Portal:Logic

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Logic

Logic (from the Ancient Greek: λογική, translit. logikḗ), is the systematic study of the form of valid inference, and the most general laws of truth. A valid inference is one where there is a specific relation of logical support between the assumptions of the inference and its conclusion. In ordinary discourse, inferences may be signified by words such as therefore, hence, ergo, and so on.

There is no universal agreement as to the exact scope and subject matter of logic (see § Rival conceptions, below), but it has traditionally included the classification of arguments, the systematic exposition of the 'logical form' common to all valid arguments, the study of proof and inference, including paradoxes and fallacies, and the study of syntax and semantics. Historically, logic has been studied in philosophy (since ancient times) and mathematics (since the mid-19th century), and recently logic has been studied in computer science, linguistics, psychology, and other fields.

Selected article

In the formal languages used in mathematical logic and computer science, a well-formed formula or simply formula^[2] (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

\ S

is a wff with respect to a given formal grammar

\ G

is equivalent to saying that

\ S

belongs to the language generated by

\ G

. A formal language can be identified with the set of its wffs.

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Selected biography

Bertrand Arthur William Russell, 3rd Earl Russell OM FRS (18 May 1872 – 2 February 1970), was a British philosopher, logician, mathematician and advocate for social reform.

A prolific writer, he was also a populariser of philosophy and a commentator on a large variety of topics, ranging from very serious issues to those much less so. Continuing a family tradition in political affairs, he was a prominent anti-war activist, championing free trade between nations and anti-imperialism.

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Did you know?

...that the Law of noncontradiction is the same as the Law of contradiction?
...that NAND alone or NOR alone make a functionally complete set of logical operators?
...that according to the continuum hypothesis, there is no cardinal number in between aleph null and the cardinality of the continuum?
...that all 24 valid syllogistic forms have names like 'Camestros' and 'Felapton'?
...that if a statement P implies another statement Q, and a third statement R also implies Q, and either P or R is true; then Q has to be true?
...that the dunce cap was named after a logician?
...that the collective noun for a group of logicians is a "sequitur of logicians"

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► Logic-related lists

► Logicians

► Assumption

► Classical logic

► Concepts in logic

► Dichotomies

► Difference

► Fallacies

► History of logic

► Logic literature

► Mathematical logic

► Non-classical logic

► Logic organizations

► Logical paradoxes

► Philosophical logic

► Philosophy of logic

► Logic puzzles

► Reasoning

► Logic and statistics

► Wikipedia books on logic

► Logic stubs

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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
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References

^ Godel, Escher, Bach: An Eternal Golden Braid, Douglas Hofstadter
^ 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.