Last time we discussed the transition from pre-paradigmatic science to paradigmatic or "normal" science, and what that involves. Specifically, we discussed the nature and role of a paradigm, distinguishing between the primary, narrow sense of the term (an exemplar, i.e., a definitive, concrete achievement) and a broader sense of the term (a disciplinary matrix or framework, which includes conceptual, methodological, metaphysical, theoretical, and instrumental components). We also noted that though Kuhn usually talks about each scientific discipline (as distinguished roughly by academic department) as having its own paradigm, the notion is more flexible than that and can apply to sub-disciplines (such as Freudian psychoanalysis) within a broader discipline (psychology). The question of individuating paradigms is a difficult one (though Kuhn sometimes speaks as if it's a trivial matter to identify a paradigm), but we will not investigate it any further. Now we want to turn to how paradigms lead to their own destruction, by providing the framework necessary to discover anomalies, some of which lead to the paradigm's downfall.

As you recall, normal science is an enterprise of puzzle-solving according to Kuhn. Though the paradigm "guarantees" that the puzzles it defines have solutions, this is not always the case. Sometimes puzzles cannot admit of solution within the framework (disciplinary matrix) provided by the paradigm. For example, the phlogiston theory of combustion found it difficult to explain the notion of weight gain when certain substances were burned or heated. Since combustion was the loss of a substance on that view, there should be weight loss. This phenomenon was not taken to falsify the theory, however (contrary to what Popper might claim); instead, phlogiston theorists attempted to account for the difference by postulating that phlogiston had "negative mass," or that "fire particles" sometimes entered an object upon burning. The paradigm eventually collapsed for several reasons:

• None of the proposed solutions found general acceptance; i.e., there was a multiplicity of competing solutions to the puzzle presented by the anomaly (weight gain).
• The proposed solutions tended to create as many problems as they solved; one method of explaining weight gain tended to imply that there would be weight gain in cases in which there was none.
• This led to a sense of crisis among many practitioners in the field; the field begins to resemble the pre-paradigmatic stage (i.e., nearly random attempts at observation, experimentation, theory formation), signaling the demise of the old paradigm. Nevertheless, it is not abandoned: to abandon it would be to abandon science itself, on Kuhn's view.
• Eventually, a competitor arose that seemed more promising than any of the other alternatives, but which involved a substantial conceptual shift. This was the oxygen theory of combustion.
  

Paradigm Change as Non-Cumulative

There is a common but oversimplified picture of science that sees it as a strictly cumulative enterprise (science progresses by finding out more and more about the way the world works). The "more and more" suggests that nothing is lost. Kuhn argues that on the contrary there are substantial losses as well as gains when paradigm shifts occur. Let's look at some examples.

• Some problems no longer require solution, either because they make no sense in the new paradigm, or they are simply rejected.
• Standards for evaluating scientific theories alter along with the problems that a theory must according to the paradigm solve.

Example: Newtonian physics introduced an "occult" element (forces), against the prevailing view of the corpuscular view that all physical explanation had to be in terms of collisions and other physical interactions between particles. Newton's theory did not accord with that standard, but it solved many outstanding problems. (Corpuscular view could not explain other than in a rough qualitative way why planets would move in orbits; Kepler's Laws were separate descriptions of why this was so. Thus it was a great achievement when postulating forces led to the derivation of Kepler's Laws.) "Forces" were perceived by many as odd, "magical" entities. Newton himself tried to develop a corpuscular theory of gravitation, without success, as did many Newtonian scientists who followed him. Eventually, when it became apparent that the effort was futile, the standard that corpuscular-mechanistic explanation was required was simply disregarded, and gravitational attraction was accepted as an intrinsic, unexplainable property of matter.

Another example: Chemistry before Dalton aimed at explaining the sensory qualities of compounds (colors, smells, sounds, etc.). Dalton's atomic paradigm was only suited for explaining why compounds went together in certain proportions; so when it was generally accepted the demand that a theory explain sensory qualities was dropped.

Other examples: (a) Phlogiston. The problems of explaining how phlogiston combined with calxes to form particular metals were abandoned when phlogiston itself was abandoned. The ether (medium for electromagnetic radiation); explaining why movement through the ether wasn't detectable vanished along with the ether. There simply was no problem to be solved. (b) Michelson-Morley experiment. This experiment was first "explained" by Lorenz based on his theory of the electron, which implied that since forces holding together matter were electromagnetic and hence influenced by movement through the ether, parts of bodies contract in the direction of motion when moving through the ether. Relativity explains the contraction, but in a new conceptual framework that does not include the ether.

• Some new entities are introduced along with the paradigm; indeed, only make sense (i.e., can be conceptualized) when introduced as such. (Oxygen wasn't "discovered" until the oxygen theory of combustion was developed.)
• Elements that are preserved may have an entirely different status. (The constant speed of light is a postulate in special relativity theory, a consequence of Maxwell's theory.) Substantive conceptual theses might be treated as "tautologies" (e.g., Newton's Second Law).

The fact that new standards, concepts, and metaphysical pictures are introduced makes the paradigms not only incompatible, but also "incommensurable." Paradigm shift is a shift in worldview.