- Philosophy of logic
"This article is about philosophy of logic, not
Philosophy of logic is the branch of
philosophythat is concerned with the scope and nature of logic. Some fundamental questions with which it is concerned are:
* Is there only one "true" logic, or are many logics equally correct?
* Is it possible to have genuine disagreements about whether a logical principle (such as the
law of excluded middle) is correct?
* What makes an expression a
* What are the proper accounts of
logical consequence, quantification, and other logical concepts?
* What is the scope of logic (e.g., does it encompass
second-order logicreally logic?
* Is logic a matter of convention?
* Is logic empirical?
* What is the nature of logical necessity?
* What is the relationship between the verbal rules of logic and the mental ability to reason logically?
Truth, Propositions and Meaning
Tarski's definition of Truth
What is and is not considered a "logical truth" (also called an "analytic truth" or a "necessary truth") has been a matter for clarification, even up to the early part of the 20th Century.
A "logical truth" was considered by
Ludwig Wittgensteinto be a statement which is true in all possible worlds [ Ludwig Wittgenstein, Tractatus Logico-Philosophicus] . This is contrasted with "synthetic claim" (or " fact") which is only true in "this" world as it has historically unfolded.
Later, with the rise of formal logic a "logical truth" was considered to be a statement which is true under all possible
Logical truths are "necessarily" true. A
propositionsuch as “If p and q, then p.” and the proposition “All husbands are married.” are considered to be logical truths because they are true because of their meanings and not because of any facts of the world. They are such that they could not be untrue. Logicis concerned with the patterns in reasonthat can help tell us if a propositionis true or not. However, logic does not deal with truth in the absolute sense, as for instance a metaphysician does. Logicians use formal languages to express the truths which they are concerned with, and as such there is only truth "under some interpretation" or truth "within some logical system."
Are Logical Truths a priori or a posteriori knowledge? Synthetic or Analytic
Is logic empirical?
The analytic/synthetic distinction
Willard Van Orman Quine, Proposition
Identity of indiscernibles
Rationality and Logic
Plato's Beard & The problem of non-being
Do unicorns have horns and did Hamlet see a real ghost?
Does the square root of minus one have the same ontological status at the square root of two
Do predicates have properties?
The status of the Laws of Logic
Platonic realism, Philosophical realism
The Law of Excluded Middle
Law of excluded middle
Quantifiers, Quantification Theory and Identity
Validity, Inference and Entailment
Modality, Intensionality and Propositional Attitude
The problem of the material conditional
Important figures in the philosophy of logic include (but are not limited to):
Augustus De Morgan
* W V Quine
John Stuart Mill
Willard Van Orman Quine
Is logic empirical?
* Haack, Susan. 1978. "Philosophy of Logics".
Cambridge University Press. (ISBN 0-521-29329-4)
* Quine, W. V. O. 2004. "Philosophy of Logic". 2nd ed.
Harvard University Press. (ISBN 0-674-66563-5)
* [http://www.rep.routledge.com/article/X046 Routledge Encyclopedia of Philosophy entry]
* [http://www.organelle.org/organelle/glossary/unA.html essay on the nature of logic (from organelle.org)]
* [http://www.rbjones.com/rbjpub/philos/logic/ Philosophy of logic] (from rbjones.com)
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