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What is philosophical logic? Philosophical logic is philosophy that is logic, and logic that is philosophy. It is where philosophy and logic come together and become one. Philosophical logic is not a special kind of logic, some species distinct from mathematical logic, symbolic logic, formal logic, informal logic, modern logic, ancient logic, or logic with any other familiar modifier. There is only logic. Logic is the theory of consequence relations, of valid inferences. As such, it can be investigated and presented in many ways, although the mathematical methods of modern formal or symbolic logic have proved extraordinarily fruitful. Within logic so construed, there are still, of course, many different sorts - as witnessed by the variety of chapters of this volume. Philosophical logic comprises the sorts of logic that hold greatest interest for philosophers. Philosophical logic develops formal systems and structures to be applied to the analysis of concepts and arguments that are central to philosophical inquiry. So, for example, such traditional philosophical concepts as necessity, knowledge, obligation, time and existence, not to mention reasoning itself, are usefully investigated through modal logic, epistemic logic, deontic logic, temporal logic, free logic, probability logic, nonmonotonic logic, etc. Similarly, logical investigation has contributed immeasurably to our understanding ... log in or subscribe to read full text