The Semmelweis reflex or “Semmelweis effect” is a metaphor for the reflex-like tendency to reject new evidence or new knowledge because it contradicts established norms, beliefs or paradigms.
The term originated from the story of Ignaz Semmelweis, who discovered that childbed fever mortality rates reduced ten-fold when doctors washed their hands with a chlorine solution between patients. His hand-washing suggestions were rejected by his contemporaries, often for non-medical reasons. For instance, some doctors refused to believe that a gentleman’s hands could transmit disease (see Contemporary reaction to Ignaz Semmelweis).
While there is some uncertainty regarding the origin and generally accepted use of the expression, the use of the expression Semmelweis Reflex has been documented and at least used by the author Robert Anton Wilson. In his book The Game of Life,Timothy Leary provided the following polemical definition of the Semmelweis reflex: “Mob behavior found among primates and larval hominids on undeveloped planets, in which a discovery of important scientific fact is punished”. The expression has found way into philosophy and religious studies as “unmitigated Humean skepticism concerning causality”.