logical fallacy

/ˌlɑdʒəkəl ˌfæləsi/

Other forms: logical fallacies

When you make an argument based on reasoning that's just plain wrong, it's a logical fallacy. If you're on the debate team, you've probably learned the many types of logical fallacy — like a "strawman argument," which means arguing against a position your opponent doesn't actually hold.

A fallacy is a mistaken belief or argument, and a logical fallacy arises specifically out of an error in logic. Walking to school this morning, you saw someone riding a horse down the sidewalk; if you feel sick to your stomach when you get to school, deducing that horses make you ill would be an obvious logical fallacy. Another logical fallacy would be believing the earth is flat because you saw it on the internet.

Definitions of logical fallacy

1. noun

   a fallacy in logical argumentation
   types:

   hysteron proteron

   the logical fallacy of using as a true premise a proposition that is yet to be proved

   ignoratio elenchi

   the logical fallacy of supposing that an argument proving an irrelevant point has proved the point at issue

   petitio, petitio principii

   the logical fallacy of assuming the conclusion in the premises; begging the question

   post hoc, post hoc ergo propter hoc

   the logical fallacy of believing that temporal succession implies a causal relation

   type of:

   fallacy, false belief

   a misconception resulting from incorrect reasoning