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From Stephen's Guide (9)
Causal Fallacies
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It is common for arguments to conclude that one thing causes another. But the
relation between cause and effect is a complex one. It is easy to make a mistake.
In general, we say that a cause C is the cause of an effect E if and only if:
(i) Generally, if C occurs, then E will occur, and
(ii) Generally, if C does not occur, then E will not occur ether.
We say "generally" because there are always exceptions. For example:
We say that striking the match causes the match to light, because:
(i) Generally, when the match is struck, it lights (except when the match
is dunked in water), and
(ii) Generally, when the match is not struck, it does not light (except when
it is lit with a blowtorch).
Many writers also require that a causal statement be supported with a natural law.
For example, the statement that "striking the match causes it to light" is supported
by the principle that "friction produces heat, and heat produces fire".
The following are causal fallacies:
1. Coincidental Correlation
(post hoc ergo propter hoc )
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Definition:
The name in Latin means "after this therefore because of this".
This describes the fallacy. An author commits the fallacy when
it is assumed that because one thing follows another that the
one thing was caused by the other.
Examples:
(i) Immigration to Alberta from Ontario increased. Soon
after, the welfare rolls increased. Therefore, the increased
immigration caused the increased welfare rolls.
(ii) I took EZ-No-Cold, and two days later, my cold
disappeared.
Proof:
Show that the correlation is coincidental by showing that: (i)
the effect would have occurred even if the cause did not
occur, or (ii) that the effect was caused by something other
than the suggested cause.
2. Joint Effect
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Definition:
One thing is held to cause another when in fact both are the
effect of a single underlying cause. This fallacy is often
understood as a special case of post hoc ergo prompter hoc.
Examples:
(i) We are experiencing high unemployment which s being
caused by a low consumer demand. (In fact, both may be
caused by high interest rates.)
(ii) You have a fever and this is causing you to break out in
spots. (In fact, both symptoms are caused by the measles.)
Proof:
Identify the two effects and show that they are caused by the
same underlying cause. It is necessary to describe the
underlying cause and prove that it causes each symptom
3. Genuine but Insignificant Cause
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Definition:
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 the Tory
government because you voted Reform, for your vote had as
much weight as any other vote, and hence is equally a part of
the cause.
Examples:
(i) Smoking is causing air pollution in Edmonton. (True, but
the effect of smoking is insignificant compared to the effect
of auto exhaust.)
(ii) By leaving your oven on overnight you are contributing
to global warming.
Proof:
Identify the much more significant cause.
4. Genuine but Insignificant Cause
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Definition:
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 the Tory
government because you voted Reform, for your vote had as
much weight as any other vote, and hence is equally a part of
the cause.
Examples:
(i) Smoking is causing air pollution in Edmonton. (True, but
the effect of smoking is insignificant compared to the effect
of auto exhaust.)
(ii) By leaving your oven on overnight you are contributing
to global warming.
Proof:
Identify the much more significant cause.
5. Wrong Direction
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Definition:
The relation between cause and effect is reversed.
Examples:
(i) Cancer causes smoking.
(ii) The increase in AIDS was caused by more sex education.
(In fact, the increase in sex education was caused by the
spread of AIDS.)
Proof:
Give a causal argument showing that the relation between
cause and effect has been reversed.
6. Complex Cause
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Definition:
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:
(i) 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.)
(ii) The Challenger explosion was caused by the cold
weather. (True, however, it would not have occurred had the
O-rings been properly constructed.)
(iii) People are in fear because of increased crime. (True, but
this has lead people to break the law as a consequence of
their fear, which increases crime even more.)
Proof:
Show that all of the causes, and not just the one mentioned,
are required to produce the effect.
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发表于 2003-6-26 15:45:00
