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Logic (from "Classical Greek λόγος "logos; meaning 'speech/word') is the study of the principles and criteria of valid "inference and "demonstration. The term "logos" was also believed by the Greeks to be the universal power by which all reality was sustained and made coherent and consistent.
As a "formal science, logic investigates and classifies the structure of statements and arguments, both through the study of "formal systems of "inference and through the study of arguments in natural language. The field of logic ranges from core topics such as the study of "fallacies and "paradoxes, to specialized analysis of reasoning using "probability and to arguments involving "causality. Logic is also commonly used today in "argumentation theory. ^{[1]}
Traditionally, logic is studied as a branch of "philosophy, one part of the classical "trivium, which consisted of "grammar, logic, and "rhetoric. Since the midnineteenth century formal logic has been studied in the context of the "foundations of mathematics. In 1910 "Bertrand Russell and "Alfred North Whitehead attempted to establish logic as the cornerstone of mathematics formally with the publication of "Principia Mathematica. However, the system of Principia is no longer much used, having been largely supplanted by "set theory. The development of formal logic and its implementation in computing machinery is the foundation of "computer science.
Logical disjunction is an "operation on two "logical values, typically the values of two "propositions, that produces a value of false if and only if both of its operands are false. More generally a disjunction is a logical formula that can have one or more "literals separated only by ORs. A single literal is often considered to be a degenerate disjunction.
Together with Plato and "Socrates (Plato's teacher), Aristotle is one of the most important founding figures in "Western philosophy. He was the first to create a comprehensive system of Western philosophy, encompassing morality and aesthetics, logic and science, politics and metaphysics. Aristotle's views on the "physical sciences profoundly shaped medieval scholarship, and their influence extended well into the "Renaissance, although they were ultimately replaced by Newtonian Physics. In the biological sciences, some of his observations were confirmed to be accurate only in the nineteenth century. His works contain the earliest known formal study of logic, which was incorporated in the late nineteenth century into modern "formal logic. In metaphysics, "Aristotelianism had a profound influence on "philosophical and theological thinking in the Islamic and Jewish traditions in the "Middle Ages, and it continues to influence "Christian theology, especially "Eastern Orthodox theology, and the "scholastic tradition of the "Roman Catholic Church. All aspects of Aristotle's philosophy continue to be the object of active academic study today.