The Genealogy of Genealogy (II): Diderot and the Pursuit of Truths

Recall that in Letters to Serena (1705), Toland’s genealogical method is a debunking enterprise; it is applied only to concepts whose truth cannot be secured by natural methods of inquiry. (Toland graciously or prudentially allows that revelation may secure truth.) In Toland-style ‘genealogy’ a concept is treated "like some others in philosophy, had a beginning at a certain time, or from a certain author who was the inventor thereof, and which was favoured or opposed as peoples' persuasion, interest or inclination led them." I have been unable to find an instance where Toland applies this genealogical method to concepts whose truth, if any, can be secured by natural methods. This move was left to Diderot (also to Adam Smith, but he delayed publication of his History of Astronomy by half a century).

At the start of Diderot’s (1754) Thoughts on the Interpretation of Nature, Diderot offers a ‘natural history’ of each of the individual sciences; he treats “geometry,” by which Diderot means – judging from the names he associates with it (e.g., “Bernoulli, Euler, Maupertuis, Clairaut, Fontaine, and D’Alembert”) – mathematical physics or, especially, rational mechanics, as the exemplary science. In section 5, Diderot divides the life-cycle of a science into three stages: (i) a "birth;” (ii) a period of high prestige; and (iii) a decaying period when there are diminishing returns of enquiry within it. Finally, there is (iv) the completed edifice—confusingly, already discussed in the previous section (4; all my references below are to sections).

Now, on first reading (of section 5) it might seem that through these four stages Diderot is primarily interested in tracking the interconnection among (a) the social status of a discipline and (b) the character types to be found within each discipline at (c) each stage. In the early, exciting stages heterogeneous characters are drawn into a science, but at later stages as opportunities dwindle the character types to be found in a science are also winnowed down. But, a second point of Diderot’s analysis (which one discerns by reading sections 4-5 jointly) is to demarcate the then-present as a transition-period in which rational mechanics is nearing completion and a number of new sciences, (i.e., “ethics, literature, natural history and experimental physics”) are about to become ‘hot.’ My colleague, Charles Wolfe (the expert on Diderot in the English language philosophy) has convinced me that it is okay to refer to ‘natural history’ with ‘biology;’ with “ethics” Diderot means moral science, that is, the mixture of moral psychology, sociology, political theory, and normative ethics familiar, perhaps, from Adam Smith’s The Theory of Moral Sentiments (1759).

So, Diderot does not fit the myth in which the optimistic (or radical) French Enlightenment is tied closely to the development and advocacy of Newtonian physics. (Some other time I will discuss how both Toland and Diderot echo Spinozistic and Mandevillian anti-mathematics.) This is not because Diderot shares Rousseau's reservations about Enlightenment and science; Diderot is clearly an advocate of science--just not the variety of rational mechanics that is being developed around him. By Diderot's lights, rational mechanics is too far removed from reality to be useful and welfare enhancing. He advocates that resources be devoted to splendid, and more useful human directed sciences (medicine, agriculture, political economy, etc.) with full recognition that "in a few centuries" (6) they, too, will eventually decay and terminate.

But Diderot is explicit that the appeal to utility is political; he believes that such an appeal is the "only" way of "truly recommending philosophy in the eyes of" the public (literally the "vulgar" (19)). In fact, in this context, Diderot distinguishes between public enlightenment and philosophical enlightenment ("éclaire le philosophe" (19)). The former is driven by utility, while the latter is adamantly not. At this point one would expect a resounding (and, perhaps, elitist) vindication of the intrinsic worth of the pursuit of truth. Instead Diderot claims "the understanding of the philosopher is often lit by what harms, and darkened by what is useful," ("puisque l'entendement du philosophe est souvent éclairé par ce qui nuit, et obscurci par ce qui sert" (19)). The door has been opened to an internal, genealogical critique of philosophy.  

PS In preparing this post I have consulted a translation by David Adams, although I have chosen to use my own.