Rational Thinking & Creative Ideas
Erroneous Reasoning: Fallacies
1. Fallacies are simply mistakes or defects that occur in arguments. They are incorrect inferences. Fallacious arguments may superficially be persuasive, but logically incorrect. Fallacies can be committed in many ways, but usually they involve either a mistake in reasoning or creation of some illusion that make a bad argument appear good. Understanding fallacies and knowing why some inferences are incorrect could help us to improve our way of rational thinking and reasoning.
• Two kinds of fallacies: formal and informal. Formal fallacies occur when we misapply a valid rule or form of inference or else follow a rule which is invalid. Informal fallacies are any errors in reasoning not related to the form (but content) of the arguments.
2. Informal fallacies: Some fallacies that people frequently committed are introduced and illustrated:
(i)Hasty generalization draws a conclusion about a class based on too few or atypical cases. We commit this fallacy when move carelessly and quickly from few particular cases to a generalization.
Example 3: I know that John Lee is bald but rich. Therefore, all bald persons are rich.
• Only one particular case of being bald and rich is far from enough to support the conclusion that all bald persons are rich. The conclusion is likely to be false. So, it is a fallacy of hasty generalization.
Example 4: Last Friday, I broke my arm. The Friday before that I failed the driving test. Oh, God, bad things always happen to me on Fridays.
• The probability of the conclusion is extremely low. Two bad things on two Fridays are hardly adequate to support a general conclusion about all Fridays. It is thus a hasty generalization.
(ii)Accident is the reverse of hasty generalization. When we apply a generalization to individual particular cases that it does not properly govern, we commit the fallacy of accident. In morality, rules or principles that are sound in general sometimes have very special exceptions. We have the moral rule that “we should not lie”. In some special circumstances, this rule may not be applicable, say, lying to a dying friend and comfort her that she is going to recover from illness.
Example 5: Of course, Ah Ming can play his guitar with his band at mid-night. Our freedom of speech and expression is a guaranteed right. • We have the right of speech and expression. But we cannot exercise our right at any time as we wish. If in exercising our right, we violate other person’s right or harm others, it is improper for us to do so. Ah Ming has the right, but it is improper for him to play guitar with his band at mid-night, making a lot of noises and disturbing others.
(iii)False cause: Any reasoning that relies on treating as the cause of some thing or event what is not genuinely its cause must be seriously mistaken. Fallacy of false cause mistakes temporal succession for causal sequence. That is, one assumes that because two events are associated in time, one must have caused the other.
Example 6: John Dum, a middle-aged man, raped and killed an old lady after seeing a class-III film. “Had it not been for pornography,” a conservative legislator claimed, “John Dum would not have committed the crime.”
• Two events happened one after the other: “John Dum watched a pornographic film”, “he committed the crime”. But the legislator jumped to the conclusion that these two events have causal relation. Though two events happened one after the other, they might not have causal relation.
Example 7: David Lee is a champion runner. He has been living in Tuen Mun since he is born. Hence, living in Tuen Mun helps to make David Lee a champion runner.
• We have a correlation of two events, “living in Tuen Mun” and “being a champion runner”, but there is no evidence to indicate that the correlation is causal. Given the premises, the probability of the conclusion is quite low. The...
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