Casual falacies
Casual falacies involve cause and effect. 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:
- Generally, if C occurs, then E will occur, and
- Generally, if C does not occur, then E will not occur.
- We say "generally" because there are always exceptions. For example, we say that striking the match causes the match to light, because:
- Generally, when the match is struck, it lights, and
- Generally, when the match is not struck, it does not light.
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".
Post Hoc Ergo Propter Hoc
The name in Latin means "after this therefore because of this". This fallacy occurs when something is assumed to be the cause of an event merely because it happened before that event. This is another type of false cause fallacy. For example:
"Taekwondo is based on Karate since Karate was developed before taekwondo."
"The vitamin must work because two days after I started using it, my cold went away."
Joint Effect
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. For example:
"You have a fever and that is causing you to break out in spots." (In fact, both symptoms are caused by the measles.)
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 defeat the incumbent because you voted for her opponent because your vote had as much weight as any other vote, and hence is equally a part of the cause. For example:
"Smoking is causing air pollution."
"By leaving your oven on overnight, you are contributing to global warming."
Wrong Direction
The relation between cause and effect is reversed. For example:
"Leaves wiggling on trees makes the wind blow."
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. For example:
"The Challenger explosion was caused by the cold weather. (True, however, it would not have occurred had the O-rings been properly constructed.)
"People are in fear because of increased crime. (True, but this has led people to break the law as a consequence of their fear, which increases crime even more.)
