On May 29th, 1919, exactly 100 years ago, an historic experiment took place. Einstein had published his General Theory of Relativity in 1915, and an opportunity arose during the solar eclipse of May 29th in 1919 to test his hypothesis. If light were indeed bent by gravity, then a couple of stars in the constellation of Taurus would be visible during the eclipse, not in the position that Newtonian physics suggested, but displaced by gravity. Two expeditions set out to test this, one by Dyson and Eddington to Principe island, the other by Crommelin and Davidson to Brazil. Both found the stars were indeed observed where Einstein’s theory predicted.

The young Karl Popper, aged 17 at the time, was powerfully influenced by this. His Vienna was abuzz with the radical ideas of Marx, Adler and Einstein. Adler had introduced the notion of inferiority complexes in childhood. Popper came across a case that didn’t seem to fit, and took it to Adler. He reported that Adler had no difficulty in explaining it in terms of his theory, even though he knew nothing about the person in question.

“How can you be so sure?” he asked Adler. The great man replied, “I know it from my thousand-fold experience.” To which young Popper replied, “And now I suppose it’s a thousand and one,” suddenly realizing that if all cases could be fitted into the theory, none could ever test it. It was the same with Marx’s theories - they could explain everything that happened, no matter what outcome prevailed. Einstein was different. His theory lived dangerously. If the two stars had not appeared in their predicted positions, his theory would have had to be discarded. Popper realized then that theories had to be capable of being tested, and rejected if observations went against them.

It was an insight that led to his “Logic of Scientific Discovery,” rejecting induction in favour of what he called “conjecture and refutation,” meaning that creative proposals had to be tested against the world of our observation. It lies at the core of neoliberalism. Marxism and socialism interpret the world, but neoliberalism seeks to change it by applying techniques that work in practice. Its record has far surpassed that of its rivals. It has created the wealth that has lifted men and women out of degrading subsistence toil and given them opportunities for advancement undreamed of by previous generations. It has lowered death rates, increased lifespan, conquered diseases, and generally improved the condition of humankind.

The importance is testing. If observed reality goes against a practice, it has to be modified or rejected. Socialism, by contrast, rejects the evidence if observation shows that it fails to achieve its objectives. If it does not bring the promised equality and prosperity, its advocates claim that “it wasn’t really socialism.” Thus socialism can never be disproved, and cannot, therefore, contain any insights of value about the real world, the one that we live in.

On that day 100 years ago, we learned something important, that theories have to be tested against the observed world. Depending on how they perform, they have to be modified or rejected, and only the useful ones are retained. This is why neoliberalism has improved the world, and why socialism has not.