Historical fallacy

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Not to be confused with Historian's fallacy.

The Historical fallacy, also called the psychological fallacy, is a logical fallacy originally described by philosopher John 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." ^[1] More simply stated, one commits the historical fallacy when he reads into a process that which comes about only as a result of that process.

An example is helpful for understanding the concept:

To give an example of this that is easier to understand, imagine you have come to Earth from another planet and are examining a loaf of bread to discover how it was made. Thinking exclusively in terms of parts and ingredients you might proceed to analyze (break into parts) the various ingredients in the bread. You would, for instance find wheat, but also air. You might conclude then that part of the process of making bread includes mixing in some air. This is wrong. A baker does not mix air into his bread. Rather he adds yeast and a chemical process (when heated for a duration) causes air to rise in the bread. By not understanding the "historical fallacy" you have read into the process, as one of its components, something that comes about only as a result of that process. You imagined air as part of the cause, when in fact air is merely a result of the process. You read the effect into the cause. That is the historical fallacy. In process theory effects are considered to supervene upon processes that are not necessarily reducible to the parts of that process.

The historical fallacy has implication in psychology, analytic philosophy, logic, and metalogic. For instance many postmodern analytic philosophers apply logic to understanding metaphysics before first inquiring into the cognitive and perceptual processes which give rise to logic itself. Thus many process theorists might contend that much of analytic philosophy is undermined by the historical fallacy.