What are Fallacies?

Fallacies are errors in reasoning. If it is done intentionally to deceive an opponent, it is called sophism or sophistry. If it is done unintentionally, it is called paralogism.

It may be classified in to the following:

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Formal or logical fallacies

Violations of the rules of logic

Fallacies of definition

  • Fallacy of too wide definition (e.g., Man is an animal)
  • Fallacy of too narrow definition (e.g., Man is an irritable rational animal)
  • Fallacy of redundant definition (e.g., Man is a rational animal capable of learning logic)
  • Fallacy of accidental definition (e.g., Man is a rational animal who can bake a cake)
  • Fallacy of circular definition (e.g., Man is a human being)
  • Fallacy of obscure definition (e.g., A net is a reticulated fabric, decussated to regular intervals, with intestines and intersections)
  • Fallacy of figurative definition (e.g., Reading is a wide open door to greater intellectual growth)
  • Fallacy of negative definition (e.g., A male is a man who is not a female)

Fallacies of division

  • Fallacy of cross division – there has to be only one rule of division at a time
  • Fallacy of too wide division (e.g., Divide man into red, black, brown, yellow, white, red, blue)
  • Fallacy of too narrow division (e.g., Triangle into equilateral and isosceles)
  • Fallacy of remote division – skipping logical hierarchies of division

Fallacies of eduction

  • Fallacy of incorrect conversion
  • Fallacy of incorrect obversion

Fallacies in categorical syllogisms

  • Fallacy of four terms
  • Fallacy of ambiguous middle – the middle term has an ambiguous meaning
  • Fallacy of negative premises
  • Fallacy of undistributed middle – the middle term must be universal at least once in a syllogism
  • Fallacy of particular premises
  • Fallacy of illicit major – when a particular minor term becomes universal
  • Fallacy of illicit minor – when a particular major term becomes universal
  • The IEO fallacy

Fallacies in hypothetical syllogisms

  • Fallacy of rejecting the antecedent

                If Mike marries Mary, she will be happy               
But he will not marry Mary               
Ergo, Mary will not be happy

  • Fallacy of accepting the consequent

                If I eat spinach, I will have huge muscles
But I will eat spinach
Therefore, I will have huge muscles

  • Fallacy of sublate posit / tollendo ponens

                Today is either Monday or Tuesday
But it is not Monday
Therefore, it is Tuesday

Informal or material fallacies

It arises from confusion with the use of terms, wrong assumption of facts, and evading the issue under consideration

Fallacies in language

  • Fallacy of equivocation – a key term is used in a ambiguous way, the term used in one way in the first part of the argument and then used in another way in the second part of the argument.
  • Fallacy of amphibology – ambiguous use of a phrase, not a single word (e.g., The lost dog of the lady with the long tail)
  • Fallacy of accent or prosody – false emphasis in speech
  • Fallacy of figure of speech
  • Fallacy of composition – taking in collectively what should be taken individually
  • Fallacy of division – taking in individually what must be taken collectively
  • Fallacy of accident – when the accidental is confused with the essential (e.g., Filipinos are brown, but brown is a color, therefore Filipino is a color)
  • Fallacy of pretended or false clause – assigning an effect to a false cause
  • Fallacy of hasty generalization
  • Fallacy of irrelevant premises – when a conclusion is derived from irrelevant premises

Fallacies of presumption

when the truth is assumed without evidence

Fallacy of begging the question (petition principii) – the truth is assumed whilst it is yet to be proved

fallacy of assumptio non-probata – when one assumes the truth of an unproved premise

Fallacy of circulus in probando – circular argument

Fallacy of evading the question – may be one or more of the following: (1) proving what is not supposed to be proved, (2) not proving what is supposed to be proved, (2) disproving what has not been asserted, and (4) proving something beside the question 

  • Argumentum ad hominem (argument to the man) – character assassination, attacking below the belt, mud slinging, name calling (e.g, “my opponent is a communist for even thinking about socialized healthcare”)
  • Argumentum ad populum (argument to the people) – trying to prove an argument by showing public agreeing with you.
  • Argumentum ad numerum (argument or appeal to numbers) – trying to prove an argument using numbers or how many people agree with you. Having many people believe something is true doesn’t make it the truth (e.g., 9 out of 10 dentist trust toothpaste x, therefore toothpaste x can strengthen my teeth)
  • Argumentum ad misericordiam (argument to the sympathy) – playing on emotions or trying to sway an argument using emotional pleas (e.g., Will somebody think of the children?!)
  • Argumentum ad crumemam (argument to the money) – appeals to the sense of greed
  • Argumentum ad verecundiam (argument to the traditions or customs) – the sanctity of tradition justifies the proposition
  • Argumentum ad ignorantium – an argument is true or false because people are ignorant about it
  • Argumentum ad auctoritatem (argument to the authority) – citing someone who agrees to your argument even though that person has little expertise on the subject or area.

Fallacy of complex question – asking questions that already assumes an answer (e.g., have you finally given up our bad habits?)

Fallacy of non-sequitur – “it does not follow” (e.g., Ms. X is very beautiful, therefore she must be given a high grade)

Other Articles:

Logic as a Branch of Philosophy
What is Ethics?

Metaphysics as a Branch of Philosophy