Philosophical Logic

Philosophical logic is a term introduced by Bertrand Russell to represent his idea that the workings of natural language and thought can only be adequately represented by an artificial language; essentially it was his formalization program for the natural language. Today the term is used with several different meanings.

One modern meaning, espoused mainly by philosophers, is that philosophical logic is the study of the more specifically philosophical aspects of logic in contrast with symbolic logic; for example Sybil Wolfram lists the study of the concepts of argument, meaning, and truth. Colin McGinn includes identity, existence, predication, necessity, and truth as the main topics of his book, which he writes was aimed "to bring philosophy back into philosophical logic". John Woods writes that philosophical logic investigates properties such as truth, meaning and reference in natural languages. As contrasting example he argues that Frege's Begriffsschrift is an example of mathematical logic, while Frege's discussion of sense and reference belongs to the philosophical logic realm. Woods also points out that there's substantial overlap between philosophy of language and philosophical logic. Susan Haack argued that there is no distinction between philosophical logic seen this way and philosophy of logic. A. C. Grayling disagrees however, writing that when "one does philosophy of logic, one is philosophizing about logic; but when one does philosophical logic one is philosophizing." He concedes however that the distinction is not too sharp. In general there is no agreement whether these two fields coincide or not.

Another meaning assigned to philosophical logic today is that it addresses mainly extensions and alternatives to classical logic, the so-called non-classical logics. In this sense, philosophical logic is a technical subject. Texts such as John P. Burgess' Philosophical Logic, the Blackwell Companion to Philosophical Logic, or the multi-volume Handbook of Philosophical Logic(edited by Dov M. Gabbay and Franz Guenthner) address this latter meaning of the term, with classical logic included as a core component however. According to Burgess, philosophical logic in this sense, has its center of gravity in theoretical computer science, because many non-classical logics find applications there. The Springer Journal of Philosophical Logic largely addresses this conception of philosophical logic.

Yet another contemporary meaning proposed by Dale Jacquette is that philosophical logic is philosophy in which any recognized methods of logic are used to solve or advance the discussion of philosophical problems.