Beliefs & fallacies
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- Post Hoc: because one thing follows another, it is held to cause the other
- Joint Effect: the occurrences of cause and effect are actually both consequences of a joint cause
- Insignificant: the purported cause is insignificant compared to others
- Wrong Direction: alleging a cause to be a consequence of its actual effect (the direction between cause and effect is reversed)
- Complex Cause: the cause identified is actually only part of the entire cause
The following are causal fallacies:
It is common for us to conclude that one thing causes another. But the true relation between cause and effect can be complex; it is easy to make a mistake.
For example, we say that striking a match causes the match to light. But, of course, this is an oversimplification: What about a wet match? ..a centuries-old match? ..a wet surface? ..a damaged surface? ..a broken match? ..and on and on....
Learn to temper your statements with words like, "Usually," "Commonly," "Customarily," "Typically," "There is a tendency for," "Most of the time," etc. Learn to discuss variability and mention exceptions when you're providing advice. You'll avoid plenty problems later on.
- 1. Coincidental Correlation (post hoc ergo propter hoc):
- The name in Latin means “after this therefore because of this.” An author/speaker commits this fallacy by assuming that because one thing follows another, it must be a consequence of the other.
Examples:
- Immigration to Alberta from Ontario suddenly increases. Soon thereafter, the welfare rolls increase. Therefore, the increase in immigration caused the increase in welfare rolls.
- I took EZ-No-Cold, and two days later my cold disappeared!
Convincing Others: Show that the correlation is coincidental by showing that:
- the effect would have occurred even if the cause hadn't or
- the effect was caused by something else besides the alleged cause.
References: Cedarblom and Paulsen: 237; Copi and Cohen: 101
- 2. Joint Effect:
- One thing is held to cause another when in fact both are the effect of a single underlying cause. This fallacy is usually understood as a special case of post hoc ergo propter hoc.
Examples:
- We are experiencing high unemployment, which is being caused by a low consumer demand. (In fact, both may be caused by high interest rates.)
- You have a fever, and this is causing you to break out in spots. (In fact, both symptoms are caused by the measles.)
Convincing Others: Identify the two effects and show that they are caused by the same underlying cause. It is usually necessary to describe the underlying cause and prove that it causes each symptom.
Reference: Cedarblom and Paulsen: 238
- 3. Genuine but Insignificant Cause:
- The object or event identified as the cause of an effect is a genuine cause, but insignificant when compared to the other causes of that event.
Note that this fallacy does not apply when all other contributing causes are equally insignificant. Thus, it is not a fallacy to say that you helped cause defeat of the Tory government, for example, because you voted Reform, since your vote had as much weight as any other vote and, hence, is equally a part of the cause.
Examples:
- Smoking is causing air pollution in Edmonton. (True, but the effect of smoking is insignificant compared to the effect of auto exhaust.)
- By leaving your oven on overnight you are contributing to global warming.
Convincing Others: Identify the much more significant cause.
References: Cedarblom and Paulsen: 238
- 4. Wrong Direction:
- The relation between cause and effect is reversed.
Examples:
- Cancer causes smoking.
- The increase in AIDS was caused by more sex education. (In fact, the increase in sex education was caused by the spread of AIDS.)
Convincing Others: Give a causal argument showing that the relation between cause and effect has been reversed.
Reference: Cedarblom and Paulsen: 238
- 5. Complex Cause:
- The effect is caused by a number of objects or events, of which the cause identified is only a part. A variation of this is the feedback loop where the effect is itself a part of the cause.
Examples:
- The accident was caused by the poor location of the bush. (True, but it wouldn't have occurred had the driver not been drunk and the pedestrian not been jaywalking.)
- The Challenger explosion was caused by the cold weather. (True, however, it would not have occurred had the O-rings been properly constructed.)
Convincing Others: Show that all of the causes, and not just the one mentioned, are required to produce the effect.
Reference: Cedarblom and Paulsen: 238
Reprinted with permission from Professor Stephen Downes.
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