Front Page Titles (by Subject) Reason and Choice - Literature of Liberty, January/March 1978, vol. 1, No. 1
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Reason and Choice - Leonard P. Liggio, Literature of Liberty, January/March 1978, vol. 1, No. 1 
Literature of Liberty: A Review of Contemporary Liberal Thought was published first by the Cato Institute (1978-1979) and later by the Institute for Humane Studies (1980-1982) under the editorial direction of Leonard P. Liggio.
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Reason and Choice
“Incommensurability and the Rationality of the Development of Science.” British Journal for the Philosophy of Science (UK), 28 (1977): 345–350.
Can revolutionary advances in science proceed in a “rational way”? According to Kuhn and Feyerabend such advances proceed in a disconnected way, making it impossible to find logical connections between the old theory and the new theory that replaced it. This position has several flaws.
The Thesis of Incommensurability (TI), recently popularized and defended by Thomas Kuhn and P. K. Feyerabend, maintains that two scientific theories separated by a Kuhnian conceptual “revolution” may be completely “incommensurable.” In other words, TI denies that two successive theories or “paradigms” are rationally comparable; they resemble two completely different languages, organizing the world in such radically different ways that they permit no logical translation. But one can demonstrate that “incommensurability” need not be a stumbling block to methodologists hoping to advance a rational interpretation of the way science works. A solid case exists for those theorists who have tried to find a rational and progressive account of changes in scientific theory, and who are intrepid enough to call such changes a “growth in knowledge” rather than complete discontinuity.
One can level two criticisms at the adherents of TI. The first objection observes that if TI were true it would apply not merely to revolutionary periods but to all periods of theoretical change. However, the champions of TI wish to believe that during periods of “normal” or non-revolutionary science, an improved theory (T') may be rationally comparable or commensurable with the earlier theory (T) from which it developed. This is, of course, true. But according to TI, T and T' would also have to be incommensurable even in these “normal” scientific changes. There is no nonarbitrary way to distinguish between revolutionary and nonrevolutionary periods of scientific development. One reason for this is that historically, new ideas in science often have their greatest or “revolutionary” impact only long after their discovery. Eminent scientists may not know that their discoveries are “revolutionary”; their “normal” science work may later have “revolutionary” implications.
Accordingly, TI faces a dilemma: either it excludes rational comparisons between theories in nonrevolutionary cases, or it must allow comparison in revolutionary cases.
The second critique against TI rests on a historical fact. A “relation of correspondence” holds between successive theories and we may formulate it in purely formal terms, even when the two theories are “incommensurable” in the sense that they invest the same terms with different meanings (meaning-variance). Contrary to TI, the character of this correspondence relation allows for a rational and logical continuity in the development of science. One can exhibit this continuity in terms of logical relations among successive theories. Historically, working scientists consciously use such heuristic tools as the principle of correspondence to lead them logically and intuitively to new discoveries. Scientists do not function according to TI.