Also called the weak or faulty analogy fallacy, the false analogy fallacy occurs when a writer or speaker uses an analogy which poorly compares two things in order to illustrate a concept or idea. Strong analogies are frequently used with success to illustrate difficult concepts or a specific side of a controversial issues. False analogies, however, are often used either intentionally or unintentionally to support ideas which are either poorly argued or lack evidence.
In analogies, one concept is compared to another similar concept in order to make a point or clarify one of the concepts. All analogies make this basic claim: concept A and concept B are similar. Therefore, since X is true for A, it must also be true for B.
Most analogies are not stated with this structure, however. For example, in the 1998 movie, Playing By Heart, the character Joan states, "talking about love is like dancing about architecture." Though love and architecture are generally dissimilar, she is making the claim that talking about love and dancing about architecture are similar, and that since dancing about architecture seems a ridiculous concept, trying to talk about an emotion as complex as love is equally ridiculous. In other words, talking about love and dancing about architecture are similar. Therefore, since it is ridiculous to dance about architecture, it is ridiculous to talk about love.
Fallacies are errors in logical reasoning which occur in arguments. The false analogy fallacy occurs when the analogy used is inappropriate for the circumstances and assumes incorrectly that because something is true about one example in the analogy, it is true about the other. Since in strong analogies this reasoning is sound, the false analogy fallacy is considered a fallacy of an informal argument. Informal arguments deal with the content of the argument, whereas formal arguments deal with the structure of the argument.
A false analogy fallacy may be very obvious or may seem at first to be a strong analogy. For example, in an article about unruly children, the author might use the analogy that children are like monkeys to illustrate a point. Anyone who has seen a group of children playing on a jungle gym can likely appreciate the resemblance between a child and a monkey, so this analogy may, at first, appear to be strong. If the author goes on to say, however, that since monkeys cannot be reasoned with neither can children, the analogy becomes weak. Although there may be many superficial resemblances between children and monkeys, children still possess language and reasoning skills monkeys do not.