The aim of this paper is to describe a methodology for revising logical principles in the light of empirical psychological findings. Historical philosophy of science and wide reflective equilibrium in ethics are considered as providing possible models for arguing from the descriptive to the normative. Neither is adequate for the psychology/logic case, and a new model is constructed, employing criteria for evaluating inferential systems. Once we have such criteria, the notion of reflective equilibrium becomes redundant.

It is in the scholium of thePrincipiaon time, space, place and motion that Newton delivers what is — arguably — a reluctant kiss of betrayal to empiricism. Right there, ‘in the main body of his chief work,’ as E.A. Burtt observes, the deed is done: ‘When we come to Newton's remarks on space and time … he takes personal leave of his empiricism.’ Reichenbach registers the event less charitably, dismissing the ‘crude reification of space that Newton shares with the epistemologically (...) unschooled mind in its naive craving for realism.’ Injury is then added to insult as Reichenbach holds Newtonian mechanics to task for arresting the analysis of the problems of space and time for more than two centuries. (shrink)

Sometimes a theory is interpreted realistically--i.e., as literally true--whereas sometimes a theory is interpreted instrumentalistically--i.e., as merely a convenient device for summarizing, systematizing, deducing, etc., a given body of observable facts. This paper is part of a program aimed at determining the basis on which scientists decide on which of these interpretations to accept a theory. I proceed by examining one case: the nineteenth-century debates about the existence of atoms. I argue that there was a gradual transition from an instrumentalist (...) to a realistic acceptance of the atomic theory, because of gradual increases in its predictive power, the "testedness" of its hypotheses, the "determinateness" of its quantities, and because of resolutions of doubts about the acceptability of its basic explanatory concepts. (shrink)