Alison Goddard reports on revelations and revels at the annual meeting of British philosophers in Belfast
Sir Karl Popper, the philosopher who devised a test to distinguish between science and pseudoscience, hid early work that shows he held contradictory views, an Italian academic has found.
Popper, who was professor of logic and scientific method at the London School of Economics for 23 years and who died in 1994, is best known for devising falsificationism.
He argued that a scientific idea can never be proven true because, no matter how many observations seem to agree with it, it may still be wrong. On the other hand, a single contrary experiment can prove a theory to be false. For example, the idea that all swans are white cannot be proven by observing many white swans. It can only be proven false by sighting a black swan.
Now Stefano Gattei of the Universita degli Studi, in Milan, has found evidence that Popper originally believed that it was possible to reason through induction from observation to theory. He told philosophers gathering for the annual meeting of the British Society for the Philosophy of Science in Belfast last week: "As the author of The Logic of Scientific Discovery and of many later works, (Popper) clearly states not only that science does not proceed by inductive inferences but, also, there simply is no such logical entity as an inductive inference.
"However, the young Popper thought quite differently. Indeed, if we read his early unpublished writings, we see that he clearly held an inductivist position. In his later reconstructions of the development of his own thought, Popper seemed determined to remove any trace of this early inductivism."
Popper claimed that he first devised the work that culminated in falsificationism in 1919. However, a paper from 19 discovered by Mr Gattei shows that Popper still accepted induction almost a decade after he claims to have abandoned it. Mr Gattei believes that this is evidence that it took ten years for Popper's ideas to crystallise, first into a criticism of induction and then into the demarcation between science and pseudoscience.
While much of Popper's early work had been donated to public collections, the crucial paper, "Gewonheit" und "Gesetzerlebnis" in der Erziehung , was in Popper's personal collection on his death.
Mr Gattei said: "It's just a personal conjecture, but maybe he didn't want others to know he was an inductivist in earlier years. There's just one copy of the thesis, and that was in his personal papers until he died.
"Popper used to keep everything. Even if he didn't like (his earlier ideas) at all or want others to know, he would have wanted to keep the work as reference."