"Conjectures and Refutations" by Karl Popper

This is a classic work of philosophy in which Popper explains his Criterion of Falsifiability to separate Science from Non-Science. Why, he asks, is Einstein's work so different from that of, for example, Marx or Adler. The answer he gives is that Einstein makes precise predictions which can be tested whereas Marx and Adler offer vaguer forecasts. For example, the General Theory of Relativity proposed that light would be bent by a gravitational field and that therefore we would be able to see stars during a solar eclipse that were behind the sun, invisible unless light bent. If the stars could not be seen, Einstein would be wrong. In other words, Einstein's theory was easy to refute (and, to add spice, it would be refuted if light travelled in straight lines as everyone had hitherto believed). But Eddington photographed the eclipse and Einstein was acclaimed. On the other hand, Adler's theories are often so vague that they can predict either of two opposite occurrences. As for Marxism, it made some precise predictions which were falsified but the theories were then adapted so the theories fitted the facts. In Popper's view, such theory-elasticity in non-Scientific.

Popper believes that Science proceeds thus: a scientist makes a hypothesis, testable predictions are generated, these are then tested and, if they are found to be false, the hypothesis is discredited and a new one dreamed up. The more falsifiable the predictions, the sooner they can be refuted and the quicker Science can progress.

Many people have criticised Popper's views. He says nothing about how the hypotheses are generated in the first place. He does not give sufficient weight to how observations are made in the context of theories so that what is observed may be inaccurate or spurious. He fails to acknowledge sufficiently that most theories have refuting observations but these are usually treated as anomalies, the theory is still believed in spite of them, unless and un til the 'time has come' for the theory to be refuted. And he fails to account for the fact that Science might be unable to proceed if refutations were too easily able to displace a theory.

In my mind Science progresses like the sandpiles of Per Bak. The anomalies add to the theory like grains of sand add to the pile. Normally there are a few trickles down the pile as the theory adjusts itself. But sometimes, unpredictably, a grain of sand starts an avalanche and the theory is refuted and another one steps in to take its place. And the process starts all over again.

And Science would not be possible if the grains slipped too easily (perpetual avalanches would result in paradigm overload - perhaps this is the problem with the social sciences) or hardly ever slipped resulting in knowledge becoming fossilised a bit like scholasticism in the middle ages (though James Hannam might disagree with me).

Per Bak is the author of How Nature Works, a brilliant book about the phenomenon of self-organised criticality in the context of a wide range of complex systems including an ecosystem. Read it!

James Hannam is the author of God's Philosophers, an equally brilliant book about the growth of scientific knowledge in the middle ages.

April 2016; 415 pages