Falsification

Amazon gives a summary of Popper’s essays in ‘Conjectures and Refutations’:

“The way in which knowledge progresses, and especially our scientific knowledge, is by unjustified (and unjustifiable) anticipations, by guesses, by tentative solutions to our problems, by conjectures. These conjectures are controlled by criticism: that is, by attempted refutations, which include severely critical tests. They may survive these tests; but they can never be positively justified: they can neither be established as certainly true nor even as ‘probable’ (in the sense of the probability calculus). Criticism of our conjectures is of decisive importance: by bringing out our mistakes it makes us understand the difficulties of the problems which we try to solve. This is how we become better acquainted with our problem, and able to propose more mature solutions: the very refutation of a theory – that is, of a tentative solution to our problem – is always a step forward that takes us nearer the truth. And this is how we can learn from our mistakes. As we learn from our mistakes our knowledge grows, even though we may never know – that is, know for certain. Since our knowledge can grow, there can be no reason here for despair of reason. And since we can never know for certain, the can be no authority here for any claim to authority, for conceit over our knowledge, or for smugness.”

Like Hume then Popper seems to ultimately have a sceptical view of knowledge: It is not possible to achieve certainty, merely probability. The ‘anticipations’, ‘guesses’, and ‘hypotheses’ of science are always unjustified and unjustifiable. Hume explains that this justification is lacking due to our unsupported supposition that the future will conform to the past. Popper accepts that I have no rational justification for any theorising of science.

How then does science proceed? How can science be said to bring us closer to ‘knowledge’ if it provides only probability and never certainty?

Popper sees science as a series of ‘conjectures’ (the guesses we make make about what may be true) and ‘refutations’ (which test the reliability of our conjectures). For this view of science to operate effectively the conjectures we make must be refutable. We must accept that it is possible to show that the conjecture is false. Popper labels this quality ‘falsifiability’.

Since Popper’s writing ‘falsifiability’ has become (while not universally accepted) a foundation for the modern scientific method. Consider the diagram below:

When we create an hypothesis we can deduce from it some predictions of the future. We can then conduct an experiment, or observe the natural world to test our predictions. From these observations (empirical reasoning) we can induce the necessary alterations to our hypothesis, or in the event that it’s confirmed we can accept it as more highly probable. We can then make further predictions from our new hypotheses and the process continues refining itself.

“All swans are white” is a falsifiable theory. I can falsify it with the observation “this swan is black” The statement “white swans exist” is not falsifiable however (nor for that matter is the statement “pink swans exist”). In both cases we cannot prove the statement with certainty using a positive method. No matter how many swans I observe I cannot logically induce a general rule from individual observations with certainty. I can prove with certainty that the falsifiable statement is false though, and in doing so I progress science by forcing a new hypothesis to be created.

Bertrand Russell put forward a theory (deliberately absurd and unfalsifiable) that a teapot was orbiting the sun on a path between Earth and Mars. Such a theory fails Popper’s test of falsifiability, because there is no experiment I could conduct, and no observation I could make (the teapot is too small to be seen by telescope), which disproves his theory. Russell’s point was that to assert this theory, and to insist – on the grounds that it has not been refuted – that the theory be accepted as truth is nonsensical.

Using Popper’s falsification test we can assess whether a claim, or theory, is genuinely scientific. A scientific claim will be (or should be) falsifiable. A claim which is clearly not scientific (“Beyonce is better than Nicki Minaj” for instance) need not be falsifiable, provided I don’t try to suggest that it is science. Where a claim seems scientific, or is presented as science, but is not falsifiable, we can classify that claim as pseudo-science. Popper felt that this was a black and white distinction. He felt that falsification could differentiate between science amnd pseudo-science, but more recently people have begun to accept that there may be some grey area between.  Some pseudo-sciences are a dark grey, others are light grey.

But what of Russell’s teapot? The theory may be obviously unfalsifiable today, but in the future some technological or exploratory process may be put in place which allows us to conclusively prove that such a teapot does not exist. Does this show that Popper’s black-and-white view of falsification, of science and pseudo-science is flawed?

It’s important to remember that just because something is not falsifiable doesn’t necessarily mean it is not true. “My child is beautiful” may well be true, but I cannot falsify it (much like my Beyonce v Minaj example earlier). Likewise, a statement like “Angels exist” is not falsifiable, but that doesn’t mean we can automatically reject it as false. Even Russell’s Teapot was not supposed to deny the existence of God (Russell did that too though), it was meant to demonstrate that the theists had the burden of proof.