# Portal:Logic

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## Logic

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 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.

## Selected article

In the formal languages used in mathematical logic and computer science, a well-formed formula or simply formula[3] (often abbreviated wff, pronounced "wiff" or "wuff") is an idea, abstraction or concept which is expressed using the symbols and formation rules (also called the formal grammar) of a particular formal language. To say that a string of symbols ${\displaystyle \ S}$ is a wff with respect to a given formal grammar ${\displaystyle \ G}$ is equivalent to saying that ${\displaystyle \ S}$ belongs to the language generated by ${\displaystyle \ G}$. A formal language can be identified with the set of its wffs.

## Selected biography

Ramon Llull (Catalan: [rəˈmon ˈʎuʎ]; ca. 1232[4] – 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.

## Things to do

 Here are some tasks awaiting attention: Article requests : Anonymous authority  • Anti-Procreation Movement  • Appeal to classical allusions  • Archimedean Fulcrum  • Asserting an alternative  • Bad reasons fallacy  • Cartesian logic  • Common thread reasoning  • Conjunctive forks  • Converting a conditional  • Doctrine of Unexpected Consequences  • Dream logic  • Equivocity  • Fallacy of assuming a common cause  • Fallacy of biased generalization  • Conflicting conditions  • Failure to elucidate  • Too broad  • Too narrow  • Fallacies of distraction  • Fallacies of explanation  • Limited depth  • Limited scope  • Non-support  • Subverted support  • Untestability  • Fallacy of personal preference assumptions  • Fallacy of quantificational logic  • Fallacy of reverse causation  • Fallacy of the alternative syllogism  • Fallacy of the disjunctive syllogism  • Fallacy of the propositional logic  • Free time (fallacy)  • Futurist extrapolation  • Heads in the sand critique  • Ignoring common cause  • Illicit process  • Improper disjunctive syllogism  • Improper transposition  • Inferring from a metaphor  • Intuitionistic modal logic  • Jactication  • Kicking the problem upstairs  • Lennon/McCartney fallacy  • Liminocentricity  • List of valid argument forms Done  • List of invalid argument forms  • Logical notation  • Meinongian arguments  • Mereological arguments  • Negating antecedent and consequent  • Neutrality Schmeutrality  • One-sidedness  • Open Block Logic  • Oppositional logic  • Perfectly rigorous  • Physiological Egoism  • Plurivocity  • Postmodern mathematics  • Prejudicial language  • Pseudorefutation  • Quote-name  • Repetition (fallacy)  • Science fiction moralizing  • Significant difference reasoning  • Some are/some are not  • Sublime experience  • Superalternation  • Swiftian logic  • Tendentious appeal to possibilities  • truth-apt  • Truthmapping  • Unwarranted contrast  • Upwards inherited  • Volitive  • Weaseler  • John Arrington Woodward Other : Add links to this portal by placing {{Portal|Logic}} in the See also sections of relevant articles

## References

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. ^ Godel, Escher, Bach: An Eternal Golden Braid, Douglas Hofstadter
3. ^ Because non-well-formed formulas are rarely considered, some authors ignore them altogether. For these authors, "formula" and "well-formed formula" are synonyms. Other authors use the term "formula" for any string of symbols in the language; certain of these strings are then singled out as the well-formed formulas.
4. ^ 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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