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Anik Waldow on ‘Jean Le Rond d’Alembert and the experimental philosophy’

Anik Waldow writes …

Peter Anstey’s essayJean Le Rond d’Alembert and the experimental philosophy” sets out to confirm his claim that the distinction between experimental philosophy and speculative philosophy “provided the dominant terms of reference for early modern philosophy before Kant” (p.1) by examining the Preliminary Discourse of the Encyclopédie.  Anstey comes to the conclusion that d’Alembert, who identified metaphysical speculation as the reason why experimental science had “hardly progressed” (p.3), was highly influenced by Locke and clearly reflected Newton’s anti-hypothetical stance.

The paper contains two major lines of argument, which are interconnected but possess slightly different focuses. The first is concerned with the correction of our understanding of particular philosophers and their commitment to the experimental tradition of Locke, Boyle and Newton. The second intends to alter the way we approach the history of philosophy. In this context Peter’s discussion of d’Alembert amounts to a defense of a new conceptual scheme that ought to replace the rationalist/empiricist distinction, thus enabling us to correct our knowledge of early modern philosophy in general. I will merely focus here on the first of these two points, leaving my worries concerning Anstey’s suggestion that Newton’s own experimental practice is able to clearly demarcate the line between experimental and speculative natural philosophy for another occasion.

Much of Anstey’s essay hinges on the claim that d’Alembert’s own rational mechanics is not hostile to experimentalism, but “an extreme application of the new Newtonian mathematical method that came to predominate the manner in which the experimental philosophy was understood in the mid-eighteenth century.” (p. 12) Rational mechanics is a discipline committed to an a priori methodology that seems to be diametrically opposed to the inductive practice of the experimenter and her strict quantitative treatment of observable phenomena. And even though one may argue that experiments are in some restricted sense relevant to rational mechanics, it is clear that this discipline is not committed to the kind of “systematic collection of experiments and observations” (Preliminary Discourse to the Encyclopedia of Diderot, trans and intro. Richard N. Schwab, Chicago,1995, p.24) that d’Alembert regards as the defining feature of experimental physics. To identify d’Alembert as a defender of experimentalism therefore requires Anstey to show that there is no contradiction involved in practising rational mechanics, on the one hand, and defending Lockean experimentalism, on the other.

Anstey’s argument is convincing as long as natural philosophy is treated as a whole that is able to integrate various methodologies. In this form the argument makes a good case against the rigid dichotomies that the rationalist/empiricist distinction introduces, because it shows that we need not endorse what I call an ‘either-or conception’ of experimentalism: either we are experimenters and reject rational mechanics as a speculative discipline because of its detachment from observable phenomena; or we conceive of natural philosophy as a broadly mathematical enterprise and attack experimentalism for its lack of scientific rigour.

Having said that, however, I should like to raise the following question. How well supported is Anstey’s claim that d’Alembert believed that rational mechanics, and in particular demonstrative reasoning, was not merely compatible with experimentalism, but an integral part of it? The reason I ask this question is that we must distinguish between two positions: the first accepts demonstrative mathematics as a methodology in an area of natural philosophy that, strictly speaking, does not qualify as experimental in itself; the second endorses the claim that all natural philosophy ought to be experimental. Hence, the first position regards experimentalism as a specific branch of natural philosophy, while the second takes the whole of natural philosophy to be committed to the tenets of experimentalism.

By aligning d’Alembert’s own methodology with Newton’s mathematized experimentalism, Anstey suggests that d’Alembert was a proponent of the second position. However, I think that d’Alembert’s conception of rational mechanics as the queen among the various natural philosophical disciplines reveals him to be more inclined to the first position. In thinking of rational mechanics as taking the lead in the generation of natural philosophical knowledge, d’Alembert turns experimentalism (conceived as the systematic collection of experiments and observations) into no more than a useful addition to a natural philosophical practice firmly rested on a priori reasoning. Experimentalism is here appreciated only in so far as it is able to generate solutions to problems where rational mechanics can advance no further. Or slightly differently put, experimentalism is acknowledged for its usefulness, but far from being regarded as the discipline that gives the whole of natural philosophy its tone and direction.

In short, Anstey’s paper may have shown that d’Alembert sympathized with Lockean experimentalism. However, more needs to be said in order to clarify how it is possible to think of rational mechanics as a discipline that is, in and of itself, experimental in spirit. Otherwise it is hard to see why we should agree with Anstey’s claim that d’Alembert thought of the whole of natural philosophy as an essentially experimental discipline.

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