Thomas Kuhn is perhaps the best known philosopher of science. He claimed that the advance of scientific knowledge proceeds in discontinuous breaks that he called "revolutions" and which came to be known as "paradigm shifts."

Kuhn suggested that basic scientific concepts and language terms that describe them change their meanings across these breaks, producing an incommensurability of ideas that make communications between scientists working in different paradigms difficult or even impossible.

Kuhn is simply wrong about this. Any conceptual idea about any structure or process in the world that changes in a Kuhnian revolution can be described in the language terms used before and after the revolution by scientific experts who can provide an adequate translation between the terms.

Kuhn came of age when analytic language philosophers were abandoning the logical positivism of Bertrand Russell and the early Ludwig Wittgenstein and their "truth tables." Even the logical empiricists of the Vienna Circle in Europe, with their theory that science advances by "verification" of observations came under attack.

Kuhn's most famous work, The Structure of Scientific Revolutions, first appeared as an article in the International Encyclopedia of Unified Science, a publication of the Vienna Circle.

In philosophy of science, the logical empiricists were challenged by Karl Popper, who insisted that scientific theories stand and fall not on verification, but on his criterion of "falsification." This was flawed. Falsification is just a negative verification, equally likely to be overthrown by future scientific evidence. And all scientific theories rest on experimental evidence, not logical "proofs."

Analytic language philosophy itself had a revolution against the logical "truth" of all knowledge, that all facts could be built up from "atomic facts." just as all matter is built up from atoms. Wittgenstein thought that language provided a "picture theory" of the world, that sentences can be framed as formal "propositions" like those in the great Principia Mathematica of Russell and Alfred North Whitehead. All mathematics and then all of science could be based upon these "logical atoms." This too was flawed.

Behind this was the great philosophical and ultimately theological idea that the world and the universe are rationally constructed, so its structure can be understood by reason alone. This is called modernism, over against the idea of tradition, that knowledge is simply handed down from generation to generation by authorities. The first modern theology was Thomas Aquinas and other scholastics, who claimed revelation and reason could be reconciled. The first modern philosopher was René Descartes, whose work led to the age of enlightenment and the "laws" of modern science..

Modernists believe that reason can establish or "grounded" objective knowledge. Kuhn questioned the existence of "objective" knowledge, just when many philosophers of science were questioning the idea of an objective physical reality. Albert Einstein's theories of special and general relativity had made "relativism" fashionable in many fields. And quantum mechanics threatened the deterministic implications of classical physics.

Structuralism in linguistics, anthropology, psychology, and the social sciences was the idea that universal structures underlie everything that human beings do, think, perceive, and feel. It gave way to post-structuralism, cultural relativism, and then postmodernism, or deconstruction.

Kuhn was a postmodern, though perhaps a reluctant one, especially in the face of attacks on his idea of incommensurabiity by many scientists and philosophers.

Where Kuhn was right is the idea that scientific progress is not made by works of individual thinkers who establish the objective truth about reality. Truth, especially objective or absolute truth, is a concept that is essential in mathematics and logic. The meaningful equivalent in science is the statistical evidence supporting various theories.

Kuhn properly located progress in science in the scientific community as a whole. He saw the community of scientists as having only individual "subjective" positions. All "objective" knowledge is ultimately the result of "subjective," culturally biased, views of the individual scientists. "Objective" science is impossible

Concerns about objectivity had been thought through in an earlier century by perhaps the greatest ever philosopher of science, Charles Sanders Peirce. He described a "community of inquirers" who could achieve "intersubjective agreement" in the long run. For Peirce, this agreement would be an approach, perhaps only asymptotic, to something like scientific "truth."

Better than any other philosopher, Peirce articulated the difference between a priori probabilities and a posteriori statistics. He knew that probabilities are a priori theories and that statistics are a posteriori empirical measurements, the results of observations and experiments.

The "truth" of any scientific theory is therefore always provisional, subject to change or incorporation into a larger, more comprehensive theory that explains all past evidentiary facts as well as newly discovered facts in the future.

With Peirce in mind, we see that all science, like all knowledge (our SUM), is a living thing that is still growing.