Introduction: Genesis and Development of a Scientific Fact revisited

‘If one wants to study scientific facts’, explained the bacteriologist and philosopher of science Ludwik Fleck in 1935 in the introduction of his book Genesis and Development of a Scientific Fact – today viewed as a pioneering study in the sociology of scientific knowledge – ‘a medical fact, the importance and applicability of which cannot be denied, is particularly suitable, because it also appears to be very rewarding historically and phenomenologically. I have therefore selected one of the best established medical facts: the fact that the so-called Wassermann reaction is related to syphilis.’

Fleck's choice of the Wassermann reaction was motivated by two reasons. One was the central role of this test in the development and the present structure of his own scientific specialty – serology. The other was the observation that the most famous serological reaction was based on the use of a non-specific antigen and was thus squarely in contradiction with fundamental principles of immunology and serology. These principles had been summed up in 1910 by Wassermann's collaborator Julius Citron. The fundamental law of immunology, Citron explained, is that ‘every true antibody is specific and that all nonspecific substances are not antibodies. The law of specificity is the precondition of immunodiagnostic.’ This particularity of the Wassermann reaction was central to Fleck's argument that additional, sociologically based explanations are needed to account for the genesis and rapid diffusion of this test.