Document Type : Translation & Critic

Authors

• Lotfollah Nabavi ¹
• Zinat Ayatollahi ²
• Mohammad Saeedi Mehr ³
• Mohsen Javadi ⁴

¹ Associate Professor of Logic, Tarbiat Modares University

² Ph.D Student in Logic, Tarbiat Modares University

³ Associate Professor of Philosophy, Tarbiat Modares University

⁴ Professor of ethics, Islamic science and m’arif , Qom University

Abstract

In traditional Aristotelian logic, the absence of a logical relation between ‘is’ and ‘ought’ statements seems to be evident, due to some characteristics of the logic. Prior relying on this fact that modern logic does not possess such characteristics, present a paradox against the advocates of the logical gap between ‘is’ and ‘ought’. In this paper, we, first, explain this paradox and a number of philosophical solutions have been proposed to solve it. Then, we illustrate and evaluate the Beall’s ‘many-valued logic’, which has been introduced as a solution to this paradox. We’ll see that this paradox could be solved in the context of the ‘relevant logic’ too. But besides of this paradox, Prior presents two other arguments, which although these two logics solve the paradox, we’ll show that each of them is unable to response to these two other arguments.

Keywords

• Keywords: ‘Is-Ought’
• Problem
• Prior’s Dilemma
• classical logic
• many valued logic
• relevant logic