Scientific Models in Philosophy of Science

2 Mechanical Models

A    (for example, Jammer 1965, p. 167), the concept of a model started to be used in science in the second half of the nineteenth century. Models were used before that time, yet I take my point of departure from nineteenth-century models because these were the models to which twentieth-century philosophers of science mostly referred when they considered models in science.₁ Whether physically built or hypothetically conceived, early models were mechanical. Being mechanical can mean two different things (cf. Schiemann 1997, pp. 21ff.): 1. Mechanical may mean that a process is explained in terms of the principles of classical mechanics (Newton, Lagrange); or 2. Mechanical may mean that motion is explained in terms of the “pushing” and “pulling” of things, whereby the motion is passed on through direct contact between the things involved (no action at a distance). While the former has its roots in the Philosophiae Naturalis Principia Mathematica (1687) of Isaac Newton (1642–1727), the latter goes back to atomistic philosophies of Leucippus (fifth century ..) and Democritus (around 460–370 ..) and to the seventeenth-century mechanical philosophy of, for example, Pierre Gassendi (1592–1655), 21 S C IENTIFIC M OD E L S M EC H ANIC AL MOD EL S AN AL OGY THEORIE S PARAD IGM S AND M ETAPH ORS THE S EM ANTIC VIE W AND THE S TUDY OF SC IEN TIFIC PR ACTIC E PH EN OM EN A , DATA , AND DATA MODE L S REPRE SE NTATION CONCL USION 1 2 3 4 5 6 7 8 9 Bailer CH2:Layout 1 7/5/09 2:12 PM Page 21 René Descartes (1596–1650), and Robert Boyle (1627–1691). In what follows, I shall use “mechanical” roughly in the second sense, although with some further elaboration. If reference to the first sense needs to be made, I do so by talking about (belonging to) mechanics, meaning classical mechanics. The above distinction between the two uses of “mechanical” is also related to what Thomas Kuhn (1977) has called the mathematical and the experimental tradition of science. The mathematical tradition focuses on principles and deduction, as exemplified in Newton’s Principia , and corresponds to the previous first sense of “mechanical.” The experimental tradition often relies on corpuscularian conceptions and therefore corresponds to the previous second sense of “mechanical.” According to Kuhn’s account, in antiquity the physical sciences of astronomy , optics, and statics all belonged more or less to the single field of mathematics. Data collection was uncommon, and these disciplines relied mostly on casual observations, besides mathematics. Kuhn names Galileo, Kepler, Descartes, and Newton as important seventeenthcentury figures who all partook in this mathematical tradition of doing science and who at the same time had “little of consequence to do with experimentation and refined observation” (Kuhn 1977, p. 40).² Kuhn contrasts this with experimental or “Baconian” science. The new experimental fields of research often had their roots in crafts and did not have the theoretical backup of the classical, mathematical sciences . Chemistry, for instance, had been the domain of pharmacists and alchemists. Mathematics was not perceived to play as much a role in these new areas of experimental investigation as it did in the classical sciences. The experimentalists were often amateurs with little mathematical skills, but adherents to corpuscularian ideas. Isaac Newton, as Kuhn highlights, presents an exception with regard to this separation in that he participated in and inspired both traditions: the mathematical tradition with the work of the Principia and the experimental, corpuscularian tradition with the work of the Opticks, or a Treatise of the Reflections, Refractions, Inflections, and Colours of Light (first published in 1704).³ As a work about materials and their structure (and not just their motion and the production of motion by forces), the Opticks stood in the mechanical tradition of corpuscularian theories (Cohen 1956, p. 121). Thus it was not so much about mathematical principles. 22 Mechanical Models Bailer CH2:Layout 1 7/5/09 2:12 PM Page 22 Accordingly, the nineteenth century saw diverging trends, the mathematization of the experimental sciences on the one hand (section 2.1) and the employment of mechanical models on the other (section 2.2). Perhaps because models stood in stark contrast to the wellaccepted mathematical trend, models prompted the need for explication or even promotion by their avid users. In section 2.3, I discuss some nineteenth-century considerations...