Logical Fallacies

An argument consists of the point you want to prove (a hypothesis), a set of facts that show beyond a doubt that your theory is correct (supporting evidence), and a conclusion — the only conclusion that can be — drawn from the facts (completeness).

It sounds straightforward, but people rarely can or do take the time to do an exhaustive analysis before presenting an argument. Consequently, people make mistakes, and when they do, we call these mistakes logical fallacies. For your reference, review this short list of common logical fallacies:

Please note: Recognizing a fallacy does not automatically make the argument under scrutiny incorrect or the opposite position correct; it simply means the reasoning needs improvement — there is more work to do.

• ad hominem: Instead of presenting a set of supporting facts, the arguer makes personal attacks on the opposition.
• Appeal to Emotions: The arguer has chosen a sensational set of facts to support her argument or has littered her argument with platitudes and appears more interested in manipulating people's emotions than making a claim.
• Straw Man: The arguer changes the subject and presents an entirely different argument — one that's easy to win.
• Slippery Slope: The arguer presents a chain of outcomes (instead of facts), implying one event leads to another, to the next, until the sky falls. We don't want the sky to fall, so we can't let that first event in the chain happen.
• False Dilemma: The arguer insists the facts lead to only one of two possible conclusions or actions (usually extremes) when other options or interpretations exist.
• Faulty Premise: The arguer does present a set of facts to support his case, but at least one "fact" is incorrect, in dispute, or unproven.
• Biased Argument: The arguer presents a set of facts to support his case, and the argument seems sound, but the arguer ignores evidence to the contrary which would cast doubt on his conclusion.
• Appeal to Authority: The arguer insists some of his evidence must be accepted as fact because an authority or person of influence has endorsed it — but the act of endorsing the data does not make it true or sufficient.
• Hasty Conclusion: The arguer does present a set of proven facts, but these facts are insufficient to draw the conclusion or more than one conclusion can be drawn from the data presented. More evidence is required.
• Red Herring: The arguer has included irrelevant but true facts that are leading away from a correct conclusion. The facts presented are misleading.