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|Prehistory====Ludwig Ludwik Fleck===[[Ludwig Ludwik Fleck]], an epidemiologist, made one of the earliest attempts to understand scientific change as a social process, and to develop a conceptual framework for understanding how scientific communities function.[[CiteRef::Sady (2016)]] His most comprehensive work was ''Genesis and Development of a Scientific Fact'' published in 1935.[[CiteRef::Fleck (1979)]] For Fleck, cognition was necessarily a collective social activity, since it depends on prior knowledge obtained from other people. New ideas arise within ''thought collectives'', which are groups of people who participate in the mutual exchange of ideas. As an emergent consequence of mutual understandings and misunderstandings within such a group a particular ''thought style'' arises. An established thought style carves the social world into an ''esoteric circle'' of expert members of the thought collective, and an ''exoteric circle'' who are outside the thought collective. How individual members of a thought collective think and perceive within the relevant domain is determined by the thought style. Scientific facts are socially constructed by thought collectives. Reality in itself cannot be known, but the thought style can be compared with reality through observation and experiment, and may be revised or abandoned on the basis of such interactions.[[CiteRef::Fleck (1979)]] [[CiteRef::Sady (2016)]] The thought style of a particular collective can, at most, be only partially understood by members of other collectives, and may be completely ''incommensurable'' with the thinking of some other collectives.