Changes

 In the early 20th century, logical positivists like Rudolf Carnap attempted to work around the purported fallibility of science. They would argue that phenomena must be verifiable to be considered scientific – that in principle a theory must have the potential to be tested and confirmed3confirmed [[CiteRef::Carnap (1936a)|p. 420]]. A theory that suggested that imperceptible fairies were responsible for the pushing the earth around the sun would be non-science as it could never be proven true or false.  Later, Karl Popper would argue for a standard of falsifiability: a theory should be, again in principle, the possibility of being found untrue4. While a theory may posit a testable hypothesis, it is only scientific if the outcome “false” is possible. Marxist theories Theories were sometimes guilty of post-hoc explanations for any number of phenomena, resulting in them never being proven false, and therefore being non-scientific according to Popper[[CiteRef::Popper (1959)|p. 17]]. In a similar vein, Imre Lakatos argued that theories should be assessed as progressive and degenerative “research programs,” with the latter classified as unscientific5unscientific [[CiteRef::Lakatos (1970)]]. Research programs that increased in predictive power were progressive, while those whose theories gradually weaken in available evidence and predictive power were considered degenerative. For his part, Thomas Kuhn argued that within periods of “normal science” (where basic concepts and practices are free from radical change), puzzle or problem solving is what qualifies as science Kuhn¬¬[[CiteRef::Kuhn (1970b)]].  However, this wide array of prospective theories has failed to materialize a consensus. Partially, this is a consequence of the apparent inconsistency in the historical record of science. As Paul Feyerabend would say, there is no rule in the sciences that appears to be inviolable, including the purported demarcation between science and non-science6science[[CiteRef::Feyerabend(1975a)|p. 9-10]]. As such, among philosophers of science the question of demarcation remains open, much to the chagrin of philosophers such as Larry Laudan. Laudan saw this failure, along with the social factors that inflamed debate surrounding the status of pseudoscience, as proof that the problem of demarcation was useless[[CiteRef::Laudan (1983a)|p. 112]].