Logic
Overview

In philosophy
Philosophy
Philosophy is the study of general and fundamental problems, such as those connected with existence, knowledge, values, reason, mind, and language. Philosophy is distinguished from other ways of addressing such problems by its critical, generally systematic approach and its reliance on rational...

, Logic (from the Greek λογική logikē) is the formal systematic study of the principle
Principle
A principle is a law or rule that has to be, or usually is to be followed, or can be desirably followed, or is an inevitable consequence of something, such as the laws observed in nature or the way that a system is constructed...

s of valid inference
Inference
Inference is the act or process of deriving logical conclusions from premises known or assumed to be true. The conclusion drawn is also called an idiomatic. The laws of valid inference are studied in the field of logic.Human inference Inference is the act or process of deriving logical conclusions...

and correct reasoning. Logic is used in most intellectual activities, but is studied primarily in the disciplines of philosophy
Philosophy
Philosophy is the study of general and fundamental problems, such as those connected with existence, knowledge, values, reason, mind, and language. Philosophy is distinguished from other ways of addressing such problems by its critical, generally systematic approach and its reliance on rational...

, mathematics
Mathematics
Mathematics is the study of quantity, space, structure, and change. Mathematicians seek out patterns and formulate new conjectures. Mathematicians resolve the truth or falsity of conjectures by mathematical proofs, which are arguments sufficient to convince other mathematicians of their validity...

, semantics
Semantics
Semantics is the study of meaning. It focuses on the relation between signifiers, such as words, phrases, signs and symbols, and what they stand for, their denotata....

, and computer science
Computer science
Computer science or computing science is the study of the theoretical foundations of information and computation and of practical techniques for their implementation and application in computer systems...

. It examines general forms which argument
Argument
In philosophy and logic, an argument is an attempt to persuade someone of something, or give evidence or reasons for accepting a particular conclusion.Argument may also refer to:-Mathematics and computer science:...

s may take, which forms are valid, and which are fallacies. In philosophy, the study of logic is applied in most major areas: ontology
Ontology
Ontology is the philosophical study of the nature of being, existence or reality as such, as well as the basic categories of being and their relations...

, epistemology, ethics
Ethics
Ethics, also known as moral philosophy, is a branch of philosophy that addresses questions about morality—that is, concepts such as good and evil, right and wrong, virtue and vice, justice and crime, etc.Major branches of ethics include:...

, metaphysics
Metaphysics
Metaphysics is a branch of philosophy concerned with explaining the fundamental nature of being and the world, although the term is not easily defined. Traditionally, metaphysics attempts to answer two basic questions in the broadest possible terms:...

.
Quotations

Logic hasn't wholly dispelled the society of witches and prophets and sorcerers and soothsayers.

Raymond F. Jones, The Non-Statistical Man

Logic is a large drawer, containing some useful instruments, and many more that are superfluous. A wise man will look into it for two purposes, to avail himself of those instruments that are really useful, and to admire the ingenuity with which those that are not so, are assorted and arranged.

Charles Caleb Colton, Lacon

Logic is logic. That's all I say.

Oliver Wendell Holmes, Sr.|Oliver Wendell Holmes, The One-Hoss Shay

Logic is one thing and commonsense another.

Elbert Hubbard, The Note Book (1927)

The want of logic annoys. Too much logic bores. Life eludes logic, and everything that logic alone constructs remains artificial and forced.

André Gide

Logic, like whiskey, loses its beneficial effect when taken in too large quantities.

Edward John Moreton Drax Plunkett, Lord Dunsany, "Weeds & Moss", My Ireland

Metaphysics may be, after all, only the art of being sure of something that is not so, and logic only the art of going wrong with confidence.

Joseph Wood Krutch, The Modern Temper (1929)

Pure logic is the ruin of the spirit.

Antoine de Saint-Exupéry Flight to Arras (1942), as translated by Lewis Galantière

One cannot use one's logic to explain actions driven by others' logic.

Sir. Acel Quailin KBE