The Historical fallacy, also called the psychological fallacy, is a logical fallacy originally described by philosopher John Dewey in The Psychological Review in 1896. According to Dewey the historical fallacy occurs when "A set of considerations which hold good only because a completed process is read into the content of the process which conditions this completed result." More simply stated, one commits the historical fallacy when one reads into a process the results that occur because of that process. John Dewey writes:
- "The fallacy that arises when this is done is virtually the psychological or historical fallacy. A set of considerations which hold good only because of a completed process, is read into the content of the process which conditions this completed result. A state of things characterizing an outcome is regarded as a true description of the events which led up to this outcome; when, as a matter of fact, if this outcome had already been in existence, there would have been no necessity for the process."
A person coming across a loaf of bread without knowing the process by which bread is made, might begin to try to understand how to make bread by analyzing only its ingredients. Finding that bread contains a large amount of gas, one might conclude that gas is an ingredient used in making bread. However, a baker does not add gas into bread. Rather, yeast creates a chemical process that causes the bread to rise with bubbles of carbon dioxide gas. The fallacy is in not recognizing that the gas is a result of the process of making bread and not a preexisting ingredient used to make it. Completed results supervene upon processes that are not necessarily reducible to the parts or stages of that process.
- The Reflex Arc Concept in Psychology, John Dewey, The Psychological Review, VOL. III. No. 4. July 1896. p. 367