Frege: Logic and Philosophy of Logic

In this essay, I argue that Frege plagiarized the Stoics --and I mean exactly that-- on a large scale in his work on the philosophy of logic and language as written mainly between 1890 and his death in 1925 (much of which published posthumously) and possibly earlier. I use ‘plagiarize' (or 'plagiarise’) merely as a descriptive term. The essay is not concerned with finger pointing or casting moral judgement. The point is rather to demonstrate carefully by means of detailed evidence (...) that there are numerous (over a hundred) and extensive parallels both in formulation and --more importantly-- in content between the Stoics and Frege, parallels so plentiful that one would be hard pressed to brush them off as coincidence. These parallels include several that appear to occur in no other modern works that were published before Frege’s own and were accessible to him. Additionally, a cluster of corroborating historical data is adduced to support the suggestion, showing how easy it would have to been for Frege to plagiarize the Stoics. This (first) part of the essay is easy to read and vaguely entertaining, or so I hope. (shrink)

In this dissertation I offer a global and detailed reconstruction of the logic developed by Gottlob Frege throughout his career. Even though Frege's logic suffered profound modifications from his initial formulation in Begriffsschrift to its revised version in Grundgesetze, the significant differences between these two works have been rarely taken at face value. I not only argue that these differences exist, but I also explain how they should be understood in the light of the evolution of Frege's thought. First, I (...) suggest a new reconstruction of Begriffsschrift's logic, which amounts to a completely novel reading of its formal system—one that contradicts the core of modern historical studies. In particular, I defend that this logic is not—as it has been repeatedly said—a second-order logic and provide the following reasons. (1) The language is not properly a formal language. (2) In Begriffsschrift there is only one sort of quantification: quantification over arguments. (3) Begriffsschrift's logic does not have a semantics in the modern sense. Second, I offer an explanation of the reasons that drive the evolution of Frege's logic. The transition from Begriffsschrift to Grundgesetze has been seldom addressed and never fully explained. According to my historical analysis, the switch from Frege's position concerning logic in Begriffsschrift to his later conception—finally established in Grundgesetze—can be articulated through the adoption of the distinction between concept and object as the basic element of the formal system. This leads to a formalisation of the notion of concept, which in the end drives to Grundgesetze's notion of function. Finally, I put forward a global analysis of Grundgesetze's logic. In this work, Frege develops a formal system that resembles in many relevant ways a second-order one. I suggest a reconstruction of this formal system that allows us to compare it with Begriffsschrift's. In particular, I formulate precisely every rule of inference proposed by Frege and especially focus on the rules of substitution. Moreover, I reflect on several meta-logical results that can be drawn from this reconstruction. (shrink)

Diese Arbeit stellt Freges Denken in seiner Entwicklung von den Anfängen bis zum Auftreten des Widerspruch dar. Ausführlich behandelt sind die Begriffsschrift, die Erläuterungsschriften dazu, die Grundlagen der Arithmetik sowie die Texte im Übergang zu den Grundgesetzen der Arithmetik, ein- schließlich der klassischen Aufsätze Funktion und Begriff, Über Sinn und Bedeutung und Über Begriff und Gegenstand. Die Texte werden nach Chronologie und Stellung zueinander präzise aufgeschlüsselt; auch die zeitgenössischen Rezensionen und Freges wissenschaftliches Umfeld werden berücksichtigt. Freges Werk wird dadurch in (...) seiner beeindruckenden Zielstrebigkeit, Geschlossenheit und Tiefe sichtbar. Sein Zentrum ist die radikale Neufassung der Logik, ausgehend von der Grundunterscheidung von Begriff und Gegenstand, die zunächst eher unauffällig über die Zerfällung des Urteils in Funktion und Argument eingeführt und mit f(a) notiert wird. Zusammen mit der Einführung einer (Quantoren-)Notation, um die Allgemeinheit der Einsetzungen auf beiden Positionen einzuschränken, übertrifft Freges Logik die traditionelle, alle zeitgenössischen und etliche spätere an Präzision und Ausdruckskraft. Eben die grundsätzliche Trennung von Begriff und Gegenstand erweist sich aber für sein wissenschaftliches Hauptanliegen, die Ableitung der Arithmetik aus der Logik, als schwerwiegendes, letztlich nicht zu überwindendes Hindernis. Es gelingt ihm nicht, die Zahlen als „logische Gegenstände“ überzeugend einzuführen, und so zeigt er wider Willen die wesentliche Verschiedenheit von Logik und Arithmetik auf. (shrink)

Dieses Buch enthält in einer historisch-kritischen Edition die Texte, die es in seinem Hauptteil kommentiert: Das Vorwort (1893) zu Gottlob Freges Hauptwerk, den "Grundgesetzen der Arithmetik", in dem er seine fulminante Psychologismus-Kritik vorträgt; die drei von Frege selbst veröffentlichten "Logischen Untersuchungen" (1918-1923), in denen er "die Ernte [s]eines Lebens heimbringen" wollte; und schließlich ein Fragment aus seinem Nachlass, das der Entwurf zu einer vierten LU ist.

Gottlob Frege is the single most important figure in the development of modern mathematical logic, and is recognized as a founder of analytical philosophy. The primary aim of this work is to articulate the philosophical basis of Frege's logic and logical theory. I argue that the most general forces which animate Frege's work are neither Kantian, as is sometimes maintained, nor congenial to the semantical outlook on logic which has since Frege's time become standard. These forces are most conspicuous in (...) Frege's conception of the nature of objectivity; historically, it agrees in essential respects with pre-Kantian enlightenment Rationalism. A great deal of space is devoted to showing the influence of this philosophy on the particulars of Frege's logical theory, and to a general criticism which culminates in a comparison with Wittgenstein's Tractatus; the work concludes with an extended discussion of the nature and significance of logicism as Frege conceived it, and a diagnosis of its failure in that light. Frege is a founder of analytical philosophy, but, as I argue, his most basic commitments have rarely been properly acknowledged, and some are actually deeply inimical to analytical philosophy as currently practiced. An ulterior aim of the work is to awaken a desire for a more explicit reckoning and evaluation of the most basic presuppositions of contemporary analytical philosophy. (shrink)

This entry explains Frege's Theorem by using the modern notation of the predicate calculus. Frege's Theorem is that the Dedekind-Peano axioms for number theory are derivable from Hume's Principle, given the axioms and rules of second-order logic. Frege's methodology for defining the natural numbers and for the derivation of the Dedekind-Peano axioms are sketched in some detail.

This chapter explores Gottlob Frege's contribution to logic. Frege has been called the greatest logician since Aristotle, but he failed to gain influence on the mathematical community of his time and the depth and pioneering character of his work was acknowledged only after the collapse of his logicist program due to the Zermelo–Russell antinomy in 1902. Frege, by proving his theorem χ without recourse to Wertverläufe, exhibited an inconsistency in the traditional notion of the extension of a concept. He prompted (...) our awareness of a situation the future analyses of which will hopefully not only deepen our systematic control of the interplay of concepts and their extensions but also improve our understanding of the historical development of the notion of “extension of a concept” and its historiographical assessment. (shrink)

This chapter explores Gottlob Frege's contribution to logic. Frege has been called the greatest logician since Aristotle, but he failed to gain influence on the mathematical community of his time and the depth and pioneering character of his work was acknowledged only after the collapse of his logicist program due to the Zermelo–Russell antinomy in 1902. Frege, by proving his theorem χ without recourse to Wertverläufe, exhibited an inconsistency (or at least an incoherence) in the traditional notion of the extension (...) of a concept. He prompted our awareness of a situation the future analyses of which will hopefully not only deepen our systematic control of the interplay of concepts and their extensions but also improve our understanding of the historical development of the notion of “extension of a concept” and its historiographical assessment. (shrink)

Chapter One: Constructions. Entities, constructions, and functions When one travels from Los Angeles to New York, going, say, by way of St. Louis, Chicago, ...

In this entry, Frege's logic is introduced and described in some detail. It is shown how the Dedekind-Peano axioms for number theory can be derived from a consistent fragment of Frege's logic, with Hume's Principle replacing Basic Law V.

In Tractatus 5.132 Wittgenstein argues that inferential justification depends solely on the understanding of the premises and conclusion, and is not mediated by any further act. On this basis he argues that Frege’s and Russell’s rules of inference are “senseless” and “superfluous”. This line of argument is puzzling, since it is unclear that there could be any viable account of inference according to which no such mediation takes place. I show that Wittgenstein’s rejection of rules of inference can be motivated (...) by taking account of his holistic construal of the relation between inference and understanding. (shrink)

In this paper, I revisit Frege's theory of sense and reference in the constructive setting of the meaning explanations of type theory, extending and sharpening a program–value analysis of sense and reference proposed by Martin-Löf building on previous work of Dummett. I propose a computational identity criterion for senses and argue that it validates what I see as the most plausible interpretation of Frege's equipollence principle for both sentences and singular terms. Before doing so, I examine Frege's implementation of his (...) theory of sense and reference in the logical framework of Grundgesetze, his doctrine of truth values, and views on sameness of sense as equipollence of assertions. (shrink)

According to what was the standard view (Poincaré; Wang, etc.), although Frege endorses, and Kant denies, the claim that arithmetic is reducible to logic, there is not a substantive disagreement between them because their conceptions of logic are too different. In his “Frege, Kant, and the logic in logicism,” John MacFarlane aims to establish that Frege and Kant do share enough of a conception of logic for this to be a substantive, adjudicable dispute. MacFarlane maintains that for both Frege and (...) Kant, the fundamental defining characteristic of logic is “that it provides norms for thought as such (MacFarlane, 2002, p.57). I defend the standard view. I show that MacFarlane's argument rests on conflating the way that pure general logic is normative as a canon and as a propaedeutic, and that once these are distinguished the argument is blocked. (shrink)

Frege’s famous definition of number famously uses the concept of “extension”. Extensions, in the Fregean framework, are susceptible to bringing many difficulties, and, some say, even paradoxes. Therefore, neo-logicist programs want to avoid the problems and to replace the classical Fregean definition of number with Hume’s Principle. I argue that this move, even if it makes sense from a computational point of view, is at odds with Frege’s larger philosophical project. For Frege, I claim, extensions were an important part of (...) his philosophical program of logic-as-an-universal-language. This is why Frege places his project in line with Leibniz’ philosophical project of finding a lingua characterica universalis. (shrink)

Frege’s famous definition of number famously uses the concept of “extension”. Extensions, in the Fregean framework, are susceptible to bringing many difficulties, and, some say, even paradoxes. Therefore, neo-logicist programs want to avoid the problems and to replace the classical Fregean definition of number with Hume’s Principle. I argue that this move, even if it makes sense from a computational point of view, is at odds with Frege’s larger philosophical project. For Frege, I claim, extensions were an important part of (...) his philosophical program of logic-as-an-universal-language. This is why Frege places his project in line with Leibniz’ philosophical project of finding a lingua characterica universalis. (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 aim of this paper is to present a constructive solution to Frege's puzzle (largely limited to the mathematical context) based on type theory. Two ways in which an equality statement may be said to have cognitive significance are distinguished. One concerns the mode of presentation of the equality, the other its mode of proof. Frege's distinction between sense and reference, which emphasizes the former aspect, cannot adequately explain the cognitive significance of equality statements unless a clear identity criterion for (...) senses is provided. It is argued that providing a solution based on proofs is more satisfactory from the standpoint of constructive semantics. (shrink)

Frege ist bekannt für seinen Versuch, die Arithmetik aus der Logik herzuleiten. Doch welcher Begriff von Logik liegt diesem Projekt zugrunde? Wenn Logik die Grundlage der Arithmetik ist und die Arithmetik über Inhalte verfestigt, so muss die Logik selbst eine Wissenschaft mit eigenen Inhalten sein. Die Autorin zeigt, wie Frege logische Zeichen zu eigenständigen Begriffen aufwertet und dadurch eine inhaltliche Logikkonzeption überhaupt erst ermöglicht. In einem weiteren Schritt wird ein Kriterium vorgestellt, mit dessen Hilfe Frege logische Inhalte von den Inhalten (...) anderer Wissenschaften abgrenzt. Dabei wird jedoch deutlich, dass Frege bis in die 1890er Jahre braucht, um sich vollständig vom Kantischen Diktum zu lösen, die Logik sei nur ein negativer Probierstein der Wahrheit. Die Suche nach dem Grund, der Frege zu einer inhaltlichen Konzeption von Logik zwang, führt in die Geometriegeschichte des 19. Jahrhunderts. Vor ihrem Hintergrund werden schließlich die Anfangsparagraphen der Grundlagen der Arithmetik in einem neuen Licht interpretiert. (shrink)

Frege claims that the laws of logic are characterized by their “generality,” but it is hard to see how this could identify a special feature of those laws. I argue that we must understand this talk of generality in normative terms, but that what Frege says provides a normative demarcation of the logical laws only once we connect it with his thinking about truth and science. He means to be identifying the laws of logic as those that appear in every (...) one of the scientific systems whose construction is the ultimate aim of science, and in which all truths have a place. Though an account of logic in terms of scientific systems might seem hopelessly antiquated, I argue that it is not: a basically Fregean account of the nature of logic still looks quite promising. (shrink)

This paper challenges a standard interpretation according to which Frege’s conception of logic (early and late) is at odds with the contemporary one, because on the latter’s view logic is formal, while on Frege’s view it is not, given that logic’s subject matter is reality’s most general features. I argue that Frege – in Begriffsschrift – retained the idea that logic is formal; Frege sees logic as providing the ‘logical cement’ that ties up together the contentful concepts of specific sciences, (...) not the most general truths. Finally, I discuss how Frege conceives of the application of Begriffsschrift, and of its status as a ‘lingua characteristica’. (shrink)

In this paper I examine the question of logic’s normative status in the light of Carnap’s Principle of Tolerance. I begin by contrasting Carnap’s conception of the normativity of logic with that of his teacher, Frege. I identify two core features of Frege’s position: first, the normative force of the logical laws is grounded in their descriptive adequacy; second, norms implied by logic are constitutive for thinking as such. While Carnap breaks with Frege’s absolutism about logic and hence with the (...) notion that any system of logic should have a privileged claim to correctness, I argue that there is a sense in which Carnap’s framework-relative conception of logical norms has a constitutive role to play: though they are not constitutive for the conceptual activity for thinking, they do nevertheless set the ground rules that make certain forms of scientific inquiry possible in the first place. I conclude that Carnap’s principle of tolerance is tamer than one might have thought and that, despite remaining differences, Frege’s and Carnap’s conceptions of logic have more in common than one might have thought. (shrink)

The paper presents a historical account of the primacy of concepts in Frege's conception of logic. Moreover, it argues that Frege's priority-thesis does not imply that sentential logic is more basic than the logic of concepts in his thought.

This is an engaging, controversial, and refreshingly well-written book about Frege’s logic from the Begriffsschrift to the Grundgesetze. Danielle Macbeth explains Frege’s complicated two-dimensional logical notation more patiently, accurately, and with a greater variety of examples than I have previously seen. She does so, moreover, not merely by relating Frege’s innovations to the linear Principia Mathematica style logical symbolism that most logicians these days take for granted, but by delving into the deeper reasons why Frege choose to represent logical relations (...) in this special pictorial way. (shrink)

All contributions included in the present issue were originally presented at an ‘Author Meets Critics’ session organised by Richard Zach at the Pacific Meeting of the American Philosophical Association in San Diego in the Spring of 2014.

All contributions included in the present issue were originally presented at an ‘Author Meets Critics’ session organised by Richard Zach at the Pacific Meeting of the American Philosophical Association in San Diego in the Spring of 2014.

This two-part paper reviews a scholarly debate on an alleged tension in Frege's philosophy of logic. In Section 1 of Part I, I discuss Frege's view that logic is concerned with establishing norms for correct thinking and is therefore a normative science. In Section 2, I explore a different understanding of the role of logic that Frege seems to advance: logic is constitutive of the very possibility of thought, because it sets forth necessary conditions for thought. Hence, the tension the (...) view according to which logic is normative for thought seems to be incompatible with the idea that abiding by the laws of logic forms a precondition for thought. In Section 1 of Part II, I survey a number of interpretations of Frege's conception of logic that deal with this question. I show that they are for the most part either normative readings (emphasising the former understanding of the nature of logic) or constitutive readings (emphasising the latter). Finally, in Section 2, I adjudicate the debate and aim at reconciling the normative and the constitutive strands in Frege's conception of logic. (shrink)

This two-part paper reviews a scholarly debate on an alleged tension in Frege ’s philosophy of logic. In Section 1 of Part I, I discuss Frege ’s view that logic is concerned with establishing norms for correct thinking and is therefore a normative science. In Section 2, I explore a different understanding of the role of logic that Frege seems to advance: logic is constitutive of the very possibility of thought, because it sets forth necessary conditions for thought. Hence, the (...) tension the view according to which logic is normative for thought seems to be incompatible with the idea that abiding by the laws of logic forms a precondition for thought. In Section 1 of Part II, I survey a number of interpretations of Frege ’s conception of logic that deal with this question. I show that they are for the most part either normative readings or constitutive readings. Finally, in Section 2, I adjudicate the debate and aim at reconciling the normative and the constitutive strands in Frege ’s conception of logic. (shrink)

In Frege's Conception of Logic Patricia A. Blanchette explores the relationship between Gottlob Frege's understanding of conceptual analysis and his understanding of logic.

The concept of quantity (Größe) plays a key role in Frege's theory of real numbers. Typically enough, he refers to this theory as ?theory of quantity? (?Größenlehre?) in the second volume of his opus magnum Grundgesetze der Arithmetik (Frege 1903). In this essay, I deal, in a critical way, with Frege's treatment of the concept of quantity and his approach to analysis from the beginning of his academic career until Frege 1903. I begin with a few introductory remarks. In Section (...) 2, I first analyze Frege's use of the term ?source of knowledge? (?Erkenntnisquelle?) with particular emphasis on the logical source of knowledge. The analysis includes a brief comparison between Frege and Kant's conceptions of logic and the logical source of knowledge. In a second step, I examine Frege's theory of quantity in Rechnungsmethoden, die sich auf eine Erweiterung des Größenbegriffes gründen (Frege 1874). Section 3 contains a couple of critical observations on Frege's comments on Hankel's theory of real numbers in Die Grundlagen der Arithmetik (Frege 1884). In Section 4, I consider Frege's discussion of the concept of quantity in Frege 1903. Section 5 is devoted to Cantor's theory of irrational numbers and the critique deployed by Frege. In Section 6, I return to Frege's own constructive treatment of analysis in Frege 1903 and succinctly describe what I take to be the quintessence of his account. (shrink)

This is an engaging, controversial, and refreshingly well-written book about Frege’s logic from the Begriffsschrift to the Grundgesetze. Danielle Macbeth explains Frege’s complicated two-dimensional logical notation more patiently, accurately, and with a greater variety of examples than I have previously seen. She does so, moreover, not merely by relating Frege’s innovations to the linear Principia Mathematica style logical symbolism that most logicians these days take for granted, but by delving into the deeper reasons why Frege choose to represent logical relations (...) in this special pictorial way. (shrink)

The paper presents a historical account of the primacy of concepts in Frege's conception of logic. Moreover, it argues that Frege's priority-thesis (i.e., the assumption that judgeable contents are prior to concepts) does not imply that sentential logic is more basic than the logic of concepts in his thought.

This thesis discusses some central aspects of Wittgenstein's conception of language and logic in his Tractatus Logico-Philosophicus and brings them into relation with the philosophies of Frege and Russell. The main contention is that a fruitful way of understanding the Tractatus is to see it as responding to tensions in Frege's conception of logic and Russell's theory of judgement. In the thesis the philosophy of the Tractatus is presented as developing from these two strands of criticism and thus as the (...) culmination of the philosophy of logic and language developed in the early analytic period. Part one examines relevant features of Frege's philosophy of logic. Besides shedding light on Frege's philosophy in its own right, it aims at preparing the ground for a discussion of those aspects of the Tractatus' conception of logic which derive from Wittgenstein's critical response to Frege. Part two first presents Russell's early view on truth and judgement, before considering several variants of the multiple relation theory of judgement, devised in opposition to it. Part three discusses the development of Wittgenstein's conception of language and logic, beginning with Wittgenstein's criticism of the multiple relation theory and his early theory of sense, seen as containing the seeds of the picture theory of propositions presented in the Tractatus. I then consider the relation between Wittgenstein's pictorial conception of language and his conception of logic, arguing that Wittgenstein's understanding of sense in terms of bipolarity grounds his view of logical complexity and of the essence of logic as a whole. This view, I show, is free from the internal tensions that affect Frege's understanding of the nature of logic. (shrink)

A cluster of recent papers on Frege have urged variations on the themethat Frege’s conception of logic is in some crucial way incompatible with‘metatheoretic’ investigation. From this observation, significant consequencesfor our interpretation of Frege’s understanding of his enterprise are taken tofollow. This chapter aims to critically examine this view, and to isolate whatI take to be the core of truth in it. However, I will also argue that once wehave isolated the defensible kernel, the sense in which Frege was committedto (...) rejecting ‘metatheory’ is too narrow and uninteresting to support the con-clusions drawn from the thesis by its proponents. (shrink)