Friedrich Reinmuth

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.

Building on the work of Peter Hinst and Geo Siegwart, we develop a pragmatised natural deduction calculus, i.e. a natural deduction calculus that incorporates illocutionary operators at the formal level, and prove its adequacy. In contrast to other linear calculi of natural deduction, derivations in this calculus are sequences of object-language sentences which do not require graphical or other means of commentary in order to keep track of assumptions or to indicate subproofs. (Translation of our German paper "Ein Redehandlungskalkül. Ein pragmatisierter Kalkül des natürlichen Schließens nebst Metatheorie"; online available at http://philpapers.org/rec/CORERE.)

We argue that the need for commentary in commonly used linear calculi of natural deduction is connected to the “deletion” of illocutionary expressions that express the role of propositions as reasons, assumptions, or inferred propositions. We first analyze the formalization of an informal proof in some common calculi which do not formalize natural language illocutionary expressions, and show that in these calculi the formalizations of the example proof rely on commentary devices that have no counterpart in the original proof. We then present a linear natural deduction calculus that makes use of formal illocutionary expressions in such a way that unique readability for derivations is guaranteed – thus showing that formalizing illocutionary expressions can eliminate the need for commentary.

Using a short excerpt from Anselm's Responsio as an example, this paper tries to present logical reconstruction 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. As such, 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. Yet, even though logical reconstruction is dependent on methods of formalization, it allows us to use formal methods for the analysis and assessment of natural language texts that are not readily formalizable and is thus an important tool when it comes to applying the concepts and methods of formal logic to such texts.

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.

Logical reconstruction is a fundamental philosophical method for achieving clarity concerning the prerequisites, presuppositions and the logical structure of natural language arguments. The scope and limits of this method have become visible not least through its intense application to Anselm of Canterbury’s notorious proofs for the existence of God. This volume collects, on the one hand, reconstructions of Anselmian arguments that take account of the problems of reconstruction and, on the other hand, theoretical reflections on reconstruction with a view to Anselm. We hope that this will allow the reader to critically assess the merits of the theoretical accounts in the light of the reconstructions and the merits of the reconstructions in the light of the theoretical accounts. In general, by considering the example of an outstanding thinker in one or the other way, this volume aims at advancing the methodology and the practice of logical reconstruction. The following remarks explain and motivate this undertaking: What purposes does logical reconstruction serve? What purposes does the reflection on logical reconstruction serve? In which ways can the practice and theory of reconstruction profit particularly from studying Anselm’s reasoning? How can the resulting problems be addressed? – Finally, a short overview over the contributions to this volume is offered.

Claims that agents must accept or reject certain propositions “on pain of self-contradiction” play a key role in Alan Gewirth’s dialectically necessary method. The aim of this paper is to investigate Gewirth’s method with respect to the relation between such claims, entailment and self-contradiction. I will identify certain bridge principles connecting obligatory acceptance, rejection and entailment that seem to be presupposed by Gewirth. Contrary to what seems to be Gewirth’s view, these principles, e. g., that one must accept simple and direct consequences of propositions that one must accept, do not follow from minimal rationality demands with respect to the avoidance of self-contradiction. Moreover, the bridge principles themselves appear to be rather problematic. Still, plausible dialogical versions of them can be developed. This dialogical treatment is not confined to the transfer of obligatory acceptance and rejection via entailment, but can be extended to primary acceptance with respect to the starting premises. It might seem questionable whether such a dialogical strategy is acceptable to a strict Gewirthian, since agents would have to accept certain propositions not “on pain of self-contradiction,” but on pain of violating dialogical principles which would have to be justified independently. However, even Gewirth’s demands with respect to the avoidance of self-contradiction go beyond what the rules of logic require. It seems that the dialectically necessary method cannot proceed without acknowledging a normative sphere of discursive practices.

Peregrin and Svoboda propose an inferential and holistic approach to formalization, and a similar approach (to correctness) is considered by Brun. However, while the inferential criteria of adequacy explicitly endorsed by these authors may be holistic "in spirit," they are formulated for single formulas. More importantly, they allow the trivialization of equivalence and face problems when materially correct arguments come into play. Against this background, this paper tries to motivate holistic inferential criteria that compel us to distinguish carefully between non-trivially equivalent formalizations as well as between materially and logically correct arguments on an inferential basis.