Logical Fallacies

In a valid logical argument:

  • If ALL of the premises are true, then the conclusion must be true.
  • If ANY of the premises are false, then a valid logical argument may still lead to a false conclusion.

An invalid or unsound argument:

  • Does not necessarily prove the conclusion false, just that it is not necessarily true.
  • It is  possible that an argument that uses incorrect information or faulty logic can still result in a conclusion that happens to be true.

A logical fallacy is a reasoning flaw.

Not only must the factual data that is part of a premise be valid, but the reasoning used to employ those facts must not contain reasoning flaws – logical fallacies.  For those unfamiliar with logical fallacies, below are some common logical fallacies taken from Thou Shalt Not Commit Logical Fallacies which is a great reference source.

False Cause – The presumption that a real or perceived relationship between things means that one is the cause of the other.

Texas Sharpshooter – Cherry-picking a data cluster to suit the argument or finding a pattern to fit a presumption.

Appeal to Authority – Saying that because an authority says something, it must therefore be true.

Appeal to Emotion – Attempted manipulation of an emotional response in place of a valid or compelling argument.

Strawman – Misrepresenting someone’s argument to make it easier to attack.

Ad Hominem – Attacking an opponent’s character or personal traits in an attempt to undermine their argument.

Loaded Question – Asking a question that has a presumption built into it so that it can’t be answered without appearing guilty.

Ambiguity – Use of a double meaning or ambiguity of language to mislead or misrepresent the truth.

Bandwagon – Appeal to popularity as an attempted form of validation.

Black-or-White – Presenting two alternatives as the only possibilities when more possibilities exist.

Anecdotal – Using a personal experience or isolated example instead of a sound argument or compelling evidence.

Slippery Slope – Asserting that if we allow A to happen, then Z will eventually happen too, therefore A should not happen.

The Rules of Engagement

Logical fallacies can be used unintentionally or intentionally.  For example:

  • Politicians do it to get support and votes.
  • The media does it to get viewers, readers, etc. in order to sell ad space.
  • Advertisers do it to sell their products.
  • Individuals do it to convince others of their opinions.

For the purposes of Runaway Logic, we should endeavor to avoid logical fallacies.


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