New tools for theory choice and theory diagnosis

Theory choice can be approached in at least four ways. One of these calls for the application of decision theory, and this article endorses this approach. But applying standard forms of decision theory imposes an overly demanding standard of numeric information, supposedly satisfied by point-valued utility and probability functions. To ameliorate this difficulty, a version of decision theory that requires merely comparative utilities and plausibilities is proposed. After a brief summary of this alternative, the article illustrates how comparative decision theory affords a rational reconstruction of decisions made by exemplary scientists in two cases of theory choice: Buffon’s law and the luminiferous ether. It also offers a rational reconstruction of two cases of theory diagnosis: Mendeleev’s anomalies and the Pioneer anomaly.     

Semiconduction theory

Conclusions The semiconducting properties of biomacromolecules are a certainty which cannot be neglected when models are proposed for explaining some biological function such as, enzymatic activity of cytochrome oxidase, olfactory transduction, visual reception, properties of the cellular membranes, etc.^6,7,9. Although a perfect correlation does not yet exist between the results of molecular orbital calculations and experimental data regarding the electrical conduction in proteins and nucleic acids⁹, a profound study on the aspects connected with intrinsic mechanisms of conduction in biomacromolecules, as well as on dependence of electrical properties on the impurities acting in vivo, should increase our understanding of biophysical phenomena.     

Kirchhoff's theory of rods

Communicated by C. Truesdell     

Probability in GRW theory

GRW theory postulates a stochastic mechanism assuring that every so often the wave function of a quantum system is ‘hit’, which leaves it in a localised state. How are we to interpret the probabilities built into this mechanism? GRW theory is a firmly realist proposal and it is therefore clear that these probabilities are objective probabilities (i.e. chances). A discussion of the major theories of chance leads us to the conclusion that GRW probabilities can be understood only as either single case propensities or Humean objective chances. Although single case propensities have some intuitive appeal in the context of GRW theory, on balance it seems that Humean objective chances are preferable on conceptual grounds.     

A pre-euclidean theory of proportions

Communicated by B. L. van der Waerden     

Norton's material theory of analogy

In his book, The Material Theory of Induction, Norton argues that the quest for a universal formal theory or ‘schema’ for analogical inference should be abandoned. In its place, he offers the “material theory of analogy”: each analogical inference is “powered” by a local fact of analogy rather than by any formal schema. His minimalist model promises a straightforward, fact-based approach to the evaluation and justification of analogical inferences. This paper argues that although the rejection of universal schemas is justified, Norton's positive theory is limited in scope: it works well only for a restricted class of analogical inferences. Both facts and quasi-formal criteria have roles to play in a theory of analogical reasoning.     

Conceptual dimensions of theory appraisal

After arguing that Laudan's account of the role of conceptual considerations in theory appraisal is inadequate and unsatisfying in a number of respects, I suggest some of the ways in which we might move to develop an alternative account. This alternative presupposes a problem-solving methodology and, unlike the Laudanian approach, awards a crucial role to empirical research in the resolution of the conceptual problems troubling a theory. Three ways in which a theory may enhance the conceptual resources which it supplies for empirical problem-solving are considered: the fine-tuning of theoretical concepts; the appropriation of the conceptual resources of theories in other domains; and the achievement of greater consilience. Reference is made to several historical cases in which such enhancement actually occurred.