DICT.TW Dictionary Taiwan

 re·duc·tio ad ab·sur·dum /rɪˈdʌktiˌoˌædəbˈsɚ/

 Dem·on·stra·tion n.
 1. The act of demonstrating; an exhibition; proof; especially, proof beyond the possibility of doubt; indubitable evidence, to the senses or reason.
    Those intervening ideas which serve to show the agreement of any two others are called =\“proofs;” and where agreement or disagreement is by this means plainly and clearly perceived, it is called demonstration.\=   --Locke.
 2. An expression, as of the feelings, by outward signs; a manifestation; a show.  See also sense 7 for a more specific related meaning.
    Did your letters pierce the queen to any demonstration of grief?   --Shak.
    Loyal demonstrations toward the prince.   --Prescott.
 3. Anat. The exhibition and explanation of a dissection or other anatomical preparation.
 4. (Mil.) a decisive exhibition of force, or a movement indicating an attack.
 5. Logic The act of proving by the syllogistic process, or the proof itself.
 6. Math. A course of reasoning showing that a certain result is a necessary consequence of assumed premises; -- these premises being definitions, axioms, and previously established propositions.
 Direct demonstration, or  Positive demonstration, Logic & Math., one in which the correct conclusion is the immediate sequence of reasoning from axiomatic or established premises; -- opposed to Indirect demonstration, or Negative demonstration (called also reductio ad absurdum), in which the correct conclusion is an inference from the demonstration that any other hypothesis must be incorrect.
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 reductio ad absurdum
      n : (reduction to the absurd) a disproof by showing that the
          consequences of the proposition are absurd; or a proff of
          a proposition by showing that its negation leads to a
          contradiction [syn: reductio]