  In the 1930s, Ludwik Fleck (1896–1961), a Polish-Jewish microbiologist, developed the first system of the historical philosophy and sociology of science. Fleck claimed that cognition is a collective activity, since it is only possible on the basis of a certain body of knowledge acquired from other people. When people begin to exchange ideas, a thought collective arises, bonded by a specific mood, and as a result of a series of understandings and misunderstandings a peculiar thought style is developed. When a thought style becomes sufficiently sophisticated, the collective divides itself into an esoteric circle (professionals) and an exoteric circle (laymen). A thought style consists of the active elements, which shape ways in which members of the collective see and think about the world, and of the passive elements, the sum of which is perceived as an “objective reality”.  What we call “facts”, are social constructs: only what is true to culture is true to nature. Thought styles are often incommensurable: what is a fact to the members of a thought collective A sometimes does not exist to the members of a thought collective B, and a thought that is significant and true to the members of A may sometimes be false or meaningless for members of B.