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Tag Archives: French philosophy

René Réaumur and Charles Dufay on Experimental Natural Philosophy

A guest post by Michael Bycroft, a PhD Student at Cambridge.

Michael Bycroft writes…

René Réaumur

In a recent post Peter Anstey asked: “When did the French embrace experimental philosophy?” In this post I want to do two things. One is to draw attention to two Frenchmen who practised experimental natural philosophy (ENP) well before Jean-Antoine Nollet began teaching this method in the mid-late 1730s. These men were René Réaumur and Charles Dufay. My other task is to try to explain why these men, who did so much to practice ENP, did so little to explicitly define or defend their practice.

René Réaumur (1683-1757) was arguably the most active and influential member of the Académie des Sciences in the first half of the eighteenth century. Nowadays he is known for his research on insects, steel-making, and thermometry, but his interests were truly encyclopaedic. Charles Dufay (1698-1739) is known to historians of physics as a student of electricity, but his research interests were nearly as broad as those of Réaumur, his patron and collaborator.

There is no doubt that these two men practiced ENP. It is true that they were Cartesians, in the sense that their chief theoretical resources were vortices and subtle fluids. But they wore their theory lightly, and they saw themselves primarily as experimenters rather than as system-builders. This pair was at least as committed to ENP, and in some cases more so, than their French colleague Nollet or their English counterparts Francis Hauksbee the Elder and John Desaguliers.

Yet it is hard to find clear, succinct, accessible endorsements of the key tenets of ENP in the writings of Dufay and Réaumur. Such endorsements do exist, but they are invariably buried in the middle of one or other of the many papers they published in the Académie’s journal, the Mémoires de l’Académie Royale des Sciences. Here is an example from one of Réaumur’s first papers, on the growth of shells, published in the 1709 volume of the Mémoires:

    But conjectures such as these [ie. the ones Réaumur had just advanced in the first part his paper] are not enough in true natural philosophy. Experiments performed on the matters at hand are the only sound basis for our reasoning…It is to experiments that I shall turn to decide whether I have correctly described the manner in which nature behaves, or whether [instead] everything I have said is merely a trick of the imagination.
    Mais de pareilles conjectures ne suffisent point en bonne Physique. Les seules expériences faites sur les choses dont il est question, y doivent servir de bases à nos raisonnemens. … C’est aux experiences que je vais rapporter à faire voir, si j’ai véritablement décrit la maniere dont la Nature agit, ou si l’on doit regarder tout ce qu’on vient d’avancer comme un simple jeu d’imagination.

Charles Dufay

This statement is clearly in the spirit of ENP, and similar statements can be found elsewhere in Réaumur’s papers, and in Dufay’s. But they are fleeting asides rather than stand-alone manifestos. Why were these men so reticent?

An important part of the answer is that the stand-alone manifestos of Nollet, Hauksbee and Desaguliers appear in the prefaces of their natural philosophy textbooks, and Dufay and Réaumur did not write textbooks. They did not need to. They were independently wealthy, drew sizeable pensions from the Academy, and were well-rewarded by the state for their research on French industries such as steel and textiles.

Perhaps it is also relevant that Bernard le Bovier de Fontenelle, the Perpetual Secretary of the Academy, did much to define and defend the Academy’s activities on behalf of its members.

Another factor may be that Dufay and Réaumur were more concerned to defend the application of natural philosophy to industry (against skeptical artisans and ministers) than they were to defend the application of experiment to natural philosophy (against speculative philosophers). At any rate, the former concern dominated the preface to Réaumur’s first book, L’art de convertir le fer en acier (1722).

Finally, as we have seen, Dufay and Réaumur dispensed methodological advice in the course of the papers they published in the Academy. Perhaps they considered this the best forum for expressing their views on ENP, even though this choice makes their views harder for the historian to identify than if they had written textbooks or dictionary entries instead.

This is not to say that Dufay and Réaumur had no connections with earlier and later textbook writers on ENP in France. On the contrary. They both learned much of their physics from Jacques Rohault’s Traité de physique, and in their turn they taught Nollet much of what he knew about experimentation (Nollet assisted both Dufay and Réaumur in their laboratories in the early 1730s). These connections reinforce the broader lesson of this post, which is that the leading practitioners of ENP were not always its most explicit promoters.

Emilie du Châtelet on Hypotheses

Kirsten Walsh writes…

Emilie Du Châtelet (1706-1749) is best known in the popular literature as one of Voltaire’s lovers, but among her contemporaries, she was considered to be a brilliant mathematician, physicist and philosopher, whom Voltaire once described as “a great man whose only fault was being a woman”.  Her work on heat and light predicted infrared radiation, and her translation and commentary of Newton’s Principia, published ten years after her death, is still considered to be the standard French translation.  Today I’m interested in Du Châtelet’s views on hypotheses.

Emilie Du Châtelet (1706-1749)

Du Châtelet’s lengthiest discussion of the use of hypotheses in natural philosophy is found in her Institutions de Physique* (1740), which she wrote as a textbook for her thirteen year old son.  Here, Du Châtelet explicitly set up her position on hypotheses in opposition to both Descartes and the Newtonians.  She saw both positions as too extreme; and neither position as correct or useful.  On the one hand:

    “Descartes, who had established much of his philosophy on hypotheses, … gave the whole learned world a taste for hypotheses; and it was not long before one fell into a taste for fictions.  Thus, the books of philosophy, which should have been collections of truths, were filled with fables and reveries.”

But on the other hand, those who follow Newton “have fallen into the opposite excess”:

    “…he alone, who was able to assign and demonstrate the causes of all that we see, would be entitled to banish hypotheses from physics; but, as for us, who do not seem to be cut out for such knowledge, and who can only arrive at the truth by crawling from probability to probability, it is not for us to pronounce so boldly against hypotheses.”

Du Châtelet advocated a more moderate position.  She thought that hypotheses performed several important functions:

Firstly, hypothesising is a good way to get the proverbial ball rolling.  She wrote:

    “There must be a beginning in all researches, and this beginning must almost always be a very imperfect, often unsuccessful attempt.  There are unknown truths just as there are unknown countries to which one can only find the good route after having tried all the others.  Thus, some must run the risk of losing their way in order to mark the good path for others; so it would be doing the sciences great injury, infinitely delaying their progress, to banish hypotheses as some modern philosophers have.”

Secondly, hypotheses can provide useful explanations of the phenomena:

    “When certain things are used to explain what has been observed, and though the truth of what has been supposed is impossible to demonstrate, one is making a hypothesis.  Thus, philosophers frame hypotheses to explain the phenomena, the cause of which cannot be discovered either by experiment or by demonstration.”

So, unlike Newton, Du Châtelet thought that, if we couldn’t obtain certainties, then we should make do with probabilities:

    “The true causes of natural effects and of the phenomena we observe are often so far from the principles on which we can rely and the experiments we can make that one is obliged to be content with probable reasons to explain them.  Thus, probabilities are not to be rejected in the sciences, not only because they are often of great practical use, but also because they clear the path that leads to truth.”

Thirdly, hypotheses suggest new experiments:

    “Hypotheses must then find a place in the sciences, since they promote the discovery of truth and offer new perspectives; for when a hypothesis is once posed, experiments are often done to ascertain if it is a good one, experiments which would never have been thought of without it.”

Moreover, Du Châtelet thought that experimental results could increase the probability of the hypothesis:

    “If it is found that these experiments confirm it, and that it not only explains the phenomenon that one had proposed to explain with it, but also that all the consequences drawn from it agree with observations, its probability grows to such a point that we cannot refuse our assent to it, and that is almost equivalent to a demonstration.”

However, Du Châtelet warned her readers that, when hypothesising, one must proceed with caution:

    “Without a doubt there are rules to follow and pitfalls to avoid in hypotheses.  The first is, that it not be in contradiction with the principle of sufficient reason, nor with any principles that are the foundations of our knowledge.  The second rule is to have certain knowledge of the facts that are within our reach, and to know all the circumstances attendant upon the phenomena we want to explain.”


    “Since hypotheses are only made in order to discover the truth, they must not be passed off as the truth itself, before one is able to give irrefutable proofs.”

So finally:

    “With this precaution one does not run the danger of taking for certain that which is not; and one inspires those who follow us to correct the faults in our hypotheses and to provide what they lack to make them certain.”

Du Châtelet greatly admired the British philosophers, Locke and Newton in particular.  But her views on hypotheses have much more in common with her fellow Continental philosophers, Leibniz and Wolff.


*Translations are quoted from Du Châtelet, E. (2009), Selected Philosophical and Scientific Writings, J. P. Zinsser (ed.), I. Bour & J. P. Zinsser (trans.), University of Chicago Press.

Daunou and the Fate of Experimental Philosophy in Nineteenth-Century France

Alberto Vanzo writes…

On this blog, we have often stressed the importance of the movement of experimental philosophy between the 1660s and ca. 1800. What happened to this movement in the nineteenth century? Last week Juan noted that, after 1823, the entry “experimental philosophy” in the Encyclopedia Britannica was substantially shortened and then removed. This suggests that that notion may have disappeared from the British philosophical scene. Something similar had happened in Germany, where the tradition of experimental or, as it was mostly called, observational philosophy was eclipsed by Kantian and post-Kantian systems around 1800. The expression “observational philosophy” seems to have disappeared from the German philosophical vocabulary in the early nineteenth century.

In this post, I will highlight an exception to this trend: Pierre-Claude-François Daunou’s Recherches sur les systèmes philosophiques applicables à l’historie. This is the text of the lectures on the history of philosophy that Daunou gave at the Collège de France in 1829-1830. It was published posthumously in 1849. In this work, as late as in the mid-nineteenth century, we find a wholehearted defense of experimental philosophy and its application to philosophical historiography.

Daunou aims to outline a philosophical history of philosophy. What renders the history of philosophy philosophical? Daunou’s answer is: “history is philosophy, when it consists in a methodical series of facts that are carefully verified and presented as experimental instructions”. In fact, “only the experimental school provides the true method in the historical studies”.

Like Degérando before him, Daunou draws on the historical facts to develop a natural history of philosophy: a classification of the various types of philosophical systems which we can use to establish which is the best. To this end, “the classifications must resemble those of naturalists, that is, they must only summarize the facts. Pretending that they are given and established a priori by the nature of things is a Platonic illusion, that has introduced many prejudices and errors into the sciences”.

In 1829, Daunou could chose between plenty of alternative classifications: for instance, the old division of philosophers into sects to be found in Brucker’s manual, praised by Daunou; the empiricism/rationalism distinction used by the Kantians and by Degérando; and Cousin’s fourfold distinction between idealism, sensualism, scepticism and mysticism. Rejecting all of these classifications, Daunou follows Diderot, Condillac and Condorcet in relying on the good old division between experimental and speculative (or in his terms, contemplative) systems. On the one hand, we have the experimental approach of Aristotle, Bacon, Gassendi, Locke, and Condillac. On the other hand, we have the Platonic attempt to develop philosophical systems a priori. Kant, far from synthesizing these two trends as his disciples claimed, was responsible for perpetuating the Platonic, contemplative illusion. He “delayed the progress of science” and he induced French thinkers to accept the mistaken principle that “the abstract precedes the concrete, sheds light on it and dominates upon it”.

Given Daunou’s assumptions, it is easy to guess what moral he draws from his history of philosophy: we must abandon the Platonic “picture of an idea or imaginary world” and acknowledge that “we owe all progress of physical and moral sciences” to experimental philosophers.

What is surprising, or at least interesting, is that we find these claims in a text published as late as in 1849. Was Daunou a historian attardé, a living fossil in his own time, as Gregorio Piaia states in his very informative survey of Daunou’s work (to which this post owes much) in the Storia delle storie generali della filosofia? It is hard to deny that he was, at least to some extent. However, Daunou’s speculative-experimental distinction was paralleled in Saint-Simon’s contrast between Plato’s and Descartes’ vague speculations on the one hand, Aristotle’s and Bacon’s positive philosophy on the other. The term used by Saint-Simon is “positive”, not “experimental”. However, Saint-Simon’s positive philosophy was based on the experimental method. And in the first volume of Comte’s Course of Positive Philosophy we find the same contrast between the metaphysical spirit, to be rejected, and the positive spirit of those that Daunou regarded as experimental philosophers.

Let’s go back to our initial question on the fate of experimental philosophy in the nineteenth century. Daunou’s work, together with Saint-Simon’s and Comte’s statements, suggests that the notion of experimental philosophy was not simply abandoned in nineteenth century France. Instead, it morphed into the new notion of positive philosophy, or at least it contributed to the definition of this new important movement in the French philosophical scene. I am no expert in nineteenth century French philosophy though. I would love to hear if you find this suggestion plausible.

Degérando’s Experimental History of Philosophy

Alberto Vanzo writes...

So far, on this blog, we have focused on a philosophical movement and a historiographical tradition. Of course, the movement was experimental philosophy. The historiographical tradition was based on the dichotomy of empiricism and rationalism and was first developed by Kantian and post-Kantian authors, like Reinhold and Tennemann, who did not belong to the movement of experimental philosophy. This post is on a historian who was an adherent of experimental philosophy and who endeavoured to employ its methodology in his history of philosophy. He is Joseph-Marie Degérando, who published a Comparative History of the Philosophical Systems, relatively to the Principles of Human Knowledge in 1804. Interestingly, this text is also influenced by the new post-Kantian historiography based on the rationalism-empiricism distinction.

Degérando intends to apply the method of natural history to the history of philosophy. Natural histories were large structured collections of facts about natural phenomena and they were to form the basis for the identification of theories and principles. Degérando’s history of philosophy is a structured collection of facts about past philosophies which will help us identify which philosophical outlook is the best.

Before starting to collect the facts, we must determine the organizing principles of the collection. Philosophers should

    imitate naturalists, who, before entering into the vast regions of natural history, give us regular and simple nomenclatures and they seek the principle of these nomenclatures in the essential characters of each production.

The “nomenclatures” that form the basis for Degérando’s natural history of past philosophers are three dichotomies: scepticism vs dogmatism, empiricism (or sensualism) vs rational (or speculative or contemplative) philosophy; and materialism vs idealism.

Armed with these nomenclatures, historians of philosophy should free themselves of all prejudices and collect historical facts in an unbiased way. Only after having completed this task should historians start philosophizing. Degérando claims to have ascertained “facts as if” he were “foreign to every opinion” and he has “later established an opinion on the basis of the sole testimony of facts”.

In doing this, Degérando does not aim to write a “simple narrative history, to use Bacon’s expression”, but an “inductive or comparative history that converts the facts into “experiences in the path of human spirit.”

    […] the work that we set out to do can be considered as the essay of a treatise of philosophy, […] a treatise conceived of according to the most cautious, albeit most neglected method, the method of experiences. Hence, we dare to offer this essay as an essay of experimental philosophy.

Degérando is strongly influenced by the post-Kantian historiography of Tennemann and other German historians. Like Tennemann, he focuses on epistemological issues concerning “the certainty of human cognitions”, “their origin” and their reality. Degérando uses the distinction between empiricism and rationalism. Like the Kantians, he criticizes them as two unilateral points of view that should be overcome by a higher philosophical standpoint. This is a form of experimental philosophy that is inspired by Bacon and Condillac and is superior to empiricism which as criticized by German historians. Empiricism stops at the facts. The philosophy of experience “transforms them” and identifies general laws.

    Empiricism does not see anything else than the exterior of the temple of nature; experience enters into its sanctuary. Empiricism is an instinct; experience is an art. Empiricism does not see anything else than phenomena, experience ascends from effects to causes. Empiricism is confined to the present; experience learns the future from the past. Empiricism obeys blindly, experience interrogates with method. Everything is mobile, fugitive for empiricism; experience discovers regular and constant combinations underneath the variable appearances. But what need is there to insist on this distinction? He who opens [a book by] Bacon will see it standing out in every page.

The philosophical upshot of Degérando’s experimental history of philosophy

    is spelled out by Bacon’s words, when he said in his preface to the Advancement of Learning: in this way we believe that we are combining, in a manner that is as stable as legitimate, the empirical and rational methods […]

According to Degérando, experimental philosophy, and not Kant’s Critical philosophy is the true, higher synthesis of empiricism and rationalism.

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.