There have been and continue to be disagreements about how to consider the traditional square of opposition and the traditional inferences of obversion, conversion, contraposition and inversion from the perspective of contemporary quantificational logic. Philosophers have made many different attempts to save traditional inferences that are invalid when they involve empty classes. I survey some of these attempts and argue that the only satisfactory way of saving all the traditional inferences is to make the existential assumption that both the subject (...) and predicate classes and their complement classes are non-empty for all the propositions we admit. I briefly indicate the room for continued controversy over how properly to interpret Aristotle's statements regarding these inferences, but find some plausibility in the views of Manley Thompson and A.N.Prior that Aristotle had in mind a particular arrangement of existential import unfamiliar to most contemporary logicians. (shrink)

This paper discusses the reports in Diogenes Laertius and in Sextus Empiricus concerning the classification of propositions. It is argued that the material in Sextus uses a source going back to the Dialectical school whose most prominent members were Diodorus Cronus and Philo of Megara. The material preserved in Diogenes Laertius, on the other hand, goes back to Chrysippus.

Mathematics textbooks teach logical reasoning by example, a practice started by Euclid; while logic textbooks treat logic as a subject in its own right without practical application to mathematics. Stuck in the middle are students seeking mathematical proficiency and educators seeking to provide it. To assist them, the article explains in practical detail how to teach logic-based skills such as: making mathematical reasoning fully explicit; moving from step to step in a mathematical proof in logically correct ways; and checking to (...) make sure inferences are logically correct. The methodology can easily be extended beyond the four examples analyzed. (shrink)

Neste artigo é defendida a tese de que a noção aristotélica de perfeição silogística não é completamente arbitrária e reflete características lógicas, apesar de alguns aspectos não lógicos. Em consonância com a sugestão de alguns intérpretes de que a validade dos silogismos em primeira figura se fundamenta no dictum de omni et nullo, será apontado como essa fundamentação se desdobra em procedimentos dedutivos encontrados nos textos de Aristóteles. Tomando definições ou explicitações das proposições categóricas como parâmetro, a perfeição ou imperfeição (...) de um silogismo, independentemente das relações de prova que se adote entre as figuras silogísticas, não se mostra arbitrária. (shrink)

Today there appears to be a widespread impression that W. V. Quine's notorious critique of modal logic, based on certain ideas about reference, has been successfully answered. As one writer put it some years ago: “His objections have been dead for a while, even though they have not yet been completely buried.” What is supposed to have killed off the critique? Some would cite the development of a new ‘possible-worlds’ model theory for modal logics in the 1960s; others, the development (...) of new ‘direct’ theories of reference for names in the 1970s.These developments do suggest that Quine's unfriendliness towards any formal logics but the classical and indifference towards theories of reference for any singular terms but variables were unfortunate. (shrink)

This paper is about the meaning and function of identity statements involving proper names. There are two prominent views on this topic, according to which identity statements ascribe a relation: the object-view, on which identity statements ascribe a relation borne by all objects to themselves, and the name-view, on which an identity statement 'a is b' says that the names 'a' and 'b' codesignate. The object- and name-views may seem to exhaust the field. I make a case for treating identity (...) statements as sui generis instead of attempting to explain them by means of the idea that they ascribe a relation. My contention is that once we do this, no analysis is required. -/- I do not wish to insist that we stop saying that identity statements ascribe a relation. The point is that there is a fundamental disanalogy between identity statements and other two-termed statements which we overlook to our peril. This will be seen to parallel the more recognized disanalogy between existence statements and other one-termed statements. One way of registering the fundamental disanalogy is to say that identity statements are not relational, but this is not essential. Following my negative arguments in section 2, I employ some simple diagrammatical models in section 3 to exhibit the fundamental disanalogy. In a final section I respond to some possible objections which may be raised against this kind of approach. (shrink)

Aristotle's General Definition of the Syllogism may be taken as consisting of two parts: the Inferential Conditions and the Final Clause. Although this distinction is well known, traditional interpretations neglect the Final Clause and its influence on syllogistic. Instead, the aforementioned tradition focuses on the Inferential Conditions only. We intend to show that this neglect has severe consequences not just on syllogistic but on the whole exegesis of Aristotle's Prior Analytics I. Due to these consequences, our objective is to analyse (...) the General Definition's Final Clause and its consequences on syllogistic. We propose a reading of the Final Clause as an additional criterion for distinguishing some arguments as properly syllogistic ones and as a main theme which connects all parts of the Prior Analytics I into one coherent piece of work. (shrink)

No tratado intitulado Segundos Analíticos, Aristóteles desenvolve uma teoria da demonstração científica e da ciência demonstrativa. Ali, o conhecimento científico é descrito pelo filósofo como envolvendo uma certa "necessidade". Alguns intérpretes associam esta noção de necessidade à necessidade modal, pertinente à silogística modal de Aristóteles. Esta interpretação, todavia, tornaria o modelo de ciência proposto nos Analíticos incompatível com os explananda das ciências da natureza, cuja cientificidade o próprio Aristóteles reiteradamente defendeu. A fim de evitar este inconveniente, abordamos e reconstruímos a (...) mencionada interpretação, reconhecemos suas falhas e propomos, seguindo outra tendência da literatura secundária, uma leitura alternativa da noção de necessidade como adequação explanatória, a qual garantiria a cientificidade dos fenômenos naturais. (shrink)

This paper presents a new theory of modal reasoning, i.e. reasoning about what may or may not be the case, and what must or must not be the case. It postulates that individuals construct models of the premises in which they make explicit only what is true. A conclusion is possible if it holds in at least one model, whereas it is necessary if it holds in all the models. The theory makes three predictions, which are corroborated experimentally. First, conclusions (...) correspond to the true, but not the false, components of possibilities. Second, there is a key interaction: it is easier to infer that a situation is possible as opposed to impossible, whereas it is easier to infer that a situation is not necessary as opposed to necessary. Third, individuals make systematic errors of omission and of commission. We contrast the theory with theories based on formal rules. (shrink)

This paper seeks to elucidate the distinctive nature of the rational impression on its own terms, asking precisely what it means for the Stoics to define logikē phantasia as an impression whose content is expressible in language. I argue first that impression, generically, is direct and reflexive awareness of the world, the way animals get information about their surroundings. Then, that the rational impression, specifically, is inherently conceptual, inferential, and linguistic, i.e. thick with propositional content, the way humans receive incoming (...) information from the world. When we suspend certain contemporary assumptions about propositional content, the textual evidence can be taken at face value to reveal why, for the Stoics, rational impressions are called thoughts (noēseis) and how the Stoics’ novel semantic entities called lekta (roughly, the meanings of our words) depend on rational impressions for their subsistence. (shrink)

This is the most comprehensive book ever published on philosophical methodology. A team of thirty-eight of the world's leading philosophers present original essays on various aspects of how philosophy should be and is done. The first part is devoted to broad traditions and approaches to philosophical methodology. The entries in the second part address topics in philosophical methodology, such as intuitions, conceptual analysis, and transcendental arguments. The third part of the book is devoted to essays about the interconnections between philosophy (...) and neighbouring fields, including those of mathematics, psychology, literature and film, and neuroscience. (shrink)

Although studies have yielded a detailed taxonomy of types of slippery slope arguments, they have failed to identify a basic argumentation scheme that applies to all. Therefore, there is no way of telling whether a given argument is a slippery slope argument or not. This paper solves the problem by providing a basic argumentation scheme. The scheme is shown to fit a clear and easily comprehensible example of a slippery slope argument that strongly appears to be reasonable, something that has (...) also been lacking. (shrink)

Commentators have not said much regarding Berkeley and Stoicism. Even when they do, they generally limit their remarks to Berkeley’s Siris (1744) where he invokes characteristically Stoic themes about the World Soul, “seminal reasons,” and the animating fire of the universe. The Stoic heritage of other Berkeleian doctrines (e.g., about mind or the semiotic character of nature) is seldom recognized, and when it is, little is made of it in explaining his other doctrines (e.g., immaterialism). None of this is surprising, (...) considering how Stoics are considered arch-materialists and determinists. My aim is to suggest that our understanding of Berkeley’s philosophy is improved significantly by acknowledging its underlying Stoic character. I argue that Berkeley proposes not only a semantic ontology based on assumptions of Stoic logic but also a doctrine in which perceptions or ideas are intelligible precisely because they are always embedded in the propositions of a discourse or language. (shrink)

Although most scholars trace the Liar Paradox to Plato’s contemporary, Eubulides, the paper argues that Plato builds something very like the Liar Paradox into the very structure of his dialogues with significant consequences for understanding his views. After a preliminary exposition of the liar paradox it is argued that Plato builds this paradox into the formulation of many of his central doctrines, including the “Divided Line” and the “Allegory of the Cave” and the “Ladder of Love”. Thus, Plato may have (...) been the first to formulate the view that Graham Priest calls dialetheism, roughly, the view that some contradictions are, in an illuminating way, inescapable and true. The paper argues that Plato builds this Liar paradox into the formulation of his signature views because he holds that the attempt by finite human beings to theorize about transcendent realities results in the simultaneous necessity, and impossibility, of transgressing the limits of language—leading to the paradoxes. Finally, it is argued that the existence of these paradoxes in these Platonic doctrines is the direct result of an intrinsic hermeneutical circle in Plato’s aforementioned signature views. (shrink)

Aristotle studies syllogistic argumentation in Sophistical Refutations and Prior Analytics. In the latter he focuses on the formal and syntactic character of arguments and treats the sullogismoi and non-sullogismoi as argument patterns with valid or invalid instances. In the former Aristotle focuses on semantics and rhetoric to study apparent sullogismoi as object language arguments. Interpreters usually take Sophistical Refutations as considerably less mature than Prior Analytics. Our interpretation holds that the two works are more of a piece than previously believed (...) and, indeed, that Aristotle's treatment of fallacious reasoning presupposes the results of the formal theory. (shrink)

Today it would be considered "bad Platonic metaphysics" to think that among all the concrete instances of a property there could be a universal instance so that all instances had the property by virtue of participating in that concrete universal. Yet there is a mathematical theory, category theory, dating from the mid-20th century that shows how to precisely model concrete universals within the "Platonic Heaven" of mathematics. This paper, written for the philosophical logician, develops this category-theoretic treatment of concrete universals (...) along with a new concept to abstractly model the functions of a brain. (shrink)

A dialectical contradiction can be appropriately described within the framework of classical formal logic. It is in harmony with the law of noncontradiction. According to our definition, two theories make up a dialectical contradiction if each of them is consistent and their union is inconsistent. It can happen that each of these two theories has an intended model. Plenty of examples are to be found in the history of science.

I characterize the deductivist ideal of justification and, following to a great extent Toulmin’s work The Uses of Argument, I try to explain why this ideal is erroneous. Then I offer an alternative model of justification capable of making our claims to knowledge about substantial matters sound and reasonable. This model of justification will be based on a conception of justification as the result of good argumentation, and on a model of argumentation which is a pragmatic linguistic reconstruction of Toulmin’s (...) model of argument. (shrink)

In the Critique of Pure Reason, Kant conceives of general logic as a set of universal and necessary rules for the possibility of thought, or as a set of minimal necessary conditions for ascribing rationality to an agent . Such a conception, of course, contrasts with contemporary notions of formal, mathematical or symbolic logic. Yet, in so far as Kant seeks to identify those conditions that must hold for the possibility of thought in general, such conditions must hold a fortiori (...) for any specific model of thought, including axiomatic treatments of logic and standard natural deduction models of first-order predicate logic. Kant's general logic seeks to isolate those conditions by thinking through – or better, reflecting on – those conditions that themselves make thought possible. (shrink)

Discrete supposition occurs whenever a discrete term, such as ‘Socrates‘, is the subject of a given proposition. I propose to examine this apparently simple notion. I shall draw attention to the incongruity, within a general theory of the semantic variation of terms in a propositional context, of the notion of discrete supposition, in which a term usually has a single semantic correlate. The incongruity comes to the fore in those treatises that attempt to describe discrete supposition as a sort of (...) personal supposition, although the same term cannot be in simple supposition in another propositional context, because it has no significate distinct from its suppositum. This shows a fundamental link between common signification, simple supposition and predicability, three notions that rely on the existence of a significate distinct and independent from the suppositum of the term. The connection is to be seen especially in William of Sherwood’s Introductiones, the only author of a terminist Summa who recognizes the existence of simple supposition for discrete terms. (shrink)

Used informally, the Reductio ad Absurdum (RAA) consists in reasoning appealing to the logically implied, absurd consequences of a hypothetical proposition, in order to refute it. This kind of reasoning resembles the Argument from Consequences, which appeals to causally induced consequences. These types of argument are sometimes confused, since it is not worked out how these different kinds of consequences should be distinguished. In this article it is argued that the logical consequences in RAA-argumentation can take different appearances and that (...) it therefore must be concluded that RAA cannot be characterised by a specific content, but must instead be characterised as an argument form. Furthermore, clues are provided to distinguish RAA reasoning from the Argument from Consequences. (shrink)

A famous essay by Wigner is reexamined in view of more recent developments around its topic, together with some remarks on the metaphysical character of its main question about mathematics and natural sciences.

The wider topic to which the content of this paper belongs is that of the relationship between formal logic and real argumentation. Of particular potential interest in this connection are held to be substantive arguments constructed by philosophers reputed equally as authorities in logical theory. A number of characteristics are tentatively indicated by the author as likely to be encountered in such arguments. The discussion centers afterwards, by way of specification, on a remarkable piece of argument quoted in Cicero’s dialog (...) On Divination and ascribed to Stoic thinkers. The Stoics’ formal theory of inference is summarily referred to in this context, with special emphasis on their basic deductive schemata (‘indemonstrables’), some of them recognizable as links in the overall structure of the quoted argument. The main lines of Cicero’s criticism of the Stoic argument are next commented upon, with emphasis on his implied view as to the requirements of a good argument. Towards the end of the paper, a few considerations are added on the changes in the prevailing style of argumentation conspicuous in the three famous Roman Stoics. (shrink)

This essay discusses Peirce’s appeal to logical machines as an argument against psychologism. It also contends that some of Peirce’s anti-psychologistic remarks on logic contain interesting premonitions arising from his perception of the asymmetry of proof complexity in monadic and relational logical calculi that were only given full formulation and explication in the early twentieth century through Church’s Theorem and Hilbert’s broad-ranging Entscheidungsproblem.

If the healthy and the pathological are not merely judgments qualifiers, but real phenomena, it must be possible to define both of them positively, which, in this context, means as factual contraries. On the other hand, only a privative definition, either of the pathological as 'non-healthy', or of the healthy as 'non-pathological', can rationally circumscribe all possible states of an organism. This fluctuation between two meanings of the 'healthy'-'pathological' opposition, factual vs. rational, characterizes the ordinary usage of these concepts and (...) puts all philosophical definitions in a hopeless situation. Although a scientific definition may conceal this equivocation by adequately setting out the terms of the problem of discriminating between the 'healthy' and the 'pathological', it could explain some of the difficulties met in determining 'gold standards', in the choice of separators, and in the assessment of the diagnostic qualities of tests. (shrink)

I argue that Beall and Restall's logical pluralism fails. Beall–Restall pluralism is the claim that there are different, equally correct logical consequence relations in a single language. Their position fails for two, related, reasons: first, it relies on an unmotivated conception of the ‘settled core’ of consequence: they believe that truth-preservation, necessity, formality and normativity are ‘settled’ features of logical consequence and that any relation satisfying these criteria is a logical consequence relation. I consider historical evidence and argue that their (...) position relies on an unmotivated conception of the settled features of logical consequence. There are many features that are just as settled but which are inconsistent with pluralism. Second, I argue that Beall–Restall pluralism fails to hold in a single language with a single selection of logical constants, which they require for the position to be distinct from Carnap's. I consider various ways in which Beall and Restall can resist this meaning variance, particularly for negation, but argue that the strongest way relies on an unmotivated conception of the settled features of the logical constants. (shrink)

Many historians of analytic philosophy consider the early philosophy of Moore, Russell and Wittgenstein as much more neo-Hegelian as once believed. At the same time, the authors who closely investigate Green, Bradley and Bosanquet find out that these have little in common with Hegel. The thesis advanced in this chapter is that what the British (ill-named) neo-Hegelians brought to the early analytic philosophers were, above all, some ideas of Lotze, not of Hegel. This is true regarding: (i) Lotze’s logical approach (...) to practically all philosophical problems; (ii) his treating of the concepts relation, structure (constructions) and order; (iii) the discussion of the concepts of states of affairs, multiple theory of judgment, general logical form; (iv) some common themes like panpsychism and contemplating the world sub specie aeternitatis. (shrink)

Abstract. As a general theory of reasoning—and as a general theory of what holds true under every possible circumstance—logic is supposed to be ontologically neutral. It ought to have nothing to do with questions concerning what there is, or whether there is anything at all. It is for this reason that traditional Aristotelian logic, with its tacit existential presuppositions, was eventually deemed inadequate as a canon of pure logic. And it is for this reason that modern quantification theory, too, with (...) its residue of existentially loaded theorems and patterns of inference, has been claimed to suffer from a defect of logical purity. The law of non-contradiction rules out certain circumstances as impossible—circumstances in which a statement is both true and false, or perhaps circumstances where something both is and is not the case. Is this to be regarded as a further ontological bias? (shrink)

This paper examines the contemporary philosophical and cognitive relevance of Charles Peirce's diagrammatic logic of existential graphs (EGs), the ‘moving pictures of thought’. The first part brings to the fore some hitherto unknown details about the reception of EGs in the early 1900s that took place amidst the emergence of modern conceptions of symbolic logic. In the second part, philosophical aspects of EGs and their contributions to contemporary logical theory are pointed out, including the relationship between iconic logic and images, (...) the problem of the meaning of logical constants, the cognitive economy of iconic logic, the failure of the Frege–Russell thesis, and the failure of the Language of Thought hypothesis. (shrink)

Frege begins his exposition of the symbol system employed in his Begriffsschrift by introducing the sign ⟝, whereby, he says, “[a] judgment is always to be expressed”.[The judgment sign] stands to the left of the sign or complex of signs in which the content of the judgment is given. If we omit the little stroke at the left of the horizontal stroke, then the judgment is to be transformed into a mere complex of ideas; the author is not expressing his (...) recognition or nonrecognition of the truth of this. (shrink)

History and Philosophy of Logic, Volume 32, Issue 2, Page 191-193, May 2011.

A general survey of Frege's views on truth, the paper explores the problems in response to which Frege's distinctive view that sentences refer to truth-values develops. It also discusses his view that truth-values are objects and the so-called regress argument for the indefinability of truth. Finally, we consider, very briefly, the question whether Frege was a deflationist.

Toisaalta ennennäkemätön äärettömien joukko-opillisten menetelmien hyödyntäminen sekä toisaalta epäilyt niiden hyväksyttävyydestä ja halu oikeuttaa niiden käyttö ovat ratkaisevasti muovanneet vuosisatamme matematiikkaa ja logiikkaa. Tämän kehityksen vaikutus nykyajan filosofiaan on myös ollut valtaisa; merkittävää osaa siitä ei voi edes ymmärtää tuntematta sen yhteyttä tähän matematiikan ja logiikan vallankumoukseen. Lähestymistapoja, jotka tavalla tai toisella hyväksyvät äärettömän matematiikan ja perinteisten logiikan sääntöjen (erityisesti kolmannen poissuljetun lain) soveltamisen myös sen piirissä, on tullut tavaksi kutsua klassiseksi matematiikaksi ja logiikaksi erotuksena nämä hylkäävistä radikaaleista intuitionistisista ja (...) konstruktivistisista opeista. (shrink)

The problem of enumerating the types of Boolean functions under the group of variable permutations and complementations was first stated by Jevons in the 1870s. but not solved in a satisfactory way until the work of Pólya in 1940. This paper explains the details of Pólya's solution, and also the history of the problem from the 1870s to the 1970s.

The taxonomy and analysis of fallacies in Aristotle's Sophistical Refutations pre-date the formal logic of his Prior Analytics A4-6. Of the 64 fully described examples of ?sophistical refutations? which are fallacious because they are only apparently valid, 49 have the wrong number of premisses or the wrong form of premiss or conclusion for analysis by the Prior Analytics theory of the categorical syllogism. The rest Aristotle either frames so that they do not look like categorical syllogisms or analyses in a (...) quite different way than by categorical syllogistic. (shrink)

This paper considers the question of whether Mill's account of the nature and justificatory foundations of deductive logic is psychologistic. Logical psychologism asserts the dependency of logic on psychology. Frequently, this dependency arises as a result of a metaphysical thesis asserting the psychological nature of the subject matter of logic. A study of Mill's System of Logic and his Examination reveals that Mill held an equivocal view of the subject matter of logic, sometimes treating it as a set of psychological (...) processes and at other times as the objects of those processes. The consequences of each of these views upon the justificatory foundations of logic are explored. The paper concludes that, despite his providing logic with a prescriptive function, and despite his avoidance of conceptualism, Mill's theory fails to provide deductive logic with a justificatory foundation that is independent of psychology. (shrink)

Charles S. Peirce frequently mentioned reading Richard Whately's Elements of Logic when he was 12 years old. Throughout his life, Peirce emphasized the importance of that experience. This valorization of Whately is puzzling at first. Early in his career Peirce rejected Whately's central logical doctrines. What valuable insight concerning logic was robust enough to survive these specific rejections? Peirce recommended a biographical approach to understanding his philosophy. This essay follows that suggestion by considering Peirce's reading of Whately in a larger (...) life context. Surprisingly many factors in Charles Peirce's personal and intellectual development were at play when he read Whately. His father, Benjamin Peirce, oversaw rigorous home schooling intended to train young Charley for a brilliant intellectual career. Laboratory experience with qualitative chemical analysis exposed the boy to the logic of scientific investigation, specifically to the hypothetico-deductive method of inquiry. However, tensions between father and son developed over Charles' wish to devote his life to studying the logic of science. The two also disagreed upon the value of formal science. Against this background we will review relevant logical doctrines of Whately's book, as well as his innovative formalizing practice of logical inquiry. Then we will see that it was Whately's lessons about formal science that were of such importance to Peirce. (shrink)

Modern logicians have sought to unlock the modal secrets of Aristotle's Syllogistic by assuming a version of essentialism and treating it as a primitive within the semantics. These attempts ultimately distort Aristotle's ontology. None of these approaches make full use of tests found throughout Aristotle's corpus and ancient Greek philosophy. I base a system on Aristotle's tests for things that can never combine (polarity) and things that can never separate (inseparability). The resulting system not only reproduces Aristotle's recorded results for (...) the apodictic syllogistic in the Prior Analytics but it also generates rather than assumes Aristotle's distinctions among 'necessary', 'essential' and 'accidental'. By developing a system around tests that are in Aristotle and basic to ancient Greek philosophy, the system is linked to a history of practices, providing a platform for future work on the origins of logic. (shrink)

Sections 1 through 3 present all of the main ideas behind the probabilistic logic of evidential support. For most readers these three sections will suffice to provide an adequate understanding of the subject. Those readers who want to know more about how the logic applies when the implications of hypotheses about evidence claims (called likelihoods) are vague or imprecise may, after reading sections 1-3, skip to section 6. Sections 4 and 5 are for the more advanced reader who wants a (...) detailed understanding of some telling results about how this logic may bring about convergence to the truth. (shrink)

The ‘Dialectical school’ denotes a group of early Hellenistic philosophers that were loosely connected by philosophizing in the — Socratic — tradition of Eubulides of Megara and by their interest in logical paradoxes, propositional logic and dialectical expertise. . Its two best known members, Diodorus Cronus and Philo the Logician, made groundbreaking contributions to the development of theories of conditionals and modal logic. Philo introduced a version of material implication; Diodorus devised a forerunner of strict implication. Each developed a system (...) of modal notions that satisfies the basic logical requirements laid down by modern standard modal theories. In antiquity, Diodorus Cronus was famous for his so called Master Argument, which aims to prove that only the actual is possible. (shrink)

Conventional approaches to consciousness assume that our current science tells us within tolerable limits what physical nature is. Because nature so understood cannot explain consciousness as we seem to experience it ourselves, explaining consciousness becomes a problem. One solution is to rethink what consciousness is so that it becomes the sort of thing our current natural science could in principle explain. Whitehead takes the opposite approach, using the existence of consciousness as a clue to what nature must be if it (...) can generate something like consciousness. The justification for this approach can be found in Whitehead’s implicit indictment of descriptive phenomenology. According to Whitehead, the seemingly insoluble problem of explaining consciousness naturalistically is an artifact created by the assumption that consciousness faithfully samples the world, when in fact it obscures the very aspects of nature that are indispensable to understanding how anything, including consciousness itself, could emerge through a physical process. (shrink)

1. 1. PROGRAM It will be our aim to reconstruct, with precision, certain views which have been traditionally associated with nominalism and to investigate problems arising from these views in the construction of interpreted formal systems. Several such systems are developed in accordance with the demand that the sentences of a system which is acceptable to a nominalist must not imply the existence of any entities other than individuals. Emphasis will be placed on the constructionist method of philosophical analysis. To (...) follow this method is to introduce the central notions of the subject-matter to be investigated into a system governed by exact rules. For example, the constructionist method of investigating the properties of geometric figures may consist in formulating a system of postulates and definitions which, together with the apparatus of formal logic, generates all necessary truths concerning geometric figures. Similarly, a constructionist analysis of the notion of an individual may take the form of an axiomatic theory whose provable assertions are just those which seem essential to the role played by the concept of an individual in system atic contexts. Such axiomatic theories gain in interest if they are supple mented by precise semantical rules specifying the denotation of all terms and the truth conditions of all sentences of the theory. (shrink)

The period from 1900 to 1935 was particularly fruitful and important for the development of logic and logical metatheory. This survey is organized along eight "itineraries" concentrating on historically and conceptually linked strands in this development. Itinerary I deals with the evolution of conceptions of axiomatics. Itinerary II centers on the logical work of Bertrand Russell. Itinerary III presents the development of set theory from Zermelo onward. Itinerary IV discusses the contributions of the algebra of logic tradition, in particular, Löwenheim (...) and Skolem. Itinerary V surveys the work in logic connected to the Hilbert school, and itinerary V deals specifically with consistency proofs and metamathematics, including the incompleteness theorems. Itinerary VII traces the development of intuitionistic and many-valued logics. Itinerary VIII surveys the development of semantical notions from the early work on axiomatics up to Tarski's work on truth. (shrink)