Popper's Theory: All Swans Are White

One of his strong beliefs was that the testability of a theory played a great deal in how respectable and interesting a theory was. He indeed saw theories as trials, as propositions made such as “all swans are white”. There are many ways to approach the colors of swans and several theories can be made on the topic: “some swans are white”, “there are more white swans than swans of other colors”, “all swans are green” and such. One could say that claiming that all swans are green is rather stupid and therefore would be a dumb theory to advance. This was not how Popper thought. He thought that a theory found its value in how testable it was and therefore, the claim that “all swans are green” would be a much better theory to him than the one stating that some swans are white. It is indeed easy to test the first one is as one non-green swan would suffice to falsify the whole theory. By doing so, Popper would let observation take care of the testing part of the process and not to the building of the theories up front. He would also rank theories that had not been falsified yet by how severely they had been tested. He did not have the answer to how good a theory was but believed that one could judge a theory compared to another. He even advanced that there might not even be a good theory but just an infinite number of theories, each better than the preceding and that the scientist’s job was to keep finding

His most famous critic was probably Thomas Kuhn, who is himself considered by many as the most influential philosopher of science of the 20th century. Kuhn was firmly against Popper’s idea that if a theory if proven wrong, the whole theory is to be thrown away. He claimed that it was slowing down the growth of science as everything would at some point end up being falsified and that it would become extremely difficult to advance new theories. Many scientists took part in the battle opposing Kuhn’s and Popper’s ideas. Imre Lakatos for instance was the one who tried to benefit from the conflict between their ideas in order to define a new philosophy combining both sides. His philosophy indeed tried to combine Popper’s view on how theories should be abandoned if proven false and Kuhn’s views on how a theory could be modified by ad hoc hypotheses in order to correct the main hypothesis. Other scientists such as Duhem and Quine also tried to take part in the debate by advancing a thesis known as the Duhem-Quine thesis stating that Popper falsification was practically wrong as he bases himself on observations and empirical evidence in order to falsify theories. They claimed that any empirical test could lead to a cascade of errors making it irrelevant to any serious scientific claim. For instance, a test refuting a theory based on an observation made by