Every week the accumulation of research papers in this and other journals across the world adds to our knowledge and understanding of biology, disease, and treatments. The past 100 years have seen huge advances in medicine’s ability to relieve suffering and to extend life. The paradox is that we seem to forget as much as we learn as fast as we learn. Someone whose contribution we seem in danger of forgetting, at least in medicine, is Karl Popper, professor of logic and scientific method at the University of London from 1949 to 1969.

Popper argued: “It might be well for all of us to remember that, while differing widely in the various little bits we know, in our infinite ignorance we are all equal.” And he warned us to “suspect all those who claim that they are authorized to teach the truth.” His crucial assertion was that we can never establish the truth of any scientific theory; we can simply subject it to the severest tests in a deliberate attempt to prove it false. The most we can then claim is that any given …