Fallacy

• POS: Noun
• HYPHEN: fal=la=cy

CIDE DICTIONARY

Fallacy, n. [OE. fallace, fallas, deception, F. fallace, fr. L. fallacia, fr. fallax deceitful, deceptive, fr. fallere to deceive. See Fail.].

•  Deceptive or false appearance; deceitfulness; that which misleads the eye or the mind; deception.  [1913 Webster]

  "Winning by conquest what the first man lost,
  By fallacy surprised."  [1913 Webster]
•  An argument, or apparent argument, which professes to be decisive of the matter at issue, while in reality it is not; a sophism.

Syn. -- Deception; deceit; mistake.

OXFORD DICTIONARY

Fallacy, n. (pl. -ies)
1 a mistaken belief, esp. based on unsound argument.
2 faulty reasoning; misleading or unsound argument.
3 Logic a flaw that vitiates an argument.

Derivative

fallacious adj. fallaciously adv. fallaciousness n.

Etymology

L fallacia f. fallax -acis deceiving f. fallere deceive

THESAURUS

Fallacy

Albigensianism, Arianism, Catharism, Ebionitism, Erastianism, Gnosticism, Jovinianism, Lollardy, Manichaeanism, Manichaeism, Monophysism, Monophysitism, Pelagianism, Waldensianism, Wyclifism, aberrancy, aberration, antinomianism, apparent soundness, argument, argument by analogy, argumentum ad baculum, argumentum ad captandum, argumentum ad hominem, bad case, bamboozlement, befooling, begging the question, bluffing, calculated deception, casuistry, circular argument, circularity, circumvention, claptrap, conning, crowd-pleasing argument, deceiving, deception, deceptiveness, defectiveness, defrauding, delusion, delusiveness, deviancy, disingenuousness, distortion, dupery, elusion, emanatism, empty words, enmeshment, ensnarement, entanglement, entrapment, equivocalness, equivocation, errancy, erroneousness, error, evasion, evasive reasoning, fallaciousness, false doctrine, falsehood, falseness, falsity, fault, faultiness, flaw, flawedness, flimflam, flimflammery, fond illusion, fooling, formal fallacy, hallucination, hamartia, heresy, heterodoxy, hoodwinking, hylotheism, hysteron proteron, illusion, inconsistency, insincere argument, insincerity, inveracity, jesuitism, jesuitry, kidding, logical fallacy, material fallacy, mere rhetoric, mirage, misapplication, misbelief, miscalculation, misconception, misconstruction, misdoing, misfeasance, misinterpretation, misjudgment, mistake, misunderstanding, moonshine, mystification, non sequitur, obfuscation, obscurantism, outwitting, overreaching, oversubtlety, pantheism, paralogism, peccancy, perversion, petitio principii, phantasm, philosophism, plausibility, plausibleness, pseudosyllogism, putting on, quibble, rationalization, self-contradiction, self-deception, sin, sinfulness, snow job, solecism, song and dance, sophism, sophistical reasoning, sophistication, sophistry, special pleading, speciosity, specious reasoning, speciousness, spoofery, spoofing, spuriousness, subterfuge, subtlety, swindling, trickiness, tricking, truthlessness, unorthodoxy, untrueness, untruth, untruthfulness, verbal fallacy, vicious circle, vicious reasoning, victimization, vision, weak point, willful misconception, wishful thinking, wrong, wrongness

ROGET THESAURUS

Fallacy

& Sophistry

N intuition, instinct, association, hunch, gut feeling, presentiment, premonition, rule of thumb, superstition, astrology, faith (supposition), sophistry, paralogy, perversion, casuistry, jesuitry, equivocation, evasion, chicane, chicanery, quiddet, quiddity, mystification, special pleading, speciousness, nonsense, word sense, tongue sense, false reasoning, vicious reasoning, circular reasoning, petitio principii, ignoratio elenchi, post hoc ergo propter hoc, non sequitur, ignotum per ignotius, misjudgment, false teaching, sophism, solecism, paralogism, quibble, quirk, elenchus, elench, fallacy, quodlibet, subterfuge, subtlety, quillet, inconsistency, antilogy, a delusion, a mockery, and a snare, claptrap, cant, mere words, lame and impotent conclusion, meshes of sophistry, cobwebs of sophistry, flaw in an argument, weak point, bad case, overrefinement, hairsplitting, intuitive, instinctive, impulsive, independent of reason, anterior to reason, gratuitous, hazarded, unconnected, unreasonable, illogical, false, unsound, invalid, unwarranted, not following, inconsequent, inconsequential, inconsistent, absonous, absonant, unscientific, untenable, inconclusive, incorrect, fallacious, fallible, groundless, unproved, non sequitur, it does not follow, deceptive, sophistical, jesuitical, illusive, illusory, specious, hollow, plausible, ad captandum, evasive, irrelevant, weak, feeble, poor, flimsy, loose, vague, irrational, nonsensical, foolish, frivolous, pettifogging, quibbling, finespun, overrefined, at the end of one's tether, au bout de son latin, intuitively, by intuition, illogically, non constat, that goes for nothing.

Error

N error, fallacy, misconception, misapprehension, misstanding, misunderstanding, inexactness, laxity, misconstruction, miscomputation, non sequitur, mis-statement, mis-report, mumpsimus, mistake, miss, fault, blunder, quiproquo, cross purposes, oversight, misprint, erratum, corrigendum, slip, blot, flaw, loose thread, trip, stumble, botchery, slip of the tongue, slip of the lip, Freudian slip, slip of the pen, lapsus linguae, clerical error, bull, haplography, illusion, delusion, snare, false impression, false idea, bubble, self-decit, self-deception, mists of error, heresy, hallucination, false light, dream, fable, bias, misleading, erroneous, untrue, false, devoid of truth, fallacious, apocryphal, unreal, ungrounded, groundless, unsubstantial, heretical, unsound, illogical, inexact, unexact inaccurate, incorrect, indefinite, illusive, illusory, delusive, mock, ideal, spurious, deceitful, perverted, controvertible, unsustainable, unauthenticated, untrustworthy, exploded, refuted, discarded, in error, under an error, mistaken, tripping, out, out in one's reckoning, aberrant, beside the mark, wide of the mark, wide of the truth, way off, far off, astray, on a false scent, on the wrong scent, in the wrong box, outside the ballpark, at cross purposes, all in the wrong, all out, more or less, errare est humanum, mentis gratissimus error, on the dubious waves of error tost, to err is human, to forgive divine, you lie -- under a mistake.