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Logic (from Classical Greek ????? 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 mid-nineteenth 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.

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The Venn diagram of p or q
In logic and mathematics, or, also known as logical disjunction or inclusive disjunction is a logical operator that results in true whenever one or more of its operands are true. In grammar, or is a coordinating conjunction.

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.

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Ramon Llull.jpg
Ramon Llull (Catalan: [r?'mon '?u?]; ca. 1232[2] - ca. 1315) (Anglicised Raymond Lully, Raymond Lull; in Latin Raimundus or Raymundus Lullus or Lullius) was a Majorcan writer and philosopher, logician and a Franciscan tertiary. He wrote the first major work of Catalan literature. Recently-surfaced manuscripts show him to have anticipated by several centuries prominent work on elections theory. He is sometimes considered a pioneer of computation theory, especially given his influence on Gottfried Leibniz. Llull is well known also as a glossator of Roman Law.

Within the Franciscan Order, he is honored as a martyr. He was beatified in 1857 by Pope Pius IX and his feast day was assigned to 30 June and is celebrated by the Third Order of St. Francis.


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  1. ^ J. Robert Cox and Charles Arthur Willard, eds. Advances in Argumentation Theory and Research, Southern Illinois University Press, 1983 ISBN 0809310503, ISBN-13 978-0809310500
  2. ^ Born 1232 per Mark D. Johnston in Routledge Encyclopedia of Philosophy. London: Routledge, 1998. Older sources (such as versions of Encyclopædia Britannica at least up to 1955) give 1235; the current Britannica gives 1232/33.

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