progressive and that there can be no demarcation in terms of method between science and any other form of investigation. Thought collectives In 1935, Ludwik Fleck, a Polish medical microbiologist publishedGenesis and Development of a Scientific Fact. Fleck's book focused on the epistemological and linguistic factors that affect scientific discovery, innovation and progress or development. It used a case study in the field of medicine (of the development of the disease concept of Syphilis) to present a thesis about the social nature of knowledge, and in particular science and scientific "thought styles" (Denkstil), which are the epistemological, conceptual and linguistic styles of scientific (but also non-scientific) 'thought collectives' (Denkkollektiv). Fleck's book suggests that epistemologically, there is nothing stable or realistically true or false about any scientific fact. A fact has a "genesis" which is grounded in certain theoretic grounds and many times other obscure and fuzzy notions, and it "develops" as it is subject to dispute and additional research by other scientists. Fleck's monograph was published at almost the same time as Karl Popper's Logik der Forschung but unlike Popper's work, the book received no review notice in Isis. However, Thomas S. Kuhn acknowledged the influence it had upon the Structure of Scientific Revolutions. Kuhn also wrote the foreword to Fleck's English translation. Falsifiability Popper coined the term "critical rationalism" to describe his philosophy. He distinguished between verification and falsifiability and said that a theory should be considered scientific if, and only if, it is falsifiable. Popper sought to explain the apparent progress of scientific knowledge in All Life is Problem Solving. Popper suggested that our understanding of the universe seems to improve over time because of an evolutionary process. He proposed that the process of "error elimination" in the field of science is like that of natural selection for biological evolution, whereby theories that better survive the process of refutation are not necessarily more "true" but more "fit" or applicable to the problem situation at hand. Popper suggested that the evolution of theories through the scientific method could reflect a certain type of progress: toward more and more interesting problems. Popper helped to establish the philosophy of science as an autonomous discipline within philosophy, through his own prolific and influential works, and also through his influence on his own contemporaries and students. Revolutions The mid 20th century saw a series of studies investigating the role of science in a