Reviewed Works:Gaisi Takeuti, Proof Theory.Georg Kreisel, Proof Theory: Some Personal Recollections.Wolfram Pohlers, Contributions of the Schutte School in Munich to Proof Theory.Stephen G. Simpson, Subsystems of $\mathbf{Z}_2$ and Reverse Mathematics.Solomon Feferman, Proof Theory: A Personal Report.

Natural deduction is the type of logic most familiar to current philosophers, and indeed is all that many modern philosophers know about logic. Yet natural deduction is a fairly recent innovation in logic, dating from Gentzen and Jaśkowski in 1934. This article traces the development of natural deduction from the view that these founders embraced to the widespread acceptance of the method in the 1960s. I focus especially on the different choices made by writers of elementary textbooks—the standard conduits of (...) the method to a generation of philosophers—with an eye to determining what the ‘essential characteristics’ of natural deduction are. (shrink)

Was ist Wahrheit? Zufolge welcher Standards erkennt man, was wahr oder falsch ist? Wie lassen sich derartige Kriterien rechtfertigen? Die vornehmlich durch die Wende zur Sprache und die Ausbildung einer Metatheorie der analytischen Wissenschaften geprägte neuere Erörterung dieser Hauptfragen zur Wahrheit führt auf Vorfragen: Von welchen Gebilden sagen wir in welcher Weise, sie seien wahr oder falsch? Was sind und was leisten Definitionen, Kriterien, Regeln, Bedingungen der Wahrheit und Falschheit? Die vorliegende Schrift entfaltet einen systematischen Rahmen, in dem die Vorfragen (...) zur Wahrheit beantwortet und die Hauptfragen in neuer Weise organisiert werden. (shrink)

The thesis aims at a methodological reflection of logical reconstruction and tries to develop this method in detail, especially with regard to the reconstruction of natural language arguments. First, the groundwork for the thesis is laid by presenting and, where necessary, adapting its foundations with regard to the philosophy of language and the theory of argument. Subsequently, logical reconstruction, especially the logical reconstruction of arguments, is presented as a hermeneutic method and as a tool for the application of (formal) logic (...) and argumentation theory to natural language arguments. Logical reconstruction is presented as a special type of exegetical interpretation by paraphrase that is subject to (adapted) hermeneutic maxims and presumption rules that govern exegetical interpretation in general. However, in contrast to the interpretation of texts by natural language paraphrases, logical reconstruction leads to interpretantia that are logically explicit formal language texts and can be analyzed using formal methods and meta-theoretical concepts that are not directly applicable to natural language texts. By providing explicit and precise records of different readings, logical reconstruction can thus help to clarify (and maybe even solve) persistent interpretation controversies. Through an adaptation and specification of hermeneutic maxims and presumption rules, the thesis aims at providing suitable means for the systematic guidance and evaluation of logical reconstructions of argumentative texts. As a genuinely interpretative undertaking, logical reconstruction will be distinguished from the non-interpretative enterprise of formalization and from the development of theories of logical form, which provide a framework in which formalization and reconstruction take place. As exegetical interpretations, logical reconstructions of texts that are not readily formalizable can still be assessed with respect to their hermeneutic quality. The hermeneutic method of logical reconstruction can thus widen the scope for the application of logic and argumentation theory, because it allows us to use formal methods for the analysis and assessment of "difficult" natural language texts in a non-arbitrary, albeit indirect way. The last part of the thesis presents a manual for the logical reconstruction of natural language arguments, whose application is illustrated step by step. (shrink)

In 1934 a most singular event occurred. Two papers were published on a topic that had (apparently) never before been written about, the authors had never been in contact with one another, and they had (apparently) no common intellectual background that would otherwise account for their mutual interest in this topic.1 These two papers formed the basis for a movement in logic which is by now the most common way of teaching elementary logic by far, and indeed is perhaps all (...) that is known in any detail about logic by a number of philosophers (especially in North America). This manner of proceeding in logic is called ‘natural deduction’. And in its own way the instigation of this style of logical proof is as important to the history of logic as the discovery of resolution by Robinson in 1965, or the discovery of the logistical method by Frege in 1879, or even the discovery of the syllogistic by Aristotle in the fourth century BC. (shrink)

We outline a pragmatic-normative understanding of logic as a discipline that is completely anchored in the sphere of action, rules, means and ends: We characterize inferring as a speech act which is in need of regulation and we connect inferential rules with consequence relations. Furthermore, we present a scenario which illustrates how one actually assesses or can in principle assess the quality of logical rules with respect to justificatory questions. Finally, we speculate on the origin of logical rules as a (...) means of supporting our practice of inferring. (shrink)