Paul Feyerabend (1) unkindly described Karl Popper’s theory of the scientific method as a “small bubble of hot air.”

An examination of Popper’s theory justifies Feyerabend’s judgment.

Although he wrote on the scientific method at considerable length over a period of 60 years, Popper had rather little to say that could be considered fundamental.

His basic idea concerned the role of falsification in science. Thus, for example, he asserted:

In so far as a scientific statement speaks about reality, it must be falsifiable: and in so far as it is not falsifiable, it does not speak about reality. (2)

There is an absurdity in this statement, since taken literally, it means that all scientific statements are false.

But even if one interprets the word falsifiable to mean falsifiable if in fact false, i.e., testable, then Popper’s principle was hardly a novel insight. It has been a while since scientists last invoked mystical entities such as phlogiston, entelechy, and vital force to explain reality. And at least since Einstein’s 1905 paper on special relativity, it has been generally recognized that whatever variables are invoked to account for a phenomenon must be defined operationally, which means defined in such a way as to indicate how they can be observed or measured. And whatever is said about something so defined can be tested, or is falsifiable, to use Popper’s idiosyncratic terminology.

But where Popper parted company with the community of scientists altogether was with his assertion that:

Every genuine test of a theory is an attempt to falsify it, or to refute it. (2)

Every one of the thousands if not millions of university graduates who in recent decades took an elective course in the philosophy of science knows, thanks to Poppper, that falsification of hypotheses is the key task of the scientist and the only means to scientific advance.

Except that it isn’t.

Fortunately, few scientists take university courses in philosophy or read books about the scientific method, or if they do, they keep what the learn thereby strictly compartmentalized from their thinking while at work: for a genuine scientist practices no method.

What guides the scientific investigator is not some dreary system invented by philosophers, but as H.L. Mencken explained:

a boundless, almost pathological thirst to penetrate the unknown, to uncover the secret, to find out what has not been found out before … [the scientific investigator is like] a dog sniffing tremendously at an infinite series of rat-holes.

Which means that science is not solely, or even mainly, about testing theories. Much of it is just about finding things out, i.e., making new observations. As this is written*, a recent issue of Science Magazine carries an article (3) entitled The Precise Solar Shape and Its Variability, which begins with the words “The precise shape of the Sun has not been convincingly determined,” and goes on to show that the Sun is, in fact, not spherical as you may have thought, but oblate!

See: no theory, just an observation, though with interesting theoretical implications. Meantime, the Proceedings of the US National Academy of Sciences just reported a study (4) explaining how the arrangement of layers of rod-shaped cellulose fibers in the skin of the fruit of the African perennial herb Pollia condensata, give the fruit a vivid iridescent blue coloration despite the absence in the tissue of pigments, i.e., another piece of clever and instructive observation.

Much of science, in fact the great majority, is the same, and without it the theorists would be without work.

But if a scientists has a theory, the last thing they wish to see is their theory refuted. And although disproofs of theories constitute important landmarks in the advancement of science, science cannot progress solely by refutation of errors: it must construct. Thus the most exciting developments in science are reports not of theories that failed but of tests that interesting theories have survived.

If Eddington’s 1919 expedition to the tropics to measure the curvature of starlight by the gravitational attraction of the sun during a total solar eclipse had yielded conclusively negative results, both the expedition and the theory of special relativity would long since have been forgotten. The importance of the expedition was precisely that it did not falsify Einstein’s theory, or as most people with less philosophical exactitude would say, Eddington’s observation proved Einstein’s theory (although it may not have done, but that is another matter).

True special relativity may eventually be proved more or less incorrect in some details or even in its entire theoretical basis. But within the domains in which it has been tested, we know it is a theory of practical validity because it gives valid predictions, just as Newton’s theory of gravitation, within the domains in which it is normally used, gives valid results despite having been superseded by Einstein’s more general theory of gravitation.

In other words, contrary to Popper’s cock-eyed notion, what we think we know of science is, for the most part, correct as a description of the world. And even if many of the theoretical underpinnings of science are proved wrong, the laws of science so far uncovered, for example, Maxwell’s equations of classical electrodynamics, the gas laws or the periodic table, will nevertheless remain valid descriptions of reality.


(1) Feyerabend, P. 1987. Farewell to reason. Verso, London, 1987.
(2) Popper, K.R. The logic of scientific discovery, Hutchinson, London, 1959.
(3) Kuhn, J.R. et al. 2012. The precise solar shape and its variability. Science, 337: 1638-1640.
(4)Vignolini, Silvia, et al. 2012. Pointillist structural color in Pollia fruit. PNAS, 109: 15712-15715.

* First published October, 2012.

See also: Floccinaucinihilipilification: Popperian poppycock as a theory of science