  In this process there is nothing necessary; various accidental circumstances decide which ideas become a basis for investigation and are disseminated within a collective; which meetings between scientists happen; which research projects acquire social support; which experiments are conducted first etc. Fleck claims that if e.g. Sigle’s idea of protozoa-like structures as the causative agent of syphilis had acquired sufficient support, we would have reached a harmonious system of knowledge different from the current one. The scope of the name “syphilis” would have been somewhat different than it is today, just like the methods of research and therapy would. But when a certain thought style develops and dominates researchers’ minds, alternative ways of development become closed. Summing up this idea Fleck claims that most—and maybe even the whole—content of scientific knowledge is conditioned by historical, psychological and sociological factors and one has to consider them when attempting to explain that content (1935a, II.1).