Changes

|Prehistory=In the early twentieth century, many [[Rudolf Carnap|logical empiricists positivists]] supported a confirmationist view of theory assessment, in which theories are assessed on the basis of the balance of confirming and disconfirming evidence. In 1945, [[Carl Hempel]], a logical empiricist and confirmationist, argued that an agent might take three stances towards a theory, ''accepting '' it, ''rejecting '' it, or ''withholding judgment'', based on confirming or disconfirming evidence. [[CiteRef::Losee (2001)|p. 167-168]][[CiteRef::Hempel (1945)]] In his ''Logic of Scientific Discovery'' (1959), [[CiteRef::Popper (1959)]] [[Karl Popper]] argued for a falsificationist view of science. Scientific ideas gained ''acceptance'' when they had survived strong tests in which their unexpected novel predictions were verified, and where ''rejected'' when they failed to survive such tests. [[CiteRef::Thornton (2015)]][[CiteRef::Godfrey-Smith (2003)|p. 57-74]] [[Thomas Kuhn]]'s ''Structure of Scientific Revolutions'' (1963) used a number of equally vague terms to refer to stances a community might take towards a theory, including ''universally received'', ''embraced'', ''acknowledged'', and ''committed to''.  In [[Imre Lakatos]]'s theory of scientific change [[CiteRef::Lakatos (1970)]] Individual theories were encompassed in larger assemblages called research programs. A research program consists of a family of scientific theories either sharing a hard core of empirical content, or a close association with having such content. Lakatos identified two epistemic stances with respect to research programs. A research program was ''progressive''