What Is It to Make Clear the Working of Our Language?1

In The Logical Basis of Metaphysics, Dummett articulates and develops his “fundamental assumption” that the introduction rules for a logical constant determine its meaning. According to Dummett, logical laws in harmony with the introduction rules are justified, while logical laws not in harmony with the introduction rules are unjustified. This powerful picture enables Dummett to criticise certain aspects of our linguistic practice, such as the Law of Excluded Middle and the metaphysics of realism he believes it embodies, as not remaining responsible to the meanings of the logical constants. Against Dummett's fundamental assumption, I bring to bear what in the Tractatus Wittgenstein describes as his “fundamental thought” that the logical constants do not represent. Properly understood, Wittgenstein's point is that since the logical constants may be eliminated from the propositional signs of a fully precise logical notation, the constants do not express meanings to which our use of expressions containing the constants is responsible. I then apply Wittgenstein's fundamental thought to Dummett's proof‐theoretic notation to show that far from determining the meanings of the logical constants, the introduction rules merely allow the constants to be edited from certain inferences, leaving Dummett with no semantic kernel with which to criticise other sentences or inferences featuring the constants. Thus, his picture of what it is to make clear the working of our language collapses.     

Logic and Philosophy of Logic in Wittgenstein

This essay discusses Wittgenstein's conception of logic, early and late, and some of the types of logical system that he constructed. The essay shows that the common view according to which Wittgenstein had stopped engaging in logic as a philosophical discipline by the time of writing Philosophical Investigations is mistaken. It is argued that, on the contrary, logic continued to figure at the very heart of later Wittgenstein's philosophy; and that Wittgenstein's mature philosophy of logic contains many interesting thoughts that have gone widely unnoticed.     

Categorial Indeterminacy,Generality and Logical Form in Wittgenstein's Tractatus

Many commentators have attempted to say, more clearly than Wittgenstein did in his Tractatus logico‐philosophicus, what sort of things the ‘simple objects’ spoken of in that book are. A minority approach, but in my view the correct one, is to reject all such attempts as misplaced. The Tractarian notion of an object is categorially indeterminate: in contrast with both Frege's and Russell's practice, it is not the logician's task to give a specific categorial account of the internal structure of elementary propositions or atomic facts, nor, correlatively, to give an account of the forms of simple objects. The few commentators who have hitherto maintained this view have mainly devoted themselves to establishing that this was Wittgenstein's intention, and do not much address the question why Wittgenstein held that it is not the logician's business to say what the objects are. The present paper means to fill this lacuna by placing this view in the context of the Tractatus's treatment of logic generally, and in particular by connecting it with Wittgenstein's treatment of generality and with his reaction to Russell's approach to logical form.     

The power and the limits of Wittgenstein's N operator

The power of Wittgenstein's N operator described in the Tractatus is that every proposition which can be expressed in the Russellian variant of the predicate calculus familiar to him has an equivalent proposition in an extended variant of his N operator notation. This remains true if the bound variables are understood in the usual inclusive sense or in Wittgenstein's restrictive exclusive sense. The problematic limit of Wittgenstein's N operator comes from his claim that symbols alone reveal the logical status of propositions. This would require knowledge of the size of the Tractarian domain of unchangeable, simple objects, and this, Wittgenstein maintained, cannot be known.     

The End(s) of Philosophy: Rhetoric, Therapy and Wittgenstein's Pyrrhonism

In Culture and Value Wittgenstein remarks: ‘Thoughts that are at peace. That's what someone who philosophizes yearns for’. The desire for such conceptual tranquillity is a recurrent theme in Wittgenstein's work, and especially in his later ‘grammatical‐therapeutic’ philosophy. Some commentators (notably Rush Rhees and C. G. Luckhardt) have cautioned that emphasising this facet of Wittgenstein's work ‘trivialises’ philosophy – something which is at odds with Wittgenstein's own philosophical ‘seriousness’ (in particular his insistence that philosophy demands that one ‘Go the bloody hard way’). Drawing on a number of correlations between Wittgenstein's conception of philosophy and that of the Pyrrhonian Sceptics, in this paper I defend a strong ‘therapeutic’ reading of Wittgenstein, and show how this can be maintained without ‘trivialising’ philosophy.     

More than a feeling: Wittgenstein and William James on love and other emotions

One of the most significant features of Wittgenstein's Remarks on the Philosophy of Psychology (written after he had completed most of the Philosophical Investigations) is his reflections on emotions. Wittgenstein's treatment of this topic was developed in direct response to his reading of William James’s chapter on emotions in his 1890 masterpiece, The Principles of Psychology. This paper examines the competing views of emotions that emerge in these works, both of which attempt to overcome the Cartesian dualist conception in different ways. The main point of disagreement concerns the relation between emotions and their bodily expression (e.g. the relation between grief and weeping). My interpretation focuses on Wittgenstein's remarks on the emotion of love because, I argue, it is a particularly problematic case. To elucidate his largely unexplored view of love, I draw on his remarks on understanding and criteria in the Philosophical Investigations. I argue that by examining the examples of complex emotions like love, we can arrive at a more accurate characterization of Wittgenstein's general view of mental concepts and mental phenomena.     

A Lewisian Semantics for S2

This paper sets out a semantics for C.I. Lewis's logic S2 based on the ontology of his 1923 paper ‘Facts, Systems, and the Unity of the World’. In that article, worlds are taken to be maximal consistent systems. A system, moreover, is a collection of facts that is closed under logical entailment and conjunction. In this paper, instead of defining systems in terms of logical entailment, I use certain ideas in Lewis's epistemology and philosophy of logic to define a class of models in which systems are taken to be primitive elements but bear certain relations to one another. I prove soundness and completeness for S2 over this class of models and argue that this semantics makes sense of at least a substantial fragment of Lewis's logical theory.     

"This is Simply What I Do"

Wittgenstein's discussion of rule‐following is widely regarded to have identified what Kripke called “the most radical and original sceptical problem that philosophy has seen to date”. But does it? This paper examines the problem in the light of Charles Peirce's distinctive scientific hierarchy. Peirce identifies a phenomenological inquiry which is prior to both logic and metaphysics, whose role is to identify the most fundamental philosophical categories. His third category, particularly salient in this context. pertains to general predication. Rule‐following scepticism, the paper suggests, results from running together two questions: “How is it that I can project rules?”, and, “What is it for a given usage of a rule to be right?”. In Peircean terms the former question, concerning the irreducibility of general predication (to singular reference), must be answered in phenomenology, while the latter, concerning the difference between true and false predication, is answered in logic. A failure to appreciate this distinction, it is argued, has led philosophers to focus exclusively on Wittgenstein's famous public account of rule‐following rightness, thus overlooking a private, phenomenological dimension to Wittgenstein's remarks on following a rule which gives the lie to Kripke's reading of him as a sceptic.     

Was Wittgenstein an Epistemic Relativist?1

The paper reviews the grounds for relativist interpretations of Wittgenstein's later thought, especially in On Certainty. It distinguishes between factual and virtual forms of epistemic relativism and argues that, on closer inspection, Wittgenstein's notes don't support any form of relativism – let it be factual or virtual. In passing, it considers also so‐called “naturalist” readings of On Certainty, which may lend support to a relativist interpretation of Wittgenstein's ideas, finds them wanting, and recommends to interpret his positive proposal in On Certainty as a form of “internal rationalism.”     

A Debate About Anderson's Logic

This article is about the history of logic in Australia. Douglas Gasking (1911–1994) undertook to translate the logical terminology of John Anderson (1893–1962) into that of Ludwig Wittgenstein's (1921) Tractatus. At the time Gilbert Ryle (1900–1976), and more recently David Armstrong, recommended the result to students; but it is reasonable to have misgivings about Gasking as a guide to either Anderson or Wittgenstein. The historical interest of the debate Gasking initiated is that it yielded surprisingly little information about Anderson's traditional (syllogistic or Aristotelian) logic and its relation to classical (first-order predicate or Russellian) logic, the ostensible topic; but the materials now exist to interpret Anderson's logic in classical logic, possibly as an algebra of classes. This would be of little interest to contemporary logicians, but it might shed some light on Anderson's philosophy.     

The Tractatus on Logical Consequence

Abstract: I discuss the account of logical consequence advanced in Wittgenstein's Tractatus. I argue that the role that elementary propositions are meant to play in this account can be used to explain two remarkable features that Wittgenstein ascribes to them: that they are logically independent from one another and that their components refer to simple objects. I end with a proposal as to how to understand Wittgenstein's claim that all propositions can be analysed as truth functions of elementary propositions.     

The Influence of Einstein on Wittgenstein's Philosophy

On the basis of historical and textual evidence, this paper claims that (i) after his Tractatus, Wittgenstein was actually influenced by Einstein's theory of relativity and, (ii) the similarity of Einstein's relativity theory helps to illuminate some aspects of Wittgenstein's work. These claims find support in remarkable quotations where Wittgenstein speaks approvingly of Einstein's relativity theory and in the way these quotations are embedded in Wittgenstein's texts. The profound connection between Wittgenstein and relativity theory concerns not only Wittgenstein's “verificationist” phase (more closely connected with Schlick's work), but also Wittgenstein's later philosophy centred on the theme of rule‐following.     

Wittgenstein and logical necessity

An attempt is made to show that Wittgenstein's later philosophy of logic is not the kind of conventionalism which is often ascribed to him. On the contrary, Wittgenstein gives expression to a “mixed” theory which is not only interesting but tends to resolve the perplexities usually associated with the question of the a priori character of logical truth. I try to show that Wittgenstein is better understood not as denying that there are such things as “logical rules” nor as denying that the results of applying such rules are “logically necessary,” but as trying to understand what it is to appeal to a logical rule and what it means to say that the results of applying such a rule are “necessary.” He is not so much overthrowing standard accounts of logical necessity as discovering the limits of the concept.     

Completeness: from Gödel to Henkin

This paper focuses on the evolution of the notion of completeness in contemporary logic. We discuss the differences between the notions of completeness of a theory, the completeness of a calculus, and the completeness of a logic in the light of Gödel's and Tarski's crucial contributions.We place special emphasis on understanding the differences in how these concepts were used then and now, as well as on the role they play in logic. Nevertheless, we can still observe a certain ambiguity in the use of the close notions of completeness of a calculus and completeness of a logic. We analyze the state of the art under which Gödel's proof of completeness was developed, particularly when dealing with the decision problem for first-order logic. We believe that Gödel had to face the following dilemma: either semantics is decidable, in which case the completeness of the logic is trivial or, completeness is a critical property but in this case it cannot be obtained as a corollary of a previous decidability result. As far as first-order logic is concerned, our thesis is that the contemporary understanding of completeness of a calculus was born as a generalization of the concept of completeness of a theory. The last part of this study is devoted to Henkin's work concerning the generalization of his completeness proof to any logic from his initial work in type theory.     

Instructions for Climbing the Ladder (The Minimalism of Wittgenstein's Tractatus)

I aim to present a solution to the apparent paradox of the Tractatus by means of a minimalist reading grounded in the idea that the correct logical symbolism alone “finally solves” in essentials the philosophical problems. I argue that although the sentences of the Tractatus are nonsensical, rules presented in its symbolism are not. The symbolism itself expresses only a priori rules of logic through schematic variables that do not say anything. I argue that this reading correctly expresses the ladder structure of the book, and that it can account for Wittgenstein's critique of the Tractatus in Some Remarks on Logical Form.     

An Illocutionary Logical Explanation of the Surprise Execution

This paper further develops the system of illocutionary logic presented in ‘Propositional logic of supposition and assertion’ (Notre Dame Journal of Formal Logic 1997, 38, 325-349) to accommodate an ‘I believe that’ operator and resolve Moore's Paradox. This resolution is accomplished by providing both a truth-conditional and a commitment-based semantics. An important feature of the logical system is that the correctness of some arguments depends on who it is that makes the argument. The paper then shows that the logical system can be expanded to resolve the surprise execution paradox puzzle. The prisoner's argument showing that he can't be executed by surprise is correct but his beliefs are incoherent. The judge's beliefs (and our beliefs) about this situation are not incoherent.     

Abstraction in Fitch's Basic Logic

Fitch's basic logic is an untyped illative combinatory logic with unrestricted principles of abstraction effecting a type collapse between properties (or concepts) and individual elements of an abstract syntax. Fitch does not work axiomatically and the abstraction operation is not a primitive feature of the inductive clauses defining the logic. Fitch's proof that basic logic has unlimited abstraction is not clear and his proof contains a number of errors that have so far gone undetected. This paper corrects these errors and presents a reasonably intuitive proof that Fitch's system K supports an implicit abstraction operation. Some general remarks on the philosophical significance of basic logic, especially with respect to neo-logicism, are offered, and the paper concludes that basic logic models a highly intensional form of logicism.     

On Wittgenstein's Kantian solution of the problem of philosophy

In 1931 Wittgenstein wrote: ‘the limit of language manifests itself in the impossibility of describing the fact that corresponds to (is the translation of) a sentence without simply repeating the sentence’. Here, Wittgenstein claims, ‘we are involved?…?with the Kantian solution of the problem of philosophy’. This paper shows how this remark fits with Wittgenstein's early account of the substance of the world, his account of logic, and ultimately his view of philosophy. By contrast to the currently influential resolute reading of the Tractatus, the paper argues that the early Wittgenstein did not aim at destroying the idea of a limit of language, but that the notion lies at the very heart of Wittgenstein's early view. In doing so, the paper employs and defends the Kantian interpretation of Wittgenstein's early philosophy.