Also Known as: Questionable Cause
This fallacy has the following general structure:
- A and B are regularly connected (but no third, common cause is looked for).
- Therefore A is the cause of B.
This fallacy is committed when it is concluded that one thing causes
another simply because they are regularly associated. More formally,
this fallacy is committed when it is concluded that A is the cause of B
simply because A and B are regularly connected. Further, the causal
conclusion is drawn without considering the possibility that a third
factor might be the cause of both A and B.
In many cases, the fallacy is quite evident. For example, if a person
claimed that a person's sneezing was caused by her watery eyes and he
simply ignored the fact that the woman was standing in a hay field, he
would have fallen prey to the fallacy of ignoring a common cause. In
this case, it would be reasonable to conclude that the woman's sneezing
and watering eyes was caused by an allergic reaction of some kind. In
other cases, it is not as evident that the fallacy is being comitted.
For example, a doctor might find a large amount of bacteria in one of
her patients and conclude that the bacteria are the cause of the
patient's illness. However, it might turn out that the bacteria are
actually harmless and that a virus is weakening the person, Thus, the
viruses would be the actual cause of the illness and growth of the
bacteria (the viruses would weaken the ability of the person's body to
resist the growth of the bacteria).
As noted in the discussion of other causal fallacies, causality is a
rather difficult matter. However, it is possible to avoid this fallacy
by taking due care. In the case of Ignoring a Common Cause, the key to
avoiding this fallacy is to be careful to check for other factors that
might be the actual cause of both the suspected cause and the suspected
effect. If a person fails to check for the possibility of a common
cause, then they will commit this fallacy. Thus, it is always a good
idea to always ask "could there be a third factor that is actually
causing both A and B?"
- One day Bill wakes up with a fever. A few hours later he finds
red spots on his skin. he concludes that the fever must have caused the
red spots. His friend insists that the spots and the fever are caused by
some microbe. Bill laughs at this and insists that if he spends the day
in a tub of cold water his spots will go away.
- Over the course of several weeks the needles from the pine trees
along the Wombat river fell into the water. Shortly thereafter, many
dead fish washed up on the river banks. When the EPA investigated, the
owners of the Wombat River Chemical Company claimed that is it was
obvious that the pine needles had killed the fish. Many local
environmentalists claimed that the chemical plant's toxic wastes caused
both the trees and the fish to die and that the pine needles had no real
effect on the fish.
- A thunderstorm wakes Joe up in the middle of the night. He goes
downstairs to get some milk to help him get back to sleep. On the way to
the refrigerator, he notices that the barometer has fallen a great deal.
Joe concludes that the storm caused the barometer to fall. In the
morning he tells his wife about his conclusion. She tells him that it
was a drop in atmospheric pressure that caused the barometer to drop and
the storm.
[
Previous
|
Index
|
Next
]
© The Nizkor Project, 1991-2008
