A Popper-Kuhn hybrid theory of scientific knowledge

I may be an amateur in philosophy of science, in addition to being a professional natural scientist. I have read several books of Popper, and several of Kuhn. I regret very much that Popper fans and Kuhn fans tend to denounce each other. In my opinion, thoughts of these thinkers are helpful when (may I say "and only when"?) combined.

Popper (1959) said that logic is in the basis of science. Scientific theories contain such universal statements (often called "laws" or "rules"). They typically take the form of "All A's are B's", and this can be refuted ("falsified") if there is something which is certainly an A but certainly not a B.

But where in the world the logical concepts reside? Is it in the real world ("World 1" of Popper 1972)? While whether logic is intrinsic in the real world is a very difficult philosophical question, it seems certain that the logical concepts which we actually operate are constructions by human minds. But they are not just parts of subjective minds ("World 2" of Popper) which persons individually have but do not share each other. They are part of what Popper called "objective knowledge", or "World 3", that is, pieces of knowledge shared by people, which can (sometimes) have lives longer than the persons who created them.

Science operates concepts in the World 3, but it is eventually an activity to gain a system of objective knowledge about the World 1. So there must be correspondence, or "mapping" (in mathematical sense), between the concepts in the World 3 and phenomena in the World 1. Is the mapping obvious and unique? I do not think so. (Maybe I depart Popper here, though I am not sure.)

Two persons, X and Y, who apparently study the same issue may have apparently the same statements like "All A's are B's" and "There is something that is an A but not a B". But they may differ in what phenomena in the World 1 correspond to A. For instance, X thinks that an object C is an A but not a B, but Y does not think that C is an A. Then, even though they share the same logical principles and apparently the same language, they may differ in the decision whether the universal statements is refuted or it is still enduring.

In Kuhn's (2000) terminology, X and Y have different lexicons. I understand that "a lexicon" means a system of concepts which are used in making scientific statements. Validity of operations of logic, typically "falsification" (to prove a hypothesis to be false), is only shared among a group of people who share a lexicon, at least approximately. If they do not share the lexicon, but if they are not aware of that, their conversation may be absurd. Following Kuhn (2000), I think that this is a case of Kuhn's controvertial concept "incommensurability".

The group of people who share one lexicon are usually recognized as a disciplinary community. How the members share the lexicon? Very few times by teaching the definition of each term. Usually, students learn by typical examples (in other words, "paradigms" in the original sense). The process is exemplified in a story of a child who learns that ducks are not swans (etc.) in Kuhn (1977).

Training of scientists take many years. It includes various activities. It certainly includes such experience as watching how the members of the discipline categorize the world, and trying to do so themselves and being corrected.

Different disciplines, or even different schools of a discipline, may use different sets of typical examples. To that extent, conversations between different groups may be unintelligible (or "incommensurable"). When what Y says is certainly false as interpreted with X's lexicon, X may suspect that either Y is utterly incompetent or Y deliberately tells lies. And vice versa, and their social relationship may become broken. But the actual problem may be failure of translation.

We need to share the lexicon beyond one discipline, sometimes beyond the whole scientific community. It is almost impossible for a person to have many occasions of full training to become a disciplinary scientist. So, it is very desiable that each discipline prepare a training kit with which people trained in other disciplines can learn the lexicon. A discipllne needs interpreters of their language in addition to its native speakers.


  • T.S. Kuhn, 1977: Essential Tension. University of Chicago Press. (I read its Japanese translation.)
  • T.S. Kuhn (ed. J. Conant & J. Haugeland), 2000: The Road since Structure. University of Chicago Press. (I read the original English edition.) [My notes about this book in Japanese is here].
  • K.R. Popper, 1959: The Logic of Scientific Discovery. London: Hutchinson. (I read its Japanese translation.)
  • K.R. Popper, 1972: Objective Knowledge. Oxford University Press. (I read its Japanese translation.)