Avicenna (d. 1037) and Tūsī (d. 1274) have different doctrines on the contradiction and conversion of the absolute proposition. Following Avicenna's presentation of the doctrine in Pointers and reminders, and comparing it with what is given in Tūsī's commentary, allow us to pinpoint a major reason why Avicenna and Tūsī have different treatments of the modal syllogistic. Further comparison shows that the syllogistic system Rescher described in his research on Arabic logic more nearly fits Tūsī than Avicenna. This in turn (...) has consequences for analysing Avicenna's logic, and for writing the history of a fascinating period of change and diversity in the discipline in the medieval Islamic world. (shrink)

Recent students of late medieval intellectual history have treated Oxford theologians' Sentences lectures from the 1320s to 1330s as revealing the interface of the theological, logical, and scientific thinking characteristic of a historically momentous ‘New English Theology’. Its conceptual achievement, historians generally concur, was the casting off of the speculative metaphysics of such thirteenth-century authors as Robert Grosseteste and Roger Bacon; its methodological novelty made it akin to twentieth-century analytic philosophy and seminal for the early Scientific Revolution. Yet the metaphysically (...) cast thirteenth-century sciences of perspectiva and astrologia persisted among scholars long into the early modern period. To show how this apparent paradox may be dissolved, this article details the intersection of thirteenth-century metaphysics and fourteenth-century analysis in the lectures of a controversial and influential proponent of the Oxford theology of the 1330s. (shrink)

This article develops a new perspective on theism that makes the simple juxtaposition of theism and atheism problematic, and helps bridge philosophy of religion and the empirical study of religious phenomena. The basic idea is developed inspired by Terrence Deacon's book Incomplete Nature and its description of “ententional” phenomena, together with some ideas from the cognitive science of religion, especially those related to agency and “theological correctness.” It is argued that God should not be understood as a “homunculus” that stops (...) an otherwise infinite regress of arguments. (shrink)

A century ago, Charles S. Peirce proposed a logical approach to modalities that came close to possible-worlds semantics. This paper investigates his views on modalities through his diagrammatic logic of Existential Graphs (EGs). The contribution of the gamma part of EGs to the study of modalities is examined. Some ramifications of Peirce’s remarks are presented and placed into a contemporary perspective. An appendix is included that provides a transcription with commentary of Peirce’s unpublished manuscript on modality from 1901.

A century ago, Charles S. Peirce proposed a logical approach to modalities that came close to possible-worlds semantics. This paper investigates his views on modalities through his diagrammatic logic of Existential Graphs. The contribution of the GAMMA part of EGs to the study of modalities is examined. Some ramifications of Peirce's remarks are presented and placed into a contemporary perspective. An appendix is included that provides a transcription with commentary of Peirce's unpublished manuscript on modality from 1901.

In this article, the author studies some central concepts in Avicenna's and sī's modal logics as presented in Avicenna's Al-Ish r t wa'l Tan īh t ( Pointers and Reminders ) and in sī's commentary. In this work, Avicenna introduces some remarkable distinctions in order to interpret Aristotle's modal syllogistic in the Prior Analytics . The author outlines a new interpretation of absolute sentences as temporally indefinite sentences and argues on the basis of this that Avicenna seems to subscribe to (...) the Principle of Plenitude. He also shows that he has no valid proof of the modal conversion rules and that he uses some rather ad hoc distinctions to show that Aristotle's modal syllogistic is correct. The author also notes some interesting differences between Avicenna's and sī's approaches to modal logic. (shrink)

Epistemic logic is the logic of knowledge and belief. It provides insight into the properties of individual knowers, has provided a means to model complicated scenarios involving groups of knowers and has improved our understanding of the dynamics of inquiry.