Logical fallacies

Updated 25 March 2015

What is a logical fallacy?

Logical fallacies are essentially errors of reasoning in making an argument. When logically fallacious arguments are used, usually based on bad reasoning to support a position (or to try to convince someone to adopt the same position), it is considered a fallacy.  

This means that an argument that uses a logical fallacy shouldn’t hold up to those using logic and reason as the source of decision making. Of course, it generally doesn’t stop people, specifically those pushing pseudoscience or an anti-science point of view, from using them or being swayed by them.

There are two forms of a logical fallacy:

  • Formal–These logical fallacies are those fallacies that violate a particular rule of logic. They almost always include non sequitur logic, that is, the conclusion is not connected to the argument.
  • Informal– arguments that, while not violating logic rules, are invalid because of the content of their argument. Informal fallacies are often characterised by the fact that there is a disconnect of some kind between their premises and conclusions.

Deciding between formal and informal logical fallacies is interesting for logic geeks, but I didn’t want to spend time separating between the two. The net effect of either type of logical fallacy is the same–the arguments can be dismissed.

Below is a list of the most common fallacies that are used by those who push pseudoscience or deny science:

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  • http://beginingsinwriting.wordpress.com/ R.w. Foster

    Is there a “Misuse of the Precautionary Principle” fallacy? That’s one the anti-GMO crowd likes to use on occasion.

    How about “Not Understanding Climate Models,” one?

    • http://www.skepticalraptor.com/skepticalraptorblog.php Skeptical Raptor

      I’m actually adding the Precautionary Principle. It’s not exactly a logical fallacy, but close enough.

      I think climate change is too specific for this page. I need to write a bit more about global warming, and I’ve got to find something that is good and snarky.

      • http://beginingsinwriting.wordpress.com/ R.w. Foster

        I look forward to it. Snarky or not, you deliver with great science.

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