Logical Fallacies

A fallacy is an error of reasoning based on faulty use of evidence or incorrect inference (an interpretation of the facts).

Inductive fallacies result from the wrong use of evidence.
Deductive fallacies result from a failure to follow the logic of a series of statements.

Some Common Fallacies

• Hasty Generalization:
  Drawing conclusion on the basis of insufficient evidence. A prejudice is literally a judgement made before the facts are in.

• Faulty use of Authority:
  The attempt to bolster claims by citing the opinions of experts without evaluation and comparison of credentials and claims.

• Post Hoc or Doubtful Cause:
  Post hoc, ergo prompter hoc means, "after this, therefore because of this." The arguer infers that because one event follows another, the first event must be the cause of the second event. Proximity of events or conditions does not guarantee a causal relationship.

• Ad populum:
  "To the people"; "most people agree that"; playing on the prejudices of the audience.

• Non sequitur
  "It does not follow." Using irrelevant proof to support a claim.

• Ad hominem:
  "Against the man"; attacking the arguer rather than the argument; discrediting an argument by trashing the person making it.

• Appeal to tradition:
  a proposal that something should continue because it has traditonally existed or been done that way.

• Faulty emotional appeals:
  basing an argument on feelings, especially pity or fear, often to draw attention away from the real issue/s or to conceal another purpose.
  • Appeal to pity:
    

  • Appeal to fear:

• Tu quoque:
  "Thou also."; It's o.k. to do it, because others do.

• Slippery slope:
  predicting without justification that one step in a process will lead unavoidably to a second, generally undesirable step.

• False analogy:
  assuming without sufficient proof that if objects or processes are similar in some ways, then they are similar in other ways as well. Many analogies are merely descriptive and do not offer proof of the connection between two things being compared.
  • Fallacy of the Whole:
    "What is true of the parts is true of the whole."

  • Fallacy of Division:
    "What is true of the whole must be true of the individual parts."

• Two wrongs make a right:
  diverting attention from the issue by introducing a new point...by responding to an accusation with a counter-accusation that makes no attempt to refute the first accusation.

• Fallacy of false dichotomy or false dilemma:
  Simplifying a complex problem into an either/or dichotomy.

• Shifting the burden of proof:
  challenging the audience to disprove the argument.

• Begging the question:
  restating the claim as evidence for the claim. If the writer makes a statement that assumes that the very question being argued has already been proven, the writer is begging the question. Circular reasoning is an extreme example of begging the question. "Women should not be permitted to join men's clubs because the clubs are for men only."

• Straw man fallacy: associating a claim with another claim, and then arguing against the second claim. This fallacy consists of an attack on a view similar to but not the same as the one your opponent holds. It is a familiar diversionary tactic. The name probably derives from an old game in which a straw man was set up to divert attention from the real target that a contestant was to knock down..

Terms glossed from:

Rottenberg, Annette T. Elements of Argument. 4th ed. Boston: Bedford, 1994.

Hollihan, Thomas A., and Kevin T. Baaske. Arguments and Arguing: The Products and Process of Human Decision Making. New York: St. Martin's, 1994.