Kekule's Dream

Genetic Fallacy

Type: Red Herring


Difficult as it may be, it is vitally important to separate argument sources and styles from argument content. In argument the medium is not the message.


Source: Bruce N. Waller, Critical Thinking: Consider the Verdict (Third Edition) (Prentice Hall: 1998), p. 5.


The Genetic Fallacy is the most general fallacy of irrelevancy involving the origins or history of an idea. It is fallacious to either endorse or condemn an idea based on its past—rather than on its present—merits or demerits, unless its past in some way affects its present value. For instance, the origin of evidence can be quite relevant to its evaluation, especially in historical investigations. The origin of testimony—whether first hand, hearsay, or rumor—carries weight in evaluating it.

In contrast, the value of many scientific ideas can be objectively evaluated by established techniques, so that the origin or history of the idea is irrelevant to its value. For example, the chemist Kekulé claimed to have discovered the ring structure of the benzene molecule during a dream of a snake biting its own tail. While this fact is psychologically interesting, it is neither evidence for nor against the hypothesis that benzene has a ring structure, which had to be tested for correctness.

So, the Genetic Fallacy is committed whenever an idea is evaluated based upon irrelevant history. To offer Kekulé's dream as evidence either for or against the benzene ring hypothesis would be to commit the Genetic Fallacy.