How to think about… Scientific truth | Innovation Tech

All swans are white. Or are they? It’s difficult to establish absolute truths about the world, and science is the worst method – apart from all the others

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VIENNA, 1919: a city scarred by lost war and empire. Navel-gazing is in order, and Sigmund Freud’s new ideas of the subconscious and psychoanalysis are all the rage. One young apprentice cabinet-maker is brooding – how could anyone prove them true, when the subconscious is unknowable?

Karl Popper soon abandoned cabinet-making for a loftier pursuit. He wanted to find a way to demarcate ideas like Freud’s from what he saw as a truer kind of knowledge: science.

It still isn’t at all easy. By its nature, science can’t rely on logical deduction alone, or build up knowledge purely from incontestable truths (see “How to think about… Logic”). It must make leaps into the unknown, just as Freud did, formulating hypotheses and searching for evidence of their truth.

This is called induction, and it hides a niggle described by philosopher David Hume 150 years before Popper. The classic example involves checking the colour of as many swans as you can find, then extrapolating a rule to say “all swans are white”. That sounds like science. But it can’t lead to reliable knowledge, Hume argued, because you can never know a black swan isn’t in the next pond.

Popper’s resolution seems oddly negative: science is about proving not truth, but falsehood. The crucial thing is that when you find evidence that disproves a scientific hypothesis, you discard or amend that hypothesis. You can never find truth exactly, but by slowly ruling out ideas, …

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