They have conflated context sensitivity (dependence of truth or extension on features of context) with indexicality (dependence of content on features of context). As a result of this conflation, proponents of contextualism have taken arguments that establish only context sensitivity to establish indexicality, while opponents of contextualism have taken arguments against indexicality to be arguments against context sensitivity. Once these concepts are carefully pulled apart, it becomes clear that there is conceptual space in semantic theory for nonindexical forms of contextualism that have many advantages over the usual indexical forms.

If it is not now determined whether there will be a sea battle tomorrow, can an assertion that there will be one be true? The problem has persisted because there are compelling arguments on both sides. If there are objectively possible futures which would make the prediction true and others which would make it false, symmetry considerations seem to forbid counting it either true or false. Yet if we think about how we would assess the prediction tomorrow, when a sea battle is raging (or not), it seems we must assign the utterance a definite truth-value. I argue that both arguments must be given their due, and that this requires relativizing utterance-truth to a context of assessment. I show how this relativization can be handled in a rigorous formal semantics, and I argue that we can make coherent sense of assertion without assuming that utterances have their truth-values absolutely.

I argue for a new construal of Aristotle’s definition of anagnorisis (recognition) in Poetics 11. Virtually all translators and interpreters of the definition have understood the phrase ton pros eutuchian e dustuchian horismenon as a subjective genitive characterizing the persons involved in the recognition. I argue that it should instead be taken as a partitive genitive characterizing the genus of changes (metabolon) of which recognitions are a species. In addition to being preferable on philogical grounds, the construal I recommend helps illuminate the relation between recognition and reversal (peripeteia) and makes sense of Aristotle’s views about the relative values of various kinds of recognition.