This paper defends a realist interpretation of theories and a modest realism concerning the existence of quantities as providing the best account both of the logic of quantity concepts and of scientific measurement practices. Various operationist analyses of measurement are shown to be inadequate accounts of measurement practices used by scientists. We argue, furthermore, that appeals to implicit definitions to provide meaning for theoretical terms over and above operational definitions fail because implicit definitions cannot generate the requisite descriptive content. The (...) special case of establishing a temperature scale is examined to show that nonrealist accounts fail to provide insight into the theoretical connections that scientific laws postulate to hold among quantities. (shrink)

1. Introduction. Professor Nagel's account of the “cognitive status” of scientific theories has been attacked by P. K. Feyerabend [5] and M. B. Hesse [8] in terms of his alledgedly misguided distinction between experimental laws and theories. The difficulty lies, these critics agree, in Nagel's attempt to find a stable basis for scientific theories in an observational basis of experimental laws. Both Feyerabend and Hesse note the vacillation in Nagel's account of the stability of the meaning of experimental terms and (...) in his discussion of the status of observational as opposed to theoretical terms. They find Nagel too “positivistic” and see as a first step toward a more adequate account of scientific theories the abandonment of the theoretical-observational dichotomy as having more than a pragmatic significance. Nagel's discussion of the theoretical-observational dichotomy is, I agree, inadequate in certain respects. I shall, however, suggest a quite different remedy from those of Feyerabend and Hesse, one that depends neither on a phenomenalistic reduction of theoretical entities nor on a blurring of the theoretical-observational dichotomy. (shrink)

Recent philosophical discussions have failed to clarify the roles of the concept fitness in evolutionary theory. Neither the propensity interpretation of fitness nor the construal of fitness as a primitive theoretical term succeed in explicating the empirical content and explanatory power of the theory of natural selection. By appealing to the structure of simple mathematical models of natural selection, we separate out different contrasts which have tended to confuse discussions of fitness: the distinction between what fitness is defined as versus (...) what fitness is a function of, the contrast between adaptedness as an overall property of organisms and specific adaptive capacities, the distinction between actual and potential reproductive success, the role of chance versus systematic causal relations, fitness as applied to organisms as opposed to fitness applied to genotype classes, heritable adaptive capacities of genotypes as opposed to relations between genotypes and the environment. We show how failure to distinguish and properly interrelate these different aspects of “fitness” adds confusion to a number of already complex issues concerning evolutionary theory. On the basis of our discussion of these different aspects of “fitness”, we propose a terminology which makes the necessary distinctions. A central result of our analysis is that the concept of fitness as the overall adaptedness of organisms does not enter into the causal structure of evolutionary explanation, at least to the extent that this structure is represented in the mathematical models of natural selection. (shrink)