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A fallacy (Lat. fallacia, from fallax, meaning deceitful, or fallere, to deceive) may be defined as a statement or argument that leads one to a false conclusion because of a misconception of the meaning of the words used or a flaw in the reasoning involved. Some terms often used as synonyms of fallacy have different shades of meaning. Thus, a sophism (Gr. σοφός, wise) is a false argument offered with deliberate intent to deceive, a sophist being one who would rather appear to be wise than be wise, i.e., be a trickster (see sophists). A paralogism (Gr. παρά, contrary to, and λόγος, reason) is an unintentional violation of the rules of logic. A paradox (Gr. παρά, contrary to, and δόξα, opinion) is a statement that sounds absurd or contradictory, but yet may be true in fact, i.e., "I die to live."

Classification. There is no strict agreement among logicians on the classification of fallacies. Some distinguish only two basic types, namely, those "in diction" and those "extra diction." Modern writers usually amplify the list with new titles that expand or, in some instances, merely duplicate, the basic concepts. The following outline reflects the more recent methods of classifying fallacies:

  • I. Fallacies of induction
  • A. Insufficient observation
  • B. Unwarranted generalization
  • C. False analogy
  • II. Fallacies of deduction
  • A. Formal
  • 1. In the proposition
  • 2. In the syllogism
  • a. Illicit premises
  • b. Undistributed middle
  • c. Extended conclusion
  • B. Material
  • 1. In diction
  • 2. Extra diction

Regarding inductive fallacies, it is obvious that inadequate observation of particulars cannot lead to a valid generalization. Only after a sufficient number of cases have been carefully checked and rechecked can a safe conclusion be drawn. Again, analogy is good for comparison, but becomes illicit when used to imply identity in nature or characteristics. Children, for example, are as frisky as lambs, but to conclude to an identification of all other characteristics would be unwarranted.

Among deductive fallacies, formal fallacies (paralogisms) arise from violations of the rules of logic regulating the drawing of inferences from propositions and of conclusions from premises in syllogisms. In the case of the proposition, fallacies may result from improper obversion, conversion, or opposition, for example, converting "All men are mortal" to "All mortals are men." These are called fallacies of simple inspection. In the case of the syllogism, formal fallacy may result from violation of any of the rules of syllogistic reasoning. Thus, the syllogism "Man is rational; a woman is not a man; therefore, a woman is not rational," violates the rule that demands only three terms. Some violationssuch as having two negative premises, or having two particular premises, or concluding universally from a particular premise or affirmatively from a negative one, or introducing the middle term into the conclusionare obvious. Others require an expert knowledge of formal logic to detect them.

Fallacies are divided materially into those "in diction" (fallacies of language that arise from an abuse of words) and those "extra diction" (fallacies apart from language that arise from an abuse of reasoning about things). These can be further divided and subdivided in various ways, of which the following are representative.

  • I. Fallacies in diction.
  • A. Equivocationone word mistaken for another. "He turned the page. " (Boy or book?)
  • B. Amphibologydouble-meaning sentence. "He shot the man with his gun." (Whose?)
  • C. Compositionattributing to the whole what is true only of the part. "A is a fine ballplayer; B is a fine ballplayer; C is a fine ballplayer. Ergo, this is a fine team."
  • D. Divisionattributing to the part what is true only of the whole. "The straw that broke the camel's back."
  • E. Metaphortaking a figure of speech literally or stretching it unduly. "He was as hungry as a horse, so he ate a bucket of oats."
  • F. Accentdifferent stress, tone, or gesture giving a different meaning to a word. "Minute or minute steak?" "Was the priest in -censed, or in-censed ?"
  • II. Fallacies extra diction.
  • A. Accidentpresenting as true in the definite particular what is only generally true. "Americans are a generous people; I am an American; therefore, I am generous."
  • B. False absoluteassuming as always true what is true only in its proper field or circumstance. "'Thou shalt not kill.' Therefore, wars are forbidden."
  • C. Pretended causepost hoc, ergo propter hoc; a prior event is cited as cause of a subsequent one. "After the U.S. adopted prohibition, the nation prospered."
  • D. Evading the issueignoratio elenchi. "Have you ever been arrested?" "Sir, how dare you ask me that?" This fallacy has many forms, the principal ones of which are:
  • 1. Argumentum ad hominem argument against the person, not the issue.
  • 2. Argumentum ad populum plea based on the arousal of passion and prejudice in a crowd.
  • 3. Argumentum ad verecundiam (sense of shame)embarrassing a speaker by quoting a great name against him. "Einstein would not agree."
  • 4. Argumentum ad misericordiam (mercyplea)"But, Judge, he is of your faith (race)."
  • 5. Argumentum ad ignorantiam taking advantage of one's ignorance. "It won't hurt, child."
  • 6. Argumentum ad baculum (the big stick) threatening an opponent, making him concede through fear. "This, or else!"
  • E. Begging the question (petitio principii )more than a mere evasion, actually negation or contradiction of the issue. "A monarchy is the best form of government, because it gives everyone a voice." This fallacy is said to have four forms:
  • 1. Flat contradiction"I do not exist."
  • 2. Hysteron-proteron a purely empty, negative response taking for granted what needs to be proved. "Women are incomprehensibleno man can say he understands them."
  • 3. Tautologya mere repetition. "A circle is a line that circles around."
  • 4. Vicious circletrying to prove statement A by reason of B, whose validity depends on A. "A soul is simple because it is nondimensional, and it is nondimensional because it is simple."
  • F. The complex questiona "loaded" query that cannot be answered by a simple yes or no. "Have you stopped taking graft?"

Evaluation. These are the most commonly cited fallacies. Their true number, however, is incalculable because some obscurity is to be found in every action and utterance of man, the fallible creature. logic tries to discover the true intent and to detect misconceptions, but only He who is "the searcher of heart and soul" (Ps 7.10) can avoid all fallacies.

truth itself is the primary objective of the intellect, just as the good is the goal of the will. Man strives for the truth in many waysby listening, reading, observing, meditating, and praying. He attains some truths, yet always imperfectly by reason of his first fallacy, the Fall. When he tries to enunciate the truth to others, he encounters the difficulty of choosing the proper, unequivocal word. The hearer, handicapped by his own imperfections, which are sometimes accentuated by prejudice or ill-will, does not always receive the exact meaning intended.

But this fecundity of fallacies, so evident in human affairs, should not make one cynical. In substance, if not in all its details and if not immediately, truth is possible of attainment. Civil courts, historical research, scientific experiments, scriptural exegesis, and philosophical and theological investigationeven such things as panel discussions and public debatesall seek to ferret out the truth. Thus avoidance of fallacy becomes the grand adventure of man's rationality. Truth presents a difficult challenge when compared to the ease of error, but it also offers an exceedingly great reward.

See Also: falsity; antinomy; argumentation.

Bibliography: s. j. hartman, Fundamentals of Logic (St. Louis 1949). r. houde and j. j. fischer, Handbook of Logic (Dubuque 1954). j. a. oesterle, Logic: The Art of Defining and Reasoning (2d ed. Englewood Cliffs, N.J. 1963).

[p. c. perrotta]

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fal·la·cy / ˈfaləsē/ • n. (pl. -cies) a mistaken belief, esp. one based on unsound argument. ∎  Logic a failure in reasoning that renders an argument invalid. ∎  faulty reasoning; misleading or unsound argument: the potential for fallacy which lies behind the notion of self-esteem. DERIVATIVES: fal·la·cious / fəˈlāshəs/ adj. fal·la·cious·ness / fəˈlāshəsnəs/ n.

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FALLACY. In general usage, a false and often deceitful idea; in logic, a line of reasoning (also known as a paralogism) that may seem valid but is not. Fallacies of discourse were first described in Greek and Latin, and many therefore retain their classical names, either uniquely or alongside a vernacular label. They include: (1) Argumentum ad baculum [Latin: argument backed by a stick]. Resorting to threat in order to have a point accepted. (2) Argumentum ad hominem [Latin: argument directed at the person]. Often called an ad hominem argument or an ad hominem attack. Seeking to disprove a point by attacking the people making that point, either in terms of their character or by referring to their personal circumstances as an explanation of why a position has been adopted. (3) Argumentum ad populum [Latin: argument directed at the people]. An appeal to popular opinion, bias, and inclination. (4) Non sequitur [Latin: it does not follow]. A statement in which the premisses of an argument do not lead to the conclusion provided. (5) Post hoc ergo propter hoc [Latin: after this therefore because of this]. Asserting that because A came before B, A caused B.

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fallacy deception XV; logical flaw, delusive notion XVI; delusive nature XVIII. — L. fallācia, f. fallāx, fallāc-, f. fallere deceive.
So fallacious XVI. — (O)F. fallacieux. See -ACY, -ACIOUS.