Strenge Beweise und das Verbot der metábasis eis állo génos

In his booklet ‘Contributions to a better founded presentation of mathematics’ of 1810 Bernard Bolzano made his first serious attempt to explain the notion of a rigorous proof. Although the system of logic he employed at that stage is in various respects far below the level of the achievements in his later Wissenschaftslehre, there is a striking continuity between his earlier and later work as regards the methodological constraints on rigorous proofs. This paper tries to give a perspicuous and critical account of the fragmentary logic of Beyträge, and it shows that there is a tension between that logic and Bolzano's methodological ban on ‘kind crossing’.     

The Evolution of Principia Mathematica; Bertrand Russell's Manuscripts and Notes for the Second Edition

This paper deals with Popper's little-known work on deductive logic, published between 1947 and 1949. According to his theory of deductive inference, the meaning of logical signs is determined by certain rules derived from ‘inferential definitions’ of those signs. Although strong arguments have been presented against Popper's claims (e.g. by Curry, Kleene, Lejewski and McKinsey), his theory can be reconstructed when it is viewed primarily as an attempt to demarcate logical from non-logical constants rather than as a semantic foundation for logic. A criterion of logicality is obtained which is based on conjunction, implication and universal quantification as fundamental logical operations.     

The Arabico-Islamic background of Al-Fārābī's logic

This paper examines al-Fārābī's logical thought within its Arabico-Islamic historical background and attempts to conceptualize what this background contributes to his logic. After a brief exposition of al-Fārābī's main problems and goals, I shall attempt to reformulate the formal structure of Arabic linguistics (AL) in terms of the ontological and formal characteristics that Arabic logic is built upon. Having discussed the competence of al-Fārābī in the history of AL, I will further propose three interrelated theses about al-Fārābī's logic, in terms of which I will attempt to redefine it: the logico-linguistic conception, the project of logicization, and nuclear logic. The final question that will arise is how Aristotle's logic could be built upon AL, which has a nature contrary to logic. The present paper also contributes to examining our traditional research habits in Arabic studies.     

Heidegger: The Role of Logic in his Thought

Since his inaugural lecture at Freiburg in 1929 in which Heidegger delivered his most celebrated salvo against logic, he has frequently been portrayed as an anti-logician, a classic example of the obscurity resultant upon a rejection of the discipline of logic, a champion of the irrational, and a variety of similar things. Because many of Heidegger's statements on logic are polemical in tone, there has been no little misundersanding of his position in regard to logic, and a great deal of distortion of it. All too frequently the position which is attacked as Heidegger's is a barely recognizable caricature of it. We shall, therefore, attempt to determine precisely what Heidegger understands by logic. When he “attacks” logic, as he did in the inaugural lecture, as well as in many other of his writings, what “logic” is he attacking? The word “logic” is, after all, placed in quotation marks which would seem to indicate some special sense. This paper will argue that if one takes logic as it has traditionally been understood and practiced that one is forced to the conclusion that it is incompatible with Heidegger's “way of thought” (Denkweg). This rejection of logic, however, does not deliver him up to irrationalism or the enthronement of blind instinct in place of reason, as some of his critics have charged. Neither is it a self-indulgent refusal to achieve clarity and precision which ends in a kind of mystical pseudo-poetry. Rather, it will be argued, it represents a quite valid, and indeed rich, approach to Being, though certainly not a “logical” one in the traditional sense.     

‘Necessity’ and ‘provability’ in the later wittgenstein

I present a new interpretation of Wittgenstein's later philosophy of logic and mathematics. This interpretation, like others, emphasizes Wittgenstein's attempt to reconcile platonistic and constructivistic approaches. But, unlike other interpretations, mine explains that attempt in terms of Wittgenstein's position about the relations between our concepts of necessity and provability. If what I say here is correct, then we can rescue Wittgenstein from the charge of naive relativism. For his relativism extends only to provability, and not to necessity.     

Aristotle's Prior Analytics and Boole's Laws of Thought

Prior Analytics by the Greek philosopher Aristotle (384?–?322 BCE) and Laws of Thought by the English mathematician George Boole (1815?–?1864) are the two most important surviving original logical works from before the advent of modern logic. This article has a single goal: to compare Aristotle's system with the system that Boole constructed over twenty-two centuries later intending to extend and perfect what Aristotle had started. This comparison merits an article itself. Accordingly, this article does not discuss many other historically and philosophically important aspects of Boole's book, e.g. his confused attempt to apply differential calculus to logic, his misguided effort to make his system of ‘class logic’ serve as a kind of ‘truth-functional logic’, his now almost forgotten foray into probability theory, or his blindness to the fact that a truth-functional combination of equations that follows from a given truth-functional combination of equations need not follow truth-functionally. One of the main conclusions is that Boole's contribution widened logic and changed its nature to such an extent that he fully deserves to share with Aristotle the status of being a founding figure in logic. By setting forth in clear and systematic fashion the basic methods for establishing validity and for establishing invalidity, Aristotle became the founder of logic as formal epistemology. By making the first unmistakable steps toward opening logic to the study of ‘laws of thought’—tautologies and laws such as excluded middle and non-contradiction—Boole became the founder of logic as formal ontology.

… using mathematical methods … has led to more knowledge about logic in one century than had been obtained from the death of Aristotle up to … when Boole's masterpiece was published.     

Hegel,modal logic,and the social nature of mind

ABSTRACT

Hegel's Phenomenology of Spirit provides a fascinating picture of individual minds caught up in “recognitive” relations so as to constitute a realm—“spirit”—which, while necessarily embedded in nature, is not reducible to it. In this essay I suggest a contemporary path for developing Hegel's suggestive ideas in a way that broadly conforms to the demands of his own system, such that one moves from logic to a philosophy of mind. Hence I draw on Hegel's “subjective logic”, understood in the light of modern modal logic, in an attempt to model the way minds might be thought as connected by way of shared intentional contents. Here, we should not be surprised at some of the parallels that emerge between the approaches of Hegel and the modal logician Arthur Prior, as Prior had testified to the influence of his teacher, John N. Findlay, who himself had strong Hegelian leanings. In the final section, Robert Stalnaker's version of possible-world semantics is suggested as a framework within which Hegel's recognitive account of the mind might be understood.     

A comment on mill's argument for utilitarianism

This article contains criticisms of various interpretations of Mill's argument for Utilitarianism. An attempt is made to explain how Mill conceived the rationality of his proof, and how his justification of the Principle of Utility differs from a justification of fundamental moral principles on the basis of the logic of ethical discourse.     

Dialektik Und Formalisierung

Dialectics and Formalization. In an appendix to his article Can the concept of dialectic be made clear? (JGPS 27: 131–165) the author critically examined an attempt by D. Wandschneider of reconstructing Hegelian dialectical logic by displaying antinomic structures. The main steps of this reconstruction were formalized within the framework of second order predicate logic. In his reply (JGPS 27: 347–352) Wandschneider argues that formalization is the wrong way of interpreting and judging his reconstruction project on the ground that the understanding of predication is already presupposed by predicate logic and, therefore, cannot be formalized. In the present contribution it is shown that Wandschneider's criticism is based on a fundamentally mistaken conception of formalization and formal logic and that the problems posed by his project remain completely unresolved.     

Functions in Frege,Bolzano and Husserl

This explorative article is organized around a set of questions concerning the concept of a function. First, a summary of certain general facts about functions that are a common coin in contemporary logic is given. Then Frege's attempt at clarifying the nature of functions in his famous paper Function and Concept and in his Grundgesetze is discussed along with some questions which Freges' approach gave rise to in the literature. Finally, some characteristic uses of functional notions to be found in the work of Bernard Bolzano and in Edmund Husserl's early work are presented and elucidated.     

Popper's world 3 & human creativity

This paper aims to analyse Karl Popper's conception of ‘three worlds’, and especially the problem of world 3—the world of objective knowledge. Firstly, I try to explain Popper's turn to ontological questions which I link to his antipsychologism and to issues raised by the development of logic after World War II. I then consider Popper's concept of the autonomy of world 3 and his attempt to introduce world 3 as a world of knowledge without a knowing subject. I conclude that Popper did not succeed in unifying his central idea of autonomy of knowledge with the requirement of the creative role of the critical subject carrying out the evolution of knowledge. I see the core of this contradiction especially in his co‐existing ideas of the timeless existence of world 3 and the elimination of the subject from it. The attempt to desubjectivize the realm of objective knowledge leads to a philosophically unbalanced standpoint which presupposes a creative subject and at the same time neglects it. Finally, I question Popper's account of the growth of world 3. Popper considers only cognitive motivations, and excludes a broad range of motivating factors which originate in the problems which we face in our lives, and affect our cognitive interests in world 3.     

I. Frege's ‘Kernsätze zur Logik’

The short fragment of Frege's Nachlass which bears the above title, given to it by the editors, is in fact a sequence of connected comments by him on the Introduction to Lotze's Logik, or, more exactly, a response by him to that Introduction. It is thus very probably the earliest piece of writing from Frege's pen on the philosophy of logic surviving to us, and, when it is read in this light, the motivation for its author's puzzling selection of remarks and the turns of phrase he employs become intelligible. We see here an early attempt by Frege to attain clarity about a topic that was to preoccupy him throughout his entire philosophical career, the nature of thoughts.     

‘Everybody makes errors’: The intersection of De Morgan's Logic and Probability, 1837 – 1847

For Ivor Grattan-Guinness on the occasion of his retirement. The work of Augustus De Morgan on symbolic logic in the mid-nineteenth century is familiar to historians of logic and mathematics alike. What is less well known is his work on probability and, more specifically, the use of probabilistic ideas and methods in his logic. The majority of De Morgan's work on probability was undertaken around 1837?–?1838, with his earliest publications on logic appearing from 1839, a period which culminated with the publication of his Formal Logic in 1847. This article examines the overlap between his work on probability theory and logic during the earliest period of his interest in both.     

A darkly bright republic: Milton's poetic logic

My first section considers Walter J. Ong's influential analyses of the logical method of Peter Ramus, on whose system Milton based his Art of Logic. The upshot of Ong's work is that philosophical logic has become a kind monarch over all other discourses, the allegedly timeless and universal method of mapping and diagramming all concepts. To show how Milton nevertheless resists this tyrannical result in his non-Logic writings, my second section offers new readings of Milton's poems Il Penseroso and Sonnet 16: “On His Blindness”, along with his prose epilogue to his elegies (and thereby the entire collection entitled Poems). These readings attempt to show (1) the original admixing of philosophy and poetry (under the heading of “thoughtfulness”), (2) the shadow-hidden superiority of poetry in connection to the effeminising disability of blindness, and (3) the potential irony of an apology that arguably suggests poetry's superiority to philosophy. Finally, I rest my case for Milton's rebellion by offering an interpretation of Paradise Lost which affirms the character of Satan qua dark, queer, poetic figure of classical republicanism.     

Logical Foundations and Kant's Principles of Formal Logic

The abstract status of Kant's account of his ‘general logic’ is explained in comparison with Gödel's general definition of a formal logical system and reflections on ‘abstract’ (‘absolute’) concepts. Thereafter, an informal reconstruction of Kant's general logic is given from the aspect of the principles of contradiction, of sufficient reason, and of excluded middle. It is shown that Kant's composition of logic consists in a gradual strengthening of logical principles, starting from a weak principle of contradiction that tolerates a sort of contradictions in predication, and then proceeding to the (constructive) principle of sufficient reason, and to a classical-like logic, which includes the principle of excluded middle. A first-order formalisation is applied to this reconstruction, which reveals implicit modalities in Kant's account of logic, and confirms the implementability of Kant's logic into a sound and complete formal system.     

On Bolzano's Concept of a Sum

Alongside his groundbreaking work in logic, Bernard Bolzano (1781–1848) made important contributions to ontology, notably with his theory of collections. Recent work has done much to elucidate Bolzano's conceptions, but his notion of a sum has proved stubbornly resistant to complete understanding. This paper offers a new interpretation of Bolzano's concept of a sum. I argue that, although Bolzano's presentation is defective, his conception is unexceptionable, and has important applications, notably in his work on the foundations of arithmetic.     

Multidisciplinary creativity: the case of Herbert A. Simon

In the twentieth century, no person epitomized more dramatically the “Renaissance mind” than Herbert A. Simon (1916–2001). In aworking life spanning over 60 years, Simon made seminal contributions to administrative theory, axiomatic foundations of physics, economics, sociology, econometrics, cognitive psychology, logic of scientific discovery, and artificial intelligence. Simon's life of the mind, thus, affords nothing less than a “laboratory” in which to observe and examine at close quarters the phenomenon of multidisciplinary creativity. In this paper, we attempt to shed some light on the nature of Simon's creativity and the nature of his particular Renaissance mind. In particular, we have attempted here to articulate the cognitive style underlying Simon's multidisciplinary creativity.     

Logic as a Universal Medium or Logic as a Calculus? Husserl and the Presuppositions of “the Ultimate Presupposition of Twentieth Century Philosophy”

This paper discusses Jean van Heijenoort's (1967) and Jaakko and Merrill B. Hintikka's (1986, 1997) distinction between logic as a universal language and logic as a calculus, and its applicability to Edmund Husserl's phenomenology. Although it is argued that Husserl's phenomenology shares characteristics with both sides, his view of logic is closer to the model‐theoretical, logic‐as‐calculus view. However, Husserl's philosophy as transcendental philosophy is closer to the universalist view. This paper suggests that Husserl's position shows that holding a model‐theoretical view of logic does not necessarily imply a calculus view about the relations between language and the world. The situation calls for reflection about the distinction: It will be suggested that the applicability of the van Heijenoort and the Hintikkas distinction either has to be restricted to a particular philosopher's views about logic, in which case no implications about his or her more general philosophical views should be inferred from it; or the distinction turns into a question of whether our human predicament is inescapable or whether it is possible, presumably by means of model theory, to obtain neutral answers to philosophical questions. Thus the distinction ultimately turns into a question about the correct method for doing philosophy.     

Projective Identification on Different Levels

Freud's investigation of that which lies beyond the pleasure principle is, among other things, an attempt to understand how thoughts on matter, biology, psychology and mythology become linked, despite the fact that each of these systems are independent and self-sufficient, each one working according to its own logic. Free energy, that we may liken to a kind of noise, is bound and organized in a process where subjective meaning is created. During this process, a meaningful connection between inner and outer reality is established. However, subjectivity also creates problems, since the individual needs to find his or her own self-realization, his or her own path towards the grave. Self-realization contains an aggressive potential, which—reminiscent of the workings of the immune system—may be aimed at everything that is not-self; at the unfamiliar or that which causes discomfort; at that which blocks the path towards the individual's mastery of the world.     

Completeness: from Gödel to Henkin

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