---
title: "Paul Feyerabend"
chunk: 7/12
source: "https://en.wikipedia.org/wiki/Paul_Feyerabend"
category: "reference"
tags: "science, encyclopedia"
date_saved: "2026-05-05T03:36:42.054365+00:00"
instance: "kb-cron"
---

==== Empiricism, pluralism, and incommensurability ====
Much of Feyerabend's work from the late 1950s until the late 1960s was devoted to methodological issues in science. Specifically, Feyerabend offers several criticisms of empiricism and offers his own brand of theoretical pluralism. One such criticism concerns the distinction between observational and theoretical terms. If an observational term is understood as one whose acceptance can be determined by immediate perception, then what counts as 'observational' or 'theoretical' changes throughout history as our patterns of habituation change and our ability to directly perceive entities evolve. On another definition, observation terms are those that can be known directly and with certainty whereas theoretical terms are hypothetical. Feyerabend argues that all statements are hypothetical, since the act of observation requires theories to justify its veridicality.
To replace empiricism, Feyerabend advances theoretical pluralism as a methodological rule for scientific progress. On this view, proliferating new theories increases the testability of previous theories that might be well-established by observations. This is because some tests cannot be unearthed without the invention of an alternative theory. One example Feyerabend uses repeatedly is Brownian motion which was not a test of the second law of classical thermodynamics. To become a test, it must be first explained by an alternative theory – namely, Einstein's kinetic theory of gases – which formally contradicts the accepted theory. By proliferating new theories, we increase the number of indirect tests of our theories. This makes theoretical pluralism central to Feyerabend's conception of scientific method.
Eventually, Feyerabend's pluralism incorporates what he calls the "principle of tenacity." The principle of tenacity allows scientists to pursue theories regardless of the problems it may possess. Examples of problems might include recalcitrant evidence, theoretical paradoxes, mathematical complexity, or inconsistency with neighboring theories. Feyerabend learned of this idea from Kuhn, who argued that without tenacity all theories would have been prematurely abandoned. This principle complements the "principle of proliferation", which admonishes us to invent as many theories as possible, so that those invented theories can become plausible rivals.
In his "Empiricism, Reduction, and Experience" (1962), Feyerabend outlines his theory of incommensurability. His theory appears in the same year as Thomas Kuhn's discussion of incommensurability in The Structure of Scientific Revolutions, but the two were developed independently. According to Feyerabend, some instances of theory change in the history of science do not involve a successor theory that retains its predecessor as a limiting case. In other words, scientific progress does not always involve producing a theory that is a generalization of the previous theory. This is because the successor theory is formally inconsistent with the previous theory attempting to explain the same domain of phenomena. Moreover, the two theories do not share the same empirical content and, therefore, cannot be compared by the same set of observation statements. For example, Buridan's impetus principle has no analogue in classical mechanics. The closest analogue would be momentum, but the two notions are qualitatively distinct (impetus causes motion whereas momentum is the result of motion). Furthermore, Feyerabend claims that there can be no 'parallel notion' of impetus that is explicable within classical mechanics. Any parallel notion that gives non-zero values must assume that inertial movements happen in a resisting medium, which is inconsistent with the assumption in classical mechanics that inertial motion happens in empty space. Therefore, "the concept of impetus, as fixed by the usage established in the impetus theory, cannot be defined in a reasonable way within Newton's theory [since] the usage involves laws... which are inconsistent with Newtonian physics." In response to criticisms of Feyerabend's position, he clarifies that there are other ways in which theories can be compared such as comparing the structures of infinite sets of elements to detect isomorphisms, comparing "local grammars", or building a model of a theory within its alternative.  Incommensurability, however, only arises if scientists make the choice to interpret theories realistically. Theories interpreted instrumentally cannot be incommensurable, on Feyerabend's view.
Feyerabend's pluralism is supported by what he calls the 'pragmatic theory of meaning' which he developed in his dissertation. Here, he explicitly resuscitates Neurath and Carnap's physicalism from the 1930s. According to the pragmatic theory of meaning, language consists of two parts. First, there is the characteristic of a language which is a series of noises produced under specific experimental situations. On Feyerabend's views, human observation has no special epistemic status – it is just another kind of measuring apparatus. The characteristic of a language comes from placing observers in the presence of phenomena and instructing them to make specific noises when a phenomenon is sensed. These noises, to become statements (or parts of a language with meaning), must then be interpreted. Interpretation comes from a theory, whose meaning is given is learned though not necessarily through ostension. Once we have an interpreted characteristic, we have statements that can be used to test theories.