deduction

/di duk"sheuhn/, n.
1. the act or process of deducting; subtraction.
2. something that is or may be deducted: She took deductions for a home office and other business expenses from her taxes.
3. the act or process of deducing.
4. something that is deduced: His astute deduction was worthy of Sherlock Holmes.
5. Logic.
a. a process of reasoning in which a conclusion follows necessarily from the premises presented, so that the conclusion cannot be false if the premises are true.
b. a conclusion reached by this process. Cf. induction (def. 4).
[1400-50; late ME deduccioun ( < AF) < L deduction- (s. of deductio) a leading away. See DEDUCT, -ION]

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In logic, a type of inference or argument that purports to be valid, where a valid argument is one whose conclusion must be true if its premises are true (see validity).

Deduction is thus distinguished from induction, where there is no such presumption. Valid deductive arguments may have false premises, as demonstrated by the example: "All men are mortal; Cleopatra is a man; therefore, Cleopatra is mortal." Invalid deductive arguments sometimes embody formal fallacies (i.e., errors of reasoning based on the structure of the propositions in the argument); an example is "affirming the consequent": "If A then B; B; therefore, A" (see fallacy; formal and informal).

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reason
      in logic, a rigorous proof, or derivation, of one statement (the conclusion) from one or more statements (the premises)—i.e., a chain of statements, each of which is either a premise or a consequence of a statement occurring earlier in the proof. This usage is a generalization of what the Greek philosopher Aristotle called the syllogism, but a syllogism is now recognized as merely a special case of a deduction. Also, the traditional view that deduction proceeds “from the general to the specific” or “from the universal to the particular” has been abandoned as incorrect by most logicians. Some experts regard all valid inference as deductive in form and, for this and other reasons, reject the supposed contrast between deduction and induction. See also axiomatic method; formal system; inference.

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Universalium. 2010.

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  • déduction — [ dedyksjɔ̃ ] n. f. • 1355; lat. deductio I ♦ Action de soustraire une somme d une autre. ⇒ décompte, défalcation, retranchement, soustraction. Faire la déduction des sommes déjà payées. Déduction faite des arrhes versées. Somme qui entre, vient… …   Encyclopédie Universelle

  • deduction — de·duc·tion n 1: an amount allowed by tax laws to be subtracted from income in order to decrease the amount of income tax due see also internal revenue code in the important laws section compare credit, ex …   Law dictionary

  • Deduction — • An argument or reasoning process, that kind of mediate inference by which from truths already known we advance to a knowledge of other truths necessarily implied in the former; the mental product or result of that process. Also a method, the… …   Catholic encyclopedia

  • deduction — 1 Deduction, abatement, rebate, discount are comparable when they mean an amount subtracted from a gross sum. Deduction is interchangeable with any of the others but not without some loss in precision. An abatement is a deduction from a levied… …   New Dictionary of Synonyms

  • Deduction — Déduction Cette page d’homonymie répertorie les différents sujets et articles partageant un même nom …   Wikipédia en Français

  • Deduction — may refer to: in logic: Deductive reasoning, inference in which the conclusion is of no greater generality than the premises Natural deduction, an approach to proof theory that attempts to provide a formal model of logical reasoning as it… …   Wikipedia

  • Deduction — De*duc tion, n. [L. deductio: cf. F. d[ e]duction.] 1. Act or process of deducing or inferring. [1913 Webster] The deduction of one language from another. Johnson. [1913 Webster] This process, by which from two statements we deduce a third, is… …   The Collaborative International Dictionary of English

  • déduction — DÉDUCTION. s. f. Soustraction. On lui a payé tant en déduction du principal. La succession, déduction faite des frais, monte à telle somme. [b]f♛/b] Il signifie aussi, Narration, énumération en détail. Faire une longue déduction de ses raisons,… …   Dictionnaire de l'Académie Française 1798

  • deduction — Deduction. Soustraction. On luy a payé tant en deduction du principal. Il signifie aussi, Narration, enumeration en detail. Faire une longue deduction de ses raisons …   Dictionnaire de l'Académie française

  • deduction — deduction, deductive The use of logical rules to arrive at a set of premisses from which certain conclusions must follow. Deduction begins with theory , moves to hypotheses derived from the theory, and then tests hypotheses via prediction and… …   Dictionary of sociology

  • deduction — early 15c., action of deducting, from M.Fr. déduction or directly from L. deductionem (nom. deductio), noun of action from pp. stem of deducere (see DEDUCE (Cf. deduce)). Meaning that which is deducted is from 1540s. As a term in logic, from L.L …   Etymology dictionary

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