Monday, July 02, 2018

Black swans

When I made a bike ride last Sunday, by chance I passed a garden with two black swans behind a low fence. I felt pity for the swans, for I think that their wings had been clipped in order to prevent that they would escape, but maybe I am wrong. However, here I don’t want to talk about the harm we distress to each other and to animals. For every time I see a black swan I have to think of the great late philosopher Karl R. Popper. He used the example of black swans for showing why you cannot get true scientific theories via inductive reasoning – so by generalizing from data that support your thesis – and for substantiating his falsification principle. This principle says that you must look for data that refute theories and not for data that confirm them. Confirming data can always be found and will not make a theory better. It’s just refutations that lead to scientific progress. So if a theory says that all swans are white and you have seen already ten white swans, then the eleventh white swan you observe will not make your theory better, but a black swan will do.
Actually the black swans example wasn’t Popper’s. Already the Roman poet Juvenal used it, when he characterized something as “a rare bird in the lands and very much like a black swan”. By this he did not mean that the thing was a “white raven”, so a rarity, but that it was an impossibility, for the Romans assumed that there were only white swans. Till far in the 17th the expression “a black swan” remained equivalent to an impossibility. However, in 1697 the Dutchman Willem de Vlamingh and his co-explorers were the first Europeans to see black swans in Australia. The theory that all swans are white had been refuted.
All this is basic knowledge for epistemologists. What I didn’t know, but what I discovered when I was searching the Internet about this theme, is that there is also a black swan theory, developed by Nassim Nicholas Taleb. The Wikipedia says that it “describes an event that comes as a surprise, has a major effect, and is often inappropriately rationalized after the fact with the benefit of hindsight.” I let this theory pass, for then I would only copy what I read in the Wikipedia and on other websites. For I had to think of a general phenomenon: What is seen as a discovery is often quite a provincial affair. I have no idea whether there were white swans in Australia in 1697, but let’s assume that they lived there and that the Australian aboriginals knew that there are white swans and that there are black swans. Even then there would be a theory – namely in Europe – that says that there are only white swans and those who adhere to this theory thought that it was true. Maybe it was even thought that is was the Truth. But what was the case is that it was not the Truth, but that it was the truth for them, for there were other people in the world who knew better, but the adherents of the white swan theory hadn’t yet seen them, and for those who knew that there are black swans in this world it was not a problem.
Do you see the point? We (including scientists) consider a statement as true, not because it is true, but because we have the best data that makes it true for us (or because we consider our data as the best). But it is quite well possible that there are other people in the world who have facts at their disposal that would falsify our theory (also for us), but “we” simply don’t know it. That’s why scientists and others (often including “we”) are looking for such facts (according to Popper’s falsification principle). But this shows that truth, including scientific truth, is often a local or provincial view that is adhered to only in an odd corner of humanity, although it’s often a corner with a high status for some (like science). Then a discovery is only what’s known elsewhere but just not in this odd corner.
Does this mean that there are no “real” discoveries? Of course, there are. Often phenomena and facts are discovered that were not known before. By nobody. Nevertheless, even if we take this in account, I would say that truth is a lack of knowledge that things are different (and even can be different, for some). And maybe this is so for Truth as well.

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