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Logical Fallacies

brain gears

To help develop my mental toolkit, I have been taking a closer look at Logical Fallacies –  poor arguments of logic, or misconceptions that result from incorrect reasoning.

There are dozens of these, often with grand sounding Latin names or wordy definitions.

Two useful extra sources are: and

False Cause: also known as Magical Thinking, Ignoring a Common Cause, or PostHoc, Ergo Propter Hoc (After this, therefore because of this). An example would be, “Severe weather incidents have increased because more countries are allowing same sex marriage”out out

Straw Man: also known as Argumentum Ex Culo (argument pulled from ‘thin air’). An opponent will deliberately misrepresent someone’s position to try to weaken it. For example, “Evolution is a stupid theory. A crocodile cannot evolve into a duck!”

Appeal to Authority: Argumentum Ad Verecundiam (argument from respect). Someone famous or powerful believes it, so it must be true. “Andrew Strauss, the Ashes series winning captain, wears a Power Balance band, so it must improve my cricket skills”.

Slippery Slope: also known as Reductio ad Absurdum. This involves a general assertion that if we allow A to happen, then Z will follow, so stop A happening. For example, ”If we allow same sex marriage, then next we’ll have people marrying animals or their children” (Norman Tebbit actually said “It would lift my worries about inheritance tax because maybe I’d be allowed to marry my son!”

At the Person: also known as Ad Hominem. Person A claims X, but there is something objectionable about them, so X is false. A special version of this is Reductio ad Hitlerum “Hitler was in favour of euthanasia, therefore, euthanasia is wrong.” (he was also a painter, vegetarian and Roman Catholic, so go figure). See also Godwin’s Law and internet trolls!Godwin

Appeal to Ancient Wisdom: This is of the form: Culture A said thing X: Culture A lived a long time ago.Therefore X is true. This fallacy is often cited by a number of alternative medicine supporters and creationists. Such ancient practices include blood-letting, trepanning, human sacrifice, Flat Earth, herbal medicine and acupuncture.

good point

These examples have been used by many Republicans, some Creationalists,promoters of Power Balance bands and Kinesio Tape, anti-marriage equality groups, woo merchants and many more.


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