Karl Popper (1902 –1994) was an Austrian-British philosopher and best known for his inquiries into how we create scientific knowledge and how it differs from other kinds of knowledge. The key problem he faces up to is that we cannot rely on induction (no matter how many white swans we have seen we cannot say that all swans are white) so instead we have to have a deductive method of testing theory, i.e. science should proceed by putting forward theories, testing them and see how they apply.

This might make him sound positivist. However Popper was fully aware that knowledge was subject to change or fallible. In this sense something better might come along. But why would we need something better to come along in the first place? Like Kuhn some years later, Popper thought that scientific knowledge emerged from facing up to new problems and our attempts to solve them. This meant theorising. Theorising was a creative process. New theories could not be created by following empirical observation (for all observation was theory laden) but required a leap of the imagination, we might call this guess work. However new proposals for theories needed to be tested. The process involved: first an analysis of the internal consistency of the theory; second, a break down between empirical and logical elements; third, step a comparison with existing theories to say whether it offers an advance (eg by dealing with a problematic issue. Only then does the theory need to be tested empirically, but note this is testing for corroboration not verification.

Theorising may mean proposing radically different ways of seeing phenomena but he was less radical than Kuhn. New theories could build on old ones or at least take account of them and should be compatible with all known observations. This gave a sense of continuity. Popper's account of scientific knowledge cannot lead us to think of the outcome of science as establishing truth but it does carry a sense of scientific progress.

His willingness to contemplate the fallible nature of knowledge led Popper into making the case for a free society, one in which actions are monitored and critiqued.

Popper can be seen as interesting point in the development of philosophy of science at a time when undermine logical positivism in philosophy and in social theory but still a long way from later more radical criticism of modernism. One area of tension remains in how categorical Popper wants to be in respect to ruling out induction. The white swans example is telling as indeed black swans were later found in Australia, not all swans it transpired were white. But surely on the balance of probability we can accept that by induction some things are likely to the case. At times Popper does concede this.

To read more:

Magee, B. (1974). Popper. London: Fontana.

Popper, K. (1959). The Logic of Scientific Inquiry. London: Routledge.

For an in-depth overview go to:

Thornton, Stephen, "Karl Popper", The Stanford Encyclopedia of Philosophy (Summer 2017 Edition), Edward N. Zalta (ed.), URL = <https://plato.stanford.edu/archives/sum2017/entries/popper/>.