Philosophy of logic


Following the developments in formal logic with symbolic logic in the late nineteenth century and mathematical logic in the twentieth, topics traditionally treated by logic not being part of formal logic have tended to be termed either philosophy of logic or philosophical logic if no longer simply logic.
Compared to the history of logic, the demarcation between philosophy of logic and philosophical logic is of recent coinage and not always entirely clear. Characterisations include:
This article outlines issues in philosophy of logic or provides links to relevant articles or both.

Introduction

This article makes use of the following terms and concepts:
Aristotle said To say that that which is, is not or that which is not is, is a falsehood; and to say that which is, is and that which is not is not, is true
This apparent truism has not proved unproblematic.

Truthbearers

Logic uses such terms as true, false, inconsistent, valid, and self-contradictory. Questions arise as Strawson writes

Tarski's definition of truth

See:
Since the use, meaning, if not the meaningfulness, of the terms is part of the debate, it is possible only to give the following working definitions for the purposes of the discussion:
The concept of logical truth is intimately linked with those of validity, logical consequence and entailment.
Issues that arise include:
See also

Paradox

Meaning and reference

See

Quantifiers and quantificational theory

Modal logic

Deviant logics

Classical v. non-classical logics

Philosophical theories of logic

Figures in the philosophy of logic include :