Dieser Band enthält die vier Arbeiten Freges: Begriffsschrift, eine der arithmetischen nachgebildeten Formelsprache, 1879; Anwendungen der Begriffsschrift, 1879; Über den Briefwechsel Leibnizens und Huggens mit Papin, 1881; Über den Zweck der Begriffsschrift, 1883; Über die wissenschaftliche Berechtigung einer Begriffsschrift, 1882. Frege's research work in the field of mathematical logic is of great importance for the present-day analytic philosophy. We actually owe to Frege a great amount of basical insight and exemplary research, which set up a new standard also (...) in other fields of knowledge. As the founder of mathematical logic he severely examindes the syllogisms on which arithmetic is built up. In doing so, Frege recognized that our colloquial language is inadequate to define logic structures. His notional language corresponded to the artaivicial logical language demandes by Leibniz. Frege's achievement in the field of logic were so important, that they radiated into the domain of philosophy and influenced the development of mathematical logic decisively. (shrink)

In this paper, we study a concept of universe for a truth predicate over applicative theories. A proof-theoretic analysis is given by use of transfinitely iterated fixed point theories . The lower bound is obtained by a syntactical interpretation of these theories. Thus, universes over Frege structures represent a syntactically expressive framework of metapredicative theories in the context of applicative theories.

Call a family F of subsets of a set E inductive if ∅ ∈ F and F is closed under unions with disjoint singletons, that is, if ∀X∈F ∀x∈E–X(X ∪ {x} ∈ F]. A Frege structure is a pair (E.

Dieser Band enthält die vier Arbeiten Freges: Begriffsschrift, eine der arithmetischen nachgebildeten Formelsprache, 1879; Anwendungen der Begriffsschrift, 1879; Über den Briefwechsel Leibnizens und Huggens mit Papin, 1881; Über den Zweck der Begriffsschrift, 1883; Über die wissenschaftliche Berechtigung einer Begriffsschrift, 1882. Frege's research work in the field of mathematical logic is of great importance for the present-day analytic philosophy. We actually owe to Frege a great amount of basical insight and exemplary research, which set up a new standard also (...) in other fields of knowledge. As the founder of mathematical logic he severely examindes the syllogisms on which arithmetic is built up. In doing so, Frege recognized that our colloquial language is inadequate to define logic structures. His notional language corresponded to the artaivicial logical language demandes by Leibniz. Frege's achievement in the field of logic were so important, that they radiated into the domain of philosophy and influenced the development of mathematical logic decisively. (shrink)

In this paper we summarize some results about sets in Frege structures. The resulting set theory is discussed with respect to its historical and philosophical significance. This includes the treatment of diagonalization in the presence of a universal set.

The idea that thoughts are structured is essential to Frege's understanding of thoughts. A basic tenet of his thinking was that the structure of a sentence can serve as a model for the structure of a thought. Recent commentators have, however, identified tensions between that principle and certain other doctrines Frege held about thoughts. This paper suggests that the tensions identified by Dummett and Bell are not really tensions at all. In establishing the case against Dummett and Bell (...) the paper argues (a) that Frege was committed, in virtue of his doctrine of decomposition, to the thesis that a single sentence can express a range of thoughts, and (b) that Frege was committed, in virtue of his views about truth, to the thesis that a single thought can be expressed by structurally different sentences. But neither of these theses comes into conflict with the basic principle. (shrink)

There is a parallel between the debate between Gottlob Frege and David Hilbert at the turn of the twentieth century and at least some aspects of the current controversy over whether category theory provides the proper framework for structuralism in the philosophy of mathematics. The main issue, I think, concerns the place and interpretation of meta-mathematics in an algebraic or structuralist approach to mathematics. Can meta-mathematics itself be understood in algebraic or structural terms? Or is it an exception to (...) the slogan that mathematics is the science of structure? (shrink)

This paper attempts to confine the preconceptions that prevented Frege from appreciating Hilbert?s Grundlagen der Geometrie to two: (i) Frege?s reliance on what, following Wilfrid Hodges, I call a Frege?Peano language, and (ii) Frege?s view that the sense of an expression wholly determines its reference.I argue that these two preconceptions prevented Frege from achieving the conceptual structure of model theory, whereas Hilbert, at least in his practice, was quite close to the model?theoretic point of view.Moreover, (...) the issues that divided Frege and Hilbert did not revolve around whether one or the other allowed metalogical notions.Frege, e.g., succeeded in formulating the notion of logical consequence, at least to the extent that Bolzano did; the point is rather that even though Frege had certain semantic concepts, he did not articulate them model?theoretically, whereas, in some limited sense, Hilbert did. (shrink)

Fregean thoughts (i.e. the senses of assertoric sentences) are structured entities because they are composed of simpler senses that are somehow ordered and interconnected. The constituent senses form a unity because some of them are ?saturated? and some ?unsaturated?. This paper shows that Frege's explanation of the structure of thoughts, which is based on the ?saturated/unsaturated? distinction, is by no means sufficient because it permits what I call ?wild analyses?, which have certain unwelcome consequences. Wild analyses are made possible (...) because any ?unsaturated? sense that is a mode of presentation of a concept together with any ?saturated? sense forms a thought. The reason is that any concept can be applied to any object (which is presented by a ?saturated? sense). This stems from the fact that Frege was willing to admit only total functions. It is also briefly suggested what should be done to block wild analyses. (shrink)

We set out the implication fragment of Frege’s Grundgesetze, clarifying the implication rules and showing that this system extends Absolute Implication, or the implication fragment of Intuitionist logic. We set out a sequent calculus which naturally captures Frege’s implication proofs, and draw particular attention to the Cut-like features of his Hypothetical Syllogism rule.

In the opening sentence of his Methods of Logic, W. V. O. Quine writes, “Logic is an old subject, and since 1879 it has been a great one.”1 Quine is referring to the year in which Gottlob Frege presented his Begriffschrift, or “concept-script,” one of the first published accounts of a logical system or calculus with quantification and a function-argument analysis of propositions. There can be no doubt as to the importance of these introductions, and, indeed, Frege’s orientation (...) and advances, if not his particular system, have proven to be highly significant for much of mathematical logic and research pertaining to the foundations of mathematics. Nevertheless, Quine’s assessment, often repeated, obscures other.. (shrink)

So-called 'Frege cases' pose a challenge for anyone who would hope to treat the contents of beliefs (and similar mental states) as Russellian propositions: It is then impossible to explain people's behavior in Frege cases without invoking non-intentional features of their mental states, and doing that seems to undermine the intentionality of psychological explanation. In the present paper, I develop this sort of objection in what seems to me to be its strongest form, but then offer a response (...) to it. I grant that psychological explanation must invoke non-intentional features of mental states, but it is of crucial importance which such features must be referenced. -/- It emerges from a careful reading of Frege's own view that we need only invoke what I call 'formal' relations between mental states. I then claim that referencing such 'formal' relations within psychological explanation does not undermine its intentionality in the way that invoking, say, neurological features would. The central worry about this view is that either (a) 'formal' relations bring narrow content in through back door or (b) 'formal' relations end up doing all the explanatory work. Various forms of each worry are discussed. The crucial point, ultimately, is that the present strategy for responding to Frege cases is not available either to the 'psycho-Fregean', who would identify the content of a belief with its truth-value, nor even to someone who would identify the content of a belief with a set of possible worlds. It requires the sort of rich semantic structure that is distinctive of Russellian propositions. There is therefore no reason to suppose that the invocation of 'formal' relations threatens to deprive content of any work to do. (shrink)

A logically perfect language must meet following requirements: (i) it must not contain „empty“ expressions designating nothing and (ii) it must not involve phrases that are synonymous, homonymous etc. According to Frege, the meaning of a compound expression is a function of meanings of its components, i.e. the meaning of an expression consisting of a functional phrase and a name is the value of the function for the argument. However, for some arguments a function need not give values and, (...) hence, some compound phrases designate nothing in spite of the fact that every simple expression does designate something. Frege’s construction of a logically perfect language fails because it violates condition (i). According to Wittgenstein, every language is logically perfect; otherwise it cannot represent the world. Every expression, simple or compound, does designate something; the meaning of a compound expression consists of meanings of its components; the structure of a complex expression’s meaning mirrors, when completely analysed, the syntactic structure of the expression. Wittgenstein distinguishes between language and notation and we are supposed to look for a logically perfect notation that does not contain homonymy or synonymy. However, following some ideas from Tractatus, it can be shown that Wittgenstein cannot eliminate these phenomena and, hence, violates condition (ii). (shrink)

In this short monograph, John Horty explores the difficulties presented for Gottlob Frege's semantic theory, as well as its modern descendents, by the treatment of defined expressions. The book begins by focusing on the psychological constraints governing Frege's notion of sense, or meaning, and argues that, given these constraints, even the treatment of simple stipulative definitions led Frege to important difficulties. Horty is able to suggest ways out of these difficulties that are both philosophically and logically plausible (...) and Fregean in spirit. This discussion is then connected to a number of more familiar topics, such as indexicality and the discussion of concepts in recent theories of mind and language. In the latter part of the book, after introducing a simple semantic model of senses as procedures, Horty considers the problems that definitions present for Frege's idea that the sense of an expression should mirror its grammatical structure. The requirement can be satisfied, he argues, only if defined expressions--and incomplete expressions as well--are assigned senses of their own, rather than treated contextually. He then explores one way in which these senses might be reified within the procedural model, drawing on ideas from work in the semantics of computer programming languages. With its combination of technical semantics and history of philosophy, Horty's book tackles some of the hardest questions in the philosophy of language. It should interest philosophers, logicians, and linguists. (shrink)

Frege's Grundgesetze was one of the 19th century forerunners to contemporary set theory which was plagued by the Russell paradox. In recent years, it has been shown that subsystems of the Grundgesetze formed by restricting the comprehension schema are consistent. One aim of this paper is to ascertain how much set theory can be developed within these consistent fragments of the Grundgesetze, and our main theorem shows that there is a model of a fragment of the Grundgesetze which defines (...) a model of all the axioms of Zermelo-Fraenkel set theory with the exception of the power set axiom. The proof of this result appeals to G\"odel's constructible universe of sets, which G\"odel famously used to show the relative consistency of the continuum hypothesis. More specifically, our proofs appeal to Kripke and Platek's idea of the projectum within the constructible universe as well as to a weak version of uniformization (which does not involve knowledge of Jensen's fine structure theory). The axioms of the Grundgesetze are examples of abstraction principles, and the other primary aim of this paper is to articulate a sufficient condition for the consistency of abstraction principles with limited amounts of comprehension. As an application, we resolve an analogue of the joint consistency problem in the predicative setting. (shrink)

We draw attention to a series of implicit assumptions that have structured the debate about Frege’s Puzzle. Once these assumptions are made explicit, we rely on them to show that if one focuses exclusively on the issues raised by Frege cases, then one obtains a powerful consideration against a fine-grained conception of propositional-attitude content. In light of this consideration, a form of Russellianism about content becomes viable.

What is the relationship between Frege’s puzzle and the puzzle of the de se? An increasingly influential view claims that the de se puzzle is merely an instance of Frege’s puzzle and that the idea that de se attitudes pose a distinctive theoretical challenge rests on a myth. Here we argue that this view is misguided. There are important differences between the two puzzles. First, unlike Frege puzzle cases, de se puzzle cases involve unshareable Fregean senses. Second, (...) unlike Frege puzzle cases, de se puzzle cases cannot be resolved by objective information alone. Further, there seem to be pure cases of each puzzle: instances of the de se puzzle which do not have a Fregean structure, and instances of Frege’s puzzle, which do not involve de se attitudes. We conclude that the two puzzles are fundamentally different and that the traditional theory of attitudes needs to be amended. (shrink)

I investigate why Frege rejected the theory of types, as Russell presented it to him in their correspondence. Frege claims that it commits one to violations of the law of excluded middle, but this complaint seems to rest on a dogmatic refusal to take Russell’s proposal seriously on its own terms. What is at stake is not so much the truth of a law of logic, but the structure of the hierarchy of the logical categories, something Frege (...) seems to neglect. To come to a better understanding of Frege’s response, I proceed to investigate his conception of the nature of the logical categories, and how it differs from Russell’s. I argue that, for Frege, our grasp of the logical categories cannot be severed from our grasp of the Begriffsschrift notation itself. Russell, on the other hand, attaches no such importance to notation. From Frege’s point of view, Russell has not succeeded in presenting an alternative conception of the logical hierarchy, since such a conception must go in tandem with the development of a notation. Moreover, Frege has good reasons to think that Russell’s proposal does not admit of a suitable notation. (shrink)

Frege's docent's dissertation Rechnungsmethoden, die sich auf eine Erweiterung des Grössenbegriffes gründen(1874) contains indications of a bold attempt to extend arithmetic. According to it, arithmetic means the science of magnitude, and magnitude must be understood structurally without intuitive support. The main thing is insight into the formal structure of the operation of ?addition?. It turns out that a general ?magnitude domain? coincides with a (commutative) group. This is an interesting connection with simultaneous developments in abstract algebra. As his main (...) application, Frege studies iterations of functions. He does not yet pose the question of existence proofs. Measurement of magnitudes is also connected to numbers, but the discussion is here ambiguous in a way which calls for the systematic account of numbers in Grundgesetze. (shrink)

Frege puzzles exploit cognitive differences between co-referential terms. Traditionally, they were handled by some version of Frege’s distinction between sense and reference, which avoided disruptive consequences for epistemology. However, the Fregean programme did not live up to its original promise, and was undermined by the development of theories of direct reference; for semantic purposes, its prospects now look dim. In particular, well-known analogues of Frege puzzles concern pairs of uncontentious synonyms; attempts to deal with them by distinguishing (...) idiolects or postulating ‘narrow contents’ or elaborate forms of context-sensitivity are inadequate or semantically implausible. Although ascriptions of knowledge, belief, and other attitudes are ubiquitous in epistemology, epistemologists have not properly come to terms with the surprising consequences of anti-Fregean semantic accounts of attitude ascriptions. In ‘A Puzzle about Belief ’, Saul Kripke shows that natural-seeming disquotational principles for ascribing belief lead to apparently unacceptable consequences, including outright contradictions, in problem cases. Such disquotation principles, I argue, are best regarded not as conceptual connections but just as heuristics in the psychological sense, quick and easy ways of assessing belief ascriptions, usually accurate under normal conditions but far from 100% reliable. I discuss similar heuristics for ascribing knowledge and other attitudes. That the principles have a merely heuristic status need not be pre-theoretically manifest to their users. This view vindicates Kripke’s conclusion that it would be wrong-headed to draw semantic conclusions from Frege puzzles. I discuss the epistemological consequences of an anti-Fregean approach to Frege puzzles, including for Kripke’s cases of the contingent a priori and the necessary a posteriori, but also for evidence, for epistemic modalities, and for epistemic and subjective conceptions of probability. Anna Mahtani’s recent identification of Frege puzzles for the ex ante Pareto Principle as used in welfare economics provides an interesting example. I suggest a model-building methodology as the most promising way of handling at least some of the difficulties. A final issue is the choice between different anti-Fregean approaches to semantics, from very coarse-grained intensional approaches on which sentences express functions from possible worlds to truth-values to more fine-grained hyperintensional approaches on which sentences express functions from possible or impossible worlds to truth-values or else Russellian structured propositions. Some of the hyperintensional theories violate semantic compositionality. More generally, since our attitude ascriptions rely on heuristics, they should be expected to exhibit some level of error; although hyperintensional approaches may be able slightly to reduce the level of postulated error, they do so at the cost of vastly increased theoretical complexity, and so have weak explanatory power. Methodologically, a simple intensional approach does better. (shrink)

This paper casts doubt on a recent criticism of Frege's theory of concepts and extensions by showing that it misses one of Frege's most important contributions: the derivation of the infinity of the natural numbers. We show how this result may be incorporated into the conceptual structure of Zermelo- Fraenkel Set Theory. The paper clarifies the bearing of the development of the notion of a real-valued function on Frege's theory of concepts; it concludes with a brief discussion (...) of the claim that the standard interpretation of second-order logic is necessary for the derivation of the Peano Postulates and the proof of their categoricity. (shrink)

It is widely believed that some puzzling and provocative remarks that Frege makes in his late writings indicate he rejected independence arguments in geometry, particularly arguments for the independence of the parallels axiom. I show that this is mistaken: Frege distinguished two approaches to independence arguments and his puzzling remarks apply only to one of them. Not only did Frege not reject independence arguments across the board, but also he had an interesting positive proposal about the logical (...) structure of correct independence arguments, deriving from the geometrical principle of duality and the associated idea of substitution invariance. The discussion also serves as a useful focal point for independently interesting details of Frege's mathematical environment. This feeds into a currently active scholarly debate because Frege's supposed attitude to independence arguments has been taken to support a widely accepted thesis (proposed by Ricketts among others) concerning Frege's attitude toward metatheory in general. I show that this thesis gains no support from Frege's puzzling remarks about independence arguments. (shrink)

Frege’s writings contain arguments for the thesis (i) that a thought expressed by a sentence S is a structured object whose composition pictures the composition of S, and for the thesis (ii) that a thought is an unstructured object. I will argue that Frege’s reasons for both (i) and (ii) are strong. Frege’s explanation of the difference in sense between logically equivalent sentences rests on assumption (i), while Frege’s claim that the same thought can be decomposed (...) differently makes (ii) plausible. Thoughts are supposed to do work that requires that they be structured and work that requires that they be unstructured. But this cannot be! While the standard response to this problem is to reject either (i) or (ii), I propose a charitable repair in the spirit of Frege’s theory that accepts both. The key idea can be found in Frege’s Basic Laws of Arithmetic(BL, GGA). Frege argues that the thought expressed by a sentence is determined by the truth-conditions that can be derived from the semantic axioms for the sentence constituents. The fact that the same axiomatic truth-condition can be derived in different ways from different semantic axioms suggests a Fregean solution of the dilemma: A thought is a type that is instantiated by all sequences of senses (decomposed thoughts) that have the same axiomatic truth-conditions. This allows for multiple decomposability of the same thought (for different decomposed thoughts can have the same axiomatic truth-conditions) and for a notion of containment (the decomposed thought contains those senses whose semantic axioms are needed in the derivation of the truth-conditions). My proposal combines the virtues of (i) and (ii) without inheriting their vices. (shrink)

Gottlob Frege may be considered as the first intellectual giant in thePhilosophy of Language. He was the first to raise the issue ofmeaning by formulating an organized theory of meaning for a part ofnatural language as the theory of meaning is at the core of philosophy of language. He emphasizes that the meaning of a sentence directly depends on the meaning of its constituent parts. That is why he has to dissect the internal structure of a sentence or complex (...) expressions provided by a logical syntax, while the truth value of such sentences may be revealed by logical semantics which can be put forward by treating these sentences as a whole. (shrink)

I investigate the role of geometric intuition in Frege’s early mathematical works and the significance of his view of the role of intuition in geometry to properly understanding the aims of his logicist project. I critically evaluate the interpretations of Mark Wilson, Jamie Tappenden, and Michael Dummett. The final analysis that I provide clarifies the relationship of Frege’s restricted logicist project to dominant trends in German mathematical research, in particular to Weierstrassian arithmetization and to the Riemannian conceptual/geometrical tradition (...) at Göttingen. Concurring with Tappenden, I hold that Frege’s logicism should not be understood as a continuing a project of reductionist arithmetization. However, Frege does not quite take up the Riemannian banner either. His logicism supports a hierarchical understanding of the structure of mathematical knowledge, according to which arithmetic is applicable to geometry but not vice versa because the former is more general, as revealed by the strictly logical nature of its objects in comparison to the intuitional nature of geometric objects. I suggest, in particular, that Frege intended that foundational work would show the use of geometric intuition in complex analysis, a source of error for Riemann that Weierstrass was proud to have uncovered, to be inessential. (shrink)

In this paper, I critically discuss Frege’s philosophy of geometry with special emphasis on his position in The Foundations of Arithmetic of 1884. In Sect. 2, I argue that that what Frege calls faculty of intuition in his dissertation is probably meant to refer to a capacity of visualizing geometrical configurations structurally in a way which is essentially the same for most Western educated human beings. I further suggest that according to his Habilitationsschrift it is through spatial intuition (...) that we come to know the axioms of Euclidean geometry. In Sect. 3, I argue that Frege seems right in claiming in The Foundations, §14 that the synthetic nature of the Euclidean axioms follows from the fact that they are independent of one another and of the primitive laws of logic. If the former were dependent on the latter, they would be analytic in Frege’s sense of analyticity. But then they would not be independent of one another and due to their mutual provability would lose their status as axioms of Euclidean geometry, since according to Frege an axiom of a theory T is per definitionen unprovable in T. I further argue that only by invoking pure spatial intuition can Frege “explain” the epistemological status of the axioms of Euclidean geometry completely: their synthetic a priori nature. Finally, I argue that his view about independence in The Foundations, §14 seems to clash with his conception of independence in his mature period. In Sect. 4, I scrutinize Frege’s somewhat vague, but unduly neglected remarks in The Foundations, §26 on space, spatial intuition and the axioms of Euclidean geometry. I argue that for the sake of coherence Frege should have said unambiguously that space is objective, that it is independedent not only of our spatial intuition, but of our mental life altogether including our judgements about space, instead of encouraging the possible conjecture that in his view it contains an objective and a subjective component. I further argue that for Frege the objectivity of both space and the axioms of Euclidean geometry manifests itself in our universal and compulsory acknowledgement of the Euclidean axioms as true. I conclude Sect. 4 by arguing that there is a conflict between the subjectivity of our spatial intuitions as stressed in The Foundations, §26 and Frege’s thesis in his dissertation that the axioms of Euclidean geometry derive their validity from the nature of our faculty of intuition. To resolve this conflict, I propose that in the light of his avowed realism in The Foundations Frege could have replaced his early thesis by saying that although we come to know the axioms of Euclidean geometry through spatial intuition and are justified in acknowledging them as true on the basis of geometrical intuition, their truth is independent not only of the nature of our faculty of intuition and singular acts of intuition, but of our mental processes and activities in general, including the inner mental act of judging. In Sect. 5, I argue that Frege most likely did not adopt Kant’s method of acquiring geometrical knowledge via the ostensive construction of concepts in spatial intuition. In contrast to Kant, Frege holds that the axioms of three-dimensional Euclidean geometry express state of affairs about space obtaining independently of our spatial intuition. In Sect. 6, I conclude with a summarized assessment of Frege’s philosophy of geometry. (shrink)

There are mathematical structures with elements that cannot be distinguished by the properties they have within that structure. For instance within the field of complex numbers the two square roots of −1, i and −i, have the same algebraic properties in that field. So how do we distinguish between them? Imbedding the complex numbers in a bigger structure, the quaternions, allows us to algebraically tell them apart. But a similar problem appears for this larger structure. There seems to be (...) always a background and a context that we rely upon. Thus mathematicians naturally make use of Kantian intuition and references fixed by names and denotations. I argue that such features cannot be avoided. (shrink)

According to act theories, propositions are structured cognitive act‐types. Act theories appear to make propositions inherently representational and truth‐evaluable, and to provide solutions to familiar problems with alternative theories, including Frege’s and Russell’s problems, and the third‐realm and unity problems. Act theories have critical problems of their own, though: acts as opposed to their objects are not truth evaluable, not structured in the right way, not expressed by sentences, and not the objects of propositional attitudes. I show how identifying (...) propositions with other cognitive event‐types, namely thoughts, has the perceived virtues of act theories without the defects. (shrink)

This paper identifies a tension in Frege’s philosophy and offers a diagnosis of its origins. Frege’s Context Principle can be used to dissolve the problem of propositional unity. However, Frege’s official response to the problem does not invoke the Context Principle, but the distinction between ‘saturated’ and ‘unsaturated’ propositional constituents. I argue that such a response involves assumptions that clash with the Context Principle. I suggest, however, that this tension is not generated by deep-seated philosophical commitments, but (...) by Frege’s occasional attempt to take a dubious shortcut in the justification of his conception of propositional structure. (shrink)

Wittgenstein afirma no Tractatus que a teoria das classes é supérflua na Matemática e que isso está relacionado ao fato de que a generalidade exigida pela Matemática não é “acidental” (TLP 6.031). O objetivo deste texto é elucidar essa afirmação chamando a atenção para o que, seguindo Gregory Landini, tomaremos como uma forma de Logicismo compartilhada por Frege e Russell. Esta forma de Logicismo tem dois princípios básicos, a saber: o uso de uma teoria lógica cujas variáveis estruturadas incorporam (...) o que hoje chamamos de teoria dos tipos simples e a análise de atribuições numéricas em termos de afirmações sobre conceitos ou atributos que empregam conceitos de ordem superior exatamente análogos aos chamados quantificadores ‘numericamente definidos’. Argumentamos que é esse arcabouço teórico que Wittgenstein está rejeitando em 6.031 e não apenas o uso da Teoria dos Conjuntos na Matemática. Também é defendido que a noção de classe ainda tem um papel essencial a desempenhar no Tractatus.AbstractWittgenstein claims in the Tractatus that the theory of classes is superfluous in Mathematics and that this is related to the fact that the generality required by Mathematics is not “accidental” (TLP 6.031). My aim in this paper is to elucidate this claim by calling attention to what, following Gregory Landini, I refer to as a form of Logicism shared by Frege and Russell. This form of Logicism has two main tenets, namely:the use of a logical theory whose structured variables embody what we nowadays call the simple theory of types and the analysis of number ascriptions in terms of assertions about concepts or attributes which employ higher-order concepts exactly analogous to so-called ‘numerically definite’ quantifiers. It is argued that it is this shared theoretical framework that Wittgenstein is rejecting in 6.031 and not just the use of Set Theory in Mathematics. It is also argued that the notion of class still has an essential role to play in the Tractatus. (shrink)

This article treats three aspects of Frege's discussions of definitions. First, I survey Frege's main criticisms of definitions in mathematics. Second, I consider Frege's apparent change of mind on the legitimacy of contextual definitions and its significance for recent neo-Fregean logicism. In the remainder of the article I discuss a critical question about the definitions on which Frege's proofs of the laws of arithmetic depend: do the logical structures of the definientia reflect the understanding of (...) arithmetical terms prevailing prior to Frege's analyses? Unless they do, it is unclear how Frege's proofs demonstrate the analyticity of the arithmetic in use before logicism. Yet, especially in late writings, Frege characterizes definitions as arbitrary stipulations of the senses or references of expressions unrelated to pre-definitional understanding. I conclude by examining some options for conceiving of the status of Frege's logicism in light of this apparent tension, and outline a suggestion for a philosophically fruitful way of resolving this tension. (shrink)

This paper considers the role of constitutivity and normativity in Frege’s conception of logic. It outlines an historical interpretation with two goals. First, it traces these concepts back to their origins in Kant’s philosophy. Second, it considers some of the different ways in which the issue of normativity and its proper grounding was addressed in the neo-Kantian tradition and in early analytic philosophy. Some neo-Kantians worked out an epistemic-normative conception of objective judgment, according to which the objectivity of cognition (...) is constituted by distinctively logical norms. In Frege we find an original and sophisticated version of this line of thought. For Frege, the normative and constitutive roles of logic come to the fore in the articulation of scientific reason which follows the classical model of demonstrative science as cognitio ex principiis. Wittgenstein’s Tractatus then opens up a fresh Kantian perspective on the constitutivity of logic, one that grounds logic in structure rather than norms, and does so in conscious opposition to Frege and his normative science. Logic is transcendental, according to Wittgenstein, being the essence of the world and of all description. Hence, the normative function of logic becomes, in a way, superfluous. (shrink)

The similarity between logic and semantics of the Stoics and Frege has long been known, and it can be explained in various ways. In 2021, Susane Bobzien published a work in which she explains this similarity rather surprisingly: she hypothesizes that Frege generously helped himself with the foundations of Stoic logic as it was published in the first volume of History of Logic in the West by Carl Prantl. However, this hypothesis encounters various problems. The key point of (...) the whole accusation is founded on the formulation of a general propo-sition in language using implication and anaphora, which Frege supposedly took from the Stoics, although in Prantl’s text there is only one example of a sentence with this structure. On the contrary, there are many examples of such sentences in contemporary professional (e.g. legal) texts. Many examples of semantic simi-larities that Bobzien presents are based only on the similarities between isolated concepts; however, that is regularly the case for such concepts with the same conceptual basis. Bobzien presents a significant number of matches only on the basis of results that could allegedly be inferred from the texts. However, this cannot be considered a proof of plagiarism. Bobzien does not consider many sources for the continuity of interpretation such as the so-called hypothetical syllogism found in available textbooks of logic. Last but not least, her claims do not consider many differences between Stoic and Frege’s logic. All this leads us to the conclusion that Bobzien does not present sufficient facts and connections between them that would confirm her hypothesis about Frege’s plagiarism of the Stoic logic: Frege simply was not a plagiarist. (shrink)

One of the most pressing issues in contemporary semantics is whether propositions are structured entities that should be individuated in terms of their components or, contrarily, they lack structure and should be individuated in terms of their inferential relations. Another one is whether propositions should always contain all the information that is needed to deem them true or false—whether they should always be Fregean propositions. The latter debate might seem to presuppose a certain position in the former. However, it is (...) the first aim of this paper to argue that the two debates are orthogonal. Moreover, we will use Frege’s thoughts as an example of what we would contemporarily call ‘propositions’ that, though trivially Fregean, lack structure. Since it is not uncontroversial that Frege’s thoughts are unstructured, it is the second aim of this paper to show that it follows from Frege’s writings that they are. (shrink)

Frege seems to hold two incompatible theses:(i) that sentences differing in structure can yet express the same sense; and (ii) that the senses of the meaningful parts of a complex term are determinate parts of the sense of the term. Dummett offered a solution, distinguishing analysis from decomposition. The present paper offers an embellishment of Dummett?s distinction by providing a way of depicting the internal structures of complex senses?determinate structures that yield distinct decompositions. Decomposition is then shown (...) to be adequate as a foundation for the informativity and analyticity of logic. (shrink)

Frege’s use of a judgment stroke in his conceptual notation has been a matter of controversy, at least since Wittgenstein rejected it as “logically quite meaningless” in the Tractatus. Recent defenders of Frege include Tyler Burge, Nicolas Smith and Wolfgang Künne, whereas critics include William Taschek and Edward Kanterian. Against the background of these defenses and criticisms, the present paper argues that Frege faces a dilemma the two horns of which are related to his early and later (...) conceptions of asserted content respectively. On the one hand, if content is thought of as something that has propositional structure, then the judgment stroke is superfluous. On the other hand, if what is to the right of the judgment stroke is conceived as a sort of name designating a truth-value, then there is no consistent way to avoid construing the judgment stroke as a kind of predicate, and thereby fail to do justice to the act-character of judgment and assertion. (shrink)

According to Peter Aczel, the inconsistency of Frege’s system in Grundgesetze is due, not to the introduction of sets, as is usually thought, but to the introduction of the Horizontal. His argument is that the principles governing sets are intuitively correct and therefore consistent, while the scheme introducing the Horizontal amounts to an internal definition of truth conflicting with Tarski’s classic result on the undefinability of truth in the object language. The aim of this paper is to show that (...) the Horizontal is innocent: Aczel’s diagnosis is based on a mistaken view of the structure underlying Frege’s ideal language. (shrink)

This thesis is about the viability of meta-normative expressivism. On what I take to be the dominant conception of the view, it subscribes to two theses. First, that the meaning of sentences is to be explained in terms of the mental states these sentences conventionally express. Second, that there is a fundamental difference in the roles of the states expressed by normative sentences and the states expressed by descriptive sentences: descriptive sentences, according to expressivists, express mental states which are representational (...) and non-motivational, while normative sentences express non-representational and motivational states. Expressivism has attracted many naturalistically inclined philosophers for its ability to explain many of the distinctive features of normative discourse and thought, without adding entities to our ontology that are metaphysically and epistemologically problematic. In this way, expressivism promises to preserve the legitimacy of our ordinary normative practice within a naturalistic world-view, without giving up on any of its distinctive features. Despite it’s benefits, expressivism also faces significant problems. While one of these problems, the Frege-Geach Problem, has attracted a lot of attention, there are several other problems that have not been sufficiently addressed by. But, given that the reasonable assumption that the plausibility of philosophical theories needs to be assessed holistically, it seems that one should pay attention to these problems to be able to assess expressivism’s overall plausibility. In this thesis I explain how expressivists can solve two of these problems. The first problem the dissertation is concerned with is the normative attitude problem. This is a dilemma based on the challenge that expressivists need to give an account of the nature of the attitude that normative thinking consists in. The dilemma is then that expressivists could either do this by holding that normative thinking consists in sui generis attitudes, which is uninformative and potentially in conflict with naturalism, or by holding that normative thinking reduces to attitudes fully describable in non-normative terms, which is in conflict with our intuitions about normative thinking. I argue that this dilemma is structurally identical to a dilemma which meta-normative representationalism faces and that expressivists can use the same theoretical resources to address the normative attitude problem meta-normative representationalists have used to address their version of the dilemma. I also argue that these resources will not only help more traditional versions of expressivism, according to which normative thinking reduces to familiar kinds of attitudes fully describable in non-normative terms, but opens up the possibility of an expressivist view according to which normative thinking consists in sui generis attitudes. The second problem I consider is a challenge to a particular expressivist project: quasi-realism. Part of this project is to show that expressivism is compatible with a web of closely connected assumptions, namely, that normative thought and discourse are truth-apt and normative judgements are beliefs. While quasi-realists have made some progress in this direction, there is one relevant phenomenon that has so far been neglected, namely, those uses of that-clauses that are associated with propositional content. This is a problematic neglect, because that-clauses figure prominently in platitudes characterizing our ordinary notions of “truth-aptitude” and “belief ”, and so expressivists need to provide a plausible account of these uses of that-clauses which fits with their allowing that normative thought and discourse are truth-apt and normative judgements are beliefs. I address this challenge as follows: I first remove any worries that one might have that a plausible account of that-clauses that helps the quasi-realist could be given, by introducing the distinction between semantics and meta-semantics and locating expressivism at the level of metasemantics. I then develop a deflationist view of that-clauses which suits the quasi-realist’s purposes. I start by giving such a view for the use of that-clauses in meaning-attributions by expanding on the work of Wilfried Sellars. I then go on to explain how the account can be generalized to the use of that-clauses in belief-attributions and propositional attitude ascriptions more generally, in a way that allows expressivists to say that normative judgements are beliefs. (shrink)

ABSTRACT This paper reveals David Hilbert’s position in the philosophy of mathematics, circa 1900, to be a form of non-eliminative structuralism, predating his formalism. I argue that Hilbert withstands the pressing objections put to him by Frege in the course of the Frege-Hilbert controversy in virtue of this early structuralist approach. To demonstrate that this historical position deserves contemporary attention I show that Hilbertian structuralism avoids a recent wave of objections against non-eliminative structuralists to the effect that they (...) cannot distinguish between structurally identical but importantly distinct mathematical objects, such as the complex roots of $-1$. (shrink)