I remember Karl Popper (1902- 1994) from my time doing a PhD at The London School of Economics and Political Science (the famous LSE). He used to give lectures on political philosophy which attracted great crowds of students. He was a rather wizened, bald-headed character with a thick Austrian accent, very forceful.

One thing I took away from his classes was his strong assertion that a scientific fact, or theory, could not be proved. Hypotheses could be advanced, but could not be proved. They could only be disproven. Science, he said, was a constant process of thinking up hypotheses from the available data, then systematically testing them. If they held up, so far so good. That could be taken as the given “truth” as long as it was not disproven.

This “falsification” principle would become a leading paradigm until it itself was challenged by new philosophers (such as Thomas Kuhn). Popper welcomed such debate. This was what science should be about.