The matter of how pseudoscience is differentiated from science. This is difficult question to address because neither term has a precise and universally accepted definition. A trawl through some dozen books on the philosophy of science shows that only one had considered this question, which is a clear indication that this is not a matter with which philosophers concern themselves. The outstanding exception is Sir Karl Popper (1902-1994). By his own account, he enunciated the principle of falsifiability as a young man in response to his disillusion with the spurious claims of personality psychology and Marxist political economy. This principle says that a claim proposition or theory can only be considered scientific if a test can be devised that could, if failed, show it to be wrong. As Popper explained in The Logic of Scientific Discovery (1934) and in Conjectures and Refutations (1963): It is falsifiability, not verifiability “that is to be taken as a criterion of demarcation” between scientific and nonscientific (or pseudoscientific) theories. “A theory which is not refutable by any conceivable event is non-scientific; . . . every genuine test of a theory is an attempt to falsify it.” In Popper’s view, there were many areas being given attention and claiming to be scientific that defied contradiction; their supporters were convinced of their truth, and no test could be devised which would shake that belief. If opponents produced what they thought was evidence that discredited the theory, its supporters shifted ground, shouted foul, explained that the conditions were unfavorable, or in some way sidestepped the objection. They knew they were right. There was no test that they would accept which would shake their belief. To Popper, such theories were pseudoscience and their advocates pseudo¬ scientific. Yet, such people claimed that they were scientists because they were always verifying their theories in the way approved by the “positivists” of the Vienna circle. Also, Popper’s principle had another important significance: It was essential to the progress of science science develops through scientists’ conjectures and nature’s refutations. For the young Popper, real science was shown by Einstein’s invitation to the astronomers to refute his general theory of relativity with the results of the forthcoming eclipse of 1919.
This was an interesting and persuasive argument, and other philosophers gave it some consideration a whole new area to be explored. They soon showed it to have problems, principally that the history of science showed that in practice scientists didn’t work like that. Maybe the science community ought to reject immediately any theory that failed the agreed test, but the evidence showed that the community doesn’t (or, at any rate, hadn’t); many respectable and respected scientists had doggedly clung to their theories long after they had failed the early test or tests and had behaved in the way Popper had described as pseudoscientific. Only after some time and repeated and refined testing had their theories triumphed. For example, both classical physics (Copernicus and Newton) and relativity physics (Einstein) would have been summarily rejected if Popper’s falsifiability criterion had been ruthlessly applied. Furthermore, it is not always possible to get agreement on an acceptable falsification test. And adherents and skeptics disagree about whether a particular result is a falsification, and theories that the science community is adamant are pseudoscientific are sometimes open to falsification, for example Rupert sheldrakes hypothesis of formative causation.