10comsof logicI want us to consider a range of fallacies and the motivations of those that make fallacious knowledge claims. When you are researching your issues and listing arguments for and against certain viewpoints, it is important to be able to critically appraise lines of argument. Usually this will be through a study of the language used by protagonists.

Find some written or spoken evidence of the views you have collected over the last week and study the language used and try to spot fallacies.

This video may help….

An extensive info-graphic of rhetorical and logical fallacies

Common Fallacies

A good TOK site on fallacies

Good introductory videos on critical thinking and fallacies

These descriptions of fallacies (left column) do not match the examples in the right coloum – please unscramble and match them correctly.

Ad Hominem: This is Latin for “attack the man” and is an irrelevant attack on the person or group being debated rather than addressing his/her/its argument.  “There is no compelling evidence that UFOs are not visiting the Earth; therefore, UFOs must exist” and “people have been trying for centuries to prove that God exists but no one has yet been able to prove it; therefore, God does not exist.”
Appeal to Authority:  This is an improper yielding to an opinion by someone or something that is in a position of power or an expert who is out of his/her area of expertise. “It may be hard for you to believe that God is merciful and at the same time can condemn non-believers to eternal punishment because you do not understand the Biblical doctrines of original sin and free will” and “my client may have broken the law by stealing a television, but he is poor and it is excusable.
Appeal to Ignorance: This is the claim that whatever has not been proved false must be true and vice versa. Essentially, it is the idea that absence of evidence is not absence of evidence The Bible says that the Earth was created in 6 days; therefore, it is correct despite the contrary evidence” and “we should abolish the death penalty because many respected people, such as actress Ima Awesome, have publicly stated their opposition to it.
Special Pleading: This is an attempt to rescue a proposition that is in deep logical and/or rhetorical trouble.  “I know of a 40-year-old who looks 60 because she takes contraceptives” and “the President lowered taxes and then the rate of violent crime went up; therefore, he is responsible for the rise in crime.”
Observational Selection: This is when only favourable circumstances are given. The philosopher Francis Bacon described it as counting the hits and forgetting the misses. “a state boasts of the Presidents it has produced (but is silent on its serial killers)” and “a boxer boasts of how many fights that he has won (but does not mention the loses).”
Post hoc (also called the questionable cause): This is Latin for “it happened after, so it was caused by” and it is questionable cause when there is not sufficient evidence to support it. “Scientists believe in the process of Evolution because they deny the existence of God and as such believe that all living things simply fell together by pure chance” and “conservatives want to change welfare benefits because they care more about big business and money than they do for poor people.”
Excluded Middle (also called the either/or fallacy): This is when only the two extremes are considered in a continuum of intermediate possibilities. “Either you love your country music or you hate it” and “If you’re not part of the solution, you’re part of the problem.”
Slippery Slope (related to excluded middle but not as subtle): This is when it is suggested that that if one undesirable action is allowed to occur, then it will inevitably lead to another similar but less desirable action without sufficient evidence “John Smith’s argument for the existence of Israel is irrelevant because he is bald and fat” and “embryonic stem cell research destroys human life and anyone that supports it is like a Nazi because they liked to destroy life too.”
Straw Man: This is when one sets up an unrelated and easily refuted objection to an argument or the opponents position is misinterpreted to make it easier to attack. Animal experimentation reduces our respect for life which means that we become more tolerant of violent acts like war and murder leading to the end of civilization” and “if compulsory prayer is removed from the public school system then all religious expressions in all aspects of life will someday be outlawed.”

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