Intelligibility in Science

I. Introduction

The central issue that I want to address is that of "intelligibility" in the history of science. By using this term, however, I do not mean to imply simply an enterprise of analyzing more-or-less coherent conceptual structures, so as to be able to say that people believed a particular doctrine either because it was "consistent" with other ideas that they held, or else because it was strategically useful to them in the particular contexts in which it was deployed. Instead, my aim is to find a way of getting at the roots of brute intelligibility itself: in other words, at the ways in which people find that something makes sense. This concern relates, of course, to notions of what constitutes a satisfactory explanation, but it centrally focuses on issues rather more fundamental than the formalistic structures of explanation.

A useful clarification comes from a consideration of Thomas Kuhn's ideas relating to the issue of incommensurability. Paradigms, in the form of what he later called "disciplinary matrices," were ways of talking about the interconnectedness of concepts and associated practices in general, while the notion of incommensurability appears most clearly in the terms of Mary Hesse's later "network model," where the meaning of any particular concept is determined in relation to other concepts linked to it in the network.¹ The Kuhnian incommensurability of apparently similar concepts in successive paradigms, such as "mass" for Newton versus "mass" for Einstein, rests on the fact that the concept in Newtonian mechanics means something different from the concept in relativistic mechanics due to its being defined in relation to a different network.²

Kuhnian (or Feyerabendian)³ incommensurability is a notion that is clearly explicable in formal terms, and it is that formalistic understanding that rather sidesteps the issue that particularly concerns me here. When someone operating under the Einsteinian relativistic "paradigm" understands "mass" in a way different from that of someone operating within a Newtonian paradigm, the difference is in principle explicable and analyzable. Nonetheless, Kuhn wanted to represent matters rather more strongly. For him, people seeing things from the vantage point of different paradigms really cannot properly see things in the same way, even by analyzing conceptual networks—and yet Kuhn's position finally rests on just such an argument. It is on this problem of apparent unanalyzability that I want to focus in talking about "intelligibility" in science.

In the history of science, one routinely finds that what counts as a satisfactory type of explanation at one period, or for one group of people, sometimes fails to count as satisfactory at another time, or for another group. For example, when Isaac Newton developed the idea of universal gravitation in the late seventeenth century, many mathematicians and philosophers, especially in continental Europe, criticized him for not having given a satisfactory explanation of why the planets move as they do—or why apples fall. They reckoned that he had given only a mathematical description of their motion (invoking some indeterminate sort of action-at-a-distance), rather than a physical explanation. For these critics, the purpose of natural philosophy—which was the enterprise that Newton claimed to be pursuing—should properly be an explanatory, not just a descriptive, one. Such critics, including Christiaan Huygens, held that a physical explanation should mean a strictly mechanical one—by which they meant direct contact-action of matter pushing on matter, whether by collision or pressure.⁴

Subsequently, during the course of the eighteenth century, natural philosophers gradually became accustomed to the idea of action-at-a-distance; thus, talking in its terms in practice came to constitute a satisfactory explanation, regardless of the earlier objections. Later, the situation again changed: for people such as James Clerk Maxwell and other British physicists in the nineteenth century, a satisfactory explanation of gravity, and of other phenomena where forces are apparently communicated across space, could properly be couched only in terms of material contact-action, using a mechanical aether that filled all...