False Analogy

Description:

The argument draws a conclusion from observed cases that are only superficially or apparently similar to the unobserved cases about which the conclusion is being drawn.

Comments:

The fallacy applies only to inductive arguments that draw a conclusion, not to a whole class, but to other members of the class, or what are called "unobserved cases."

Examples:

"Just as in time the gentle rain can wear down the tallest mountain, so, in human life, all problems can be solved by patience and quiet persistence."

We shouldn't put so much effort into adult literacy programs. After all, there's no point crying over spilled milk."

Discussion:

Some analogies are not false. Indeed, it could be argued that analogical reasoning is at the very foundation of all formal, rational thought. It is reasoning by analogy that allows us to generalize from specific instances to general forms or abstract principles. For example, the form

All M are P.
S is M.
S is P.

is merely a statement of what the argument "All men are mortal, and Socrates is a man, so Socrates is mortal," has in common with all other arguments that also subsume a case under a general rule. If we were unable to reason by analogy, we would be unable to tease this general form out of the many arguments that follow this pattern. Formal reasoning is based on our ability to recognize relevant similarities.

Of course, the fallacy of False Analogy mimics good reasoning by relying on our ability to recognize similarities, and upon our (highly valuable) tendency to draw conclusions based on those similarities. However, the fallacy of False Analogy errs by confusing irrelevant similarities with relevant similarities. The error of False Analogy is exposed by pointing out important and highly relevant dissimilarities between the cases cited in the premisses and the cases about which the conclusion is being drawn.

Source: Abraham Fraunce, Lawiers Logike, 1588. It was first treated as an Inductive fallacy by John Stuart Mill in A System of Logic, 1843.

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