Karl Popper is one of the most significant philosophers of the 20th Century, whose ideas about science and politics robustly challenged the accepted ideas of the day. He strongly resisted the prevailing empiricist consensus that scientists’ theories could be proved true.

Popper wrote: “The more we learn about the world and the deeper our learning, the more conscious, specific and articulate will be our knowledge of what we do not know, our knowledge of our ignorance”. He believed that even when a scientific principle had been successfully and repeatedly tested, it was not necessarily true. Instead it had simply not proved false, yet! This became known as the theory of falsification.

He called for a clear demarcation between good science, in which theories are constantly challenged, and what he called “pseudo sciences” which couldn’t be tested.