Confirmation holism

In the epistemology of science, confirmation holism, also called epistemological holism, is the view that no individual statement can be confirmed or disconfirmed by an empirical test, but only a set of statements (a whole theory).

It is attributed to Willard van Orman Quine who motivated his holism through extending Pierre Duhem's problem of underdetermination in physical theory to all knowledge claims. Duhem's idea was, roughly, that no theory of any type can be tested in isolation but only when embedded in a background of other hypotheses, e.g. hypotheses about initial conditions. Quine thought that this background involved not only such hypotheses but also our whole web-of-belief, which, among other things, includes our mathematical and logical theories and our scientific theories. This last claim is sometimes known as the Duhem–Quine thesis. A related claim made by Quine, though contested by some (see Adolf Grünbaum 1962), is that one can always protect one's theory against refutation by attributing failure to some other part of our web-of-belief. In his own words, "Any statement can be held true come what may, if we make drastic enough adjustments elsewhere in the system.".

By 1845 astronomers found that the orbit of planet Uranus around the Sun departed from expectations. Not concluding that Newton's law of universal gravitation was flawed, however, astronomers John Couch Adams as well as Urbain Le Verrier independently predicted a new planet, eventually known as Neptune, and even calculated its weight and orbit through Newton's theory. And yet neither did this empirical success of Newton's theory verify Newton's theory.

Le Verrier soon reported that Mercury's perihelion—the peak of its orbital ellipse nearest to the Sun—advanced each time Mercury completed an orbit, a phenomenon not predicted by Newton's theory, which astrophysicists were so confident in that they predicted a new planet, named Vulcan, which a number of astronomers subsequently claimed to have seen. In 1905, however, Einstein's special theory of relativity claimed that space and time are both relative, refuting the very framework of Newton's theory that claimed that space and time were both absolute.

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