Causal Reasoning

　　Of the three types of inductive reasoning we will discuss， causal reasoning

　　is both the weakest and the most prone to fallacy. Nevertheless， it is a us

　　eful and common method of thought.

　　To argue by causation is to claim that one thing causes another. A causal ar

　　gument can be either weak or strong depending on the context. For example， t

　　o claim that you won the lottery because you saw a shooting star the night b

　　efore is clearly fallacious. However， most people believe that smoking cause

　　s cancer because cancer often strikes those with a history of cigarette use.

　　Although the connection between smoking and cancer is virtually certain， as

　　with all inductive arguments it can never be 100 percent certain. Cigarette

　　companies have claimed that there may be a genetic predisposition in some p

　　eople to both develop cancer and crave nicotine. Although this claim is high

　　ly improbable， it is conceivable.

　　There are two common fallacies associated with causal reasoning：

　　1. Confusing Correlation with Causation.

　　To claim that A caused B merely because A occurred immediately before B is c

　　learly questionable. It may be only coincidental that they occurred together

　　， or something else may have caused them to occur together. For example， the

　　fact that insomnia and lack of appetite often occur together does not mean

　　that one necessarily causes the other. They may both be symptoms of an under

　　lying condition.

　　2. Confusing Necessary Conditions with Sufficient Conditions.

　　A is necessary for B means “B cannot occur without A.” A is sufficient for B

　　means “A causes B to occur， but B can still occur without A.” For example，

　　a small tax base is sufficient to cause a budget deficit， but excessive spen

　　ding can cause a deficit even with a large tax base. A common fallacy is to

　　assume that a necessary condition is sufficient to cause a situation. For ex

　　ample， to win a modern war it is necessary to have modern， high-tech equipme

　　nt， but it is not sufficient， as Iraq discovered in the Persian Gulf War.

　　SEVEN COMMON FALLACIES