Popper and the Theory of Evolution A Critical Evaluation.
Sir Karl Popper, one of the philosophers who believe there is one single fixed method by which scientific theories are discovered, is recognized as a distinguished figure in philosophy of science mainly due to his Falsification Principle. He contends that scientific theories are not verifiable but only falsifiable, and proposed the method of conjectures and refutations. .
There were a few theories that interested Popper in 1919, namely Einstein's Theory of Relativity, Marx's theory of history, Freud's theory of psycho-analysis and Alfred Adler's so-called "Individual psychology". Popper argued that the latter three theories were able to explain in hindsight phenomena that fell within their domain. These hind-sight explanations were always possible by invoking additional assumptions, exploiting conceptual vagueness, or making conceptual modifications solely designed to make the evidence appear to follow from their fundamental principles and to prevent refutation of their position by new empirical data (Bala, Arun. "Popper's Strategies for Critical and Creative Thinking", 2001). .
On the contrary, Popper found Einstein's theory, which predicted that light will be bent by heavy bodies like the sun particularly impressive because it involves risk. Einstein's prediction contradicted the then dominating Newtonian theory of gravity. However, in 1919, Eddington's eclipse observation led to the first confirmation of Einstein's theory, and hence Newton's theory was considered falsified because this observation refuted it. Yet, if observations deny Einstein's prediction, Einstein's theory would have been discarded, so Einstein's theory was falsifiable although it was not falsified. Hence, Popper thinks that logically no amount of inductive evidence can prove a universal statement but a single piece of counter-evidence can falsify it. He argued that since it is always easy to find confirmations and hind-sight explanations that will serve to save a theory, therefore a scientific theory should not be identified as one that is well verified, but one that involves risks and can stand severe tests targeting to refute the theory.