Science / Scientific Culture / Scientific Works

Denis de Casabianca


1The figure of a scientific Montesquieu provides support for the notion of an application of the principles and methods of modern science in the human world. The lively interest that Montesquieu took in the sciences of his time would justify the examination of an epistemological foundation to L’Esprit des lois (Postigliola, p. 480-490). If the figure of the “Newton of the human world” is old, and was relayed and amplified by the reading that the founders of sociology (Comte, Durkheim) did of Montesquieu, we owe to contemporary readings to have renewed it on the basis of an examination of the so-called “youthful” texts devoted to scientific subjects. These tests are principally speeches written in the framework of the activities of the Bordeaux Academy between 1717 and 1725. The table of these writings (Bianchi, p. 109-124; see OC, t. VIII) manifests the variety of the themes addressed. This attraction to the sciences, within a “formative” period, would indicate the frameworks of his philosophy (Barrière, p. 311-327). From such a genetic reading of the work, one concludes that Montesquieu proves to be fascinated by science but, in fact, was a poor scientist (Milhaud, p. 39-41), and the unformulated, paradoxical conclusion that the epistemological basis of the study of law is finally more rigorous than the “scientific” inquiries and experiments to which Montesquieu devoted himself. The author of L’Esprit des lois shows himself to be more “scientific” and modern in his great work and in his principles than in his physical studies that are never examined except as prolegomena to the study of laws. The diversity (not to say the bric-à-brac) of subjects addressed can then be included as the sign of an erudition and an approach that is finally superficial. Montesquieu is perhaps only the figure of an enlightened amateur taken with “the great passion of the century” (Morazé, p. 438), as an educated noble could be in his time. This view is further reinforced by the rhetoric of the academic texts and by the idea that “the sciences overlap and the body of the sciences as a whole is close to literature” (“les sciences se touchent les unes les autres [et que] le corps des sciences tient tout entier aux belles-lettres”, Discours sur les motifs qui doivent nous encourager aux sciences [‘Discourse on the motives that should encourage us into the sciences’], OC, t. VIII, p. 501). Now this “admiration” for natural phenomena, this attention for “variety”, this desire to arouse as much the taste as the intelligence, as at the theatre, are, according to Bachelard, signs of a prescientific mind (La Formation de l’esprit scientifique, p. 29-32). If it is important not to prejudge Montesquieu’s “science”, and to take an interest in what his “scientific culture” might be, that is because, in many ways, his discourse would appear more akin to an esthetics that recalls “cabinets of curiosities” than a genuine scientific mind.

2Yet when we read these “youthful” texts in their own right, it appears that Montesquieu developed a coherent vision of the science of his time and that his “culture” was not that of a simple man of letters entertaining himself. If he only devoted himself to experiments for a time, which can retrospectively be considered as a formative period, we should note that his interest for the sciences (Montesquieu usually uses this term in the plural) was continuous, as is shown in the Essai sur les causes qui peuvent affecter les esprits et les caractères, which is partly repeated in book XIV of L’Esprit des lois, and the brief notations that can be found in the Pensées and the Spicilège. So the affirmation “I used to say: I am neither one of the twenty people in Paris who know those sciences, nor one of the fifty thousand who think they know them” (“Je disais : Je ne suis ni des vingt personnes qui savent ces sciences-là dans Paris, ni des cinquante mille qui croient les savoir”, Pensées, no. 1414) should be taken seriously. If he did not consider himself a scientist, he still did not intend to play at it. He hoped to illuminate the work of researchers; thus we must examine the eye he cast on the efforts of the science of his time in order to identify his notion of scientific “modernity” since Descartes. The speeches present both an overall view of science as “research” and reviews of specific essays presented for the Bordeaux Academy contests. We need to examine the explicit or implicit criteria used by Montesquieu to evaluate them. The Essai d’observations sur l’histoire naturelle read to the Academy on 20 November 1721 has a special status insofar as it is the only text of strictly scientific nature that presents Montesquieu’s own scientific research. If he insists so much on the importance of observations in science, what are his observations like? This point is essential for determining the nature of his “scientific culture”; is it real knowledge that involves the ability to write or to evaluate a physical discourse, or is it a knowledge of vulgarization that enters into the framework of a “scientific culture” common to thinkers of the 18th century?

3The Discours prononcé à la rentrée de l’académie de Bordeaux [‘Discours delivered upon the resumption of the Bordeau Academy’] (1717) and the Discours sur les motifs qui doivent nous encourager aux sciences (1725) present the same overview of the state of the sciences. What does one discover and what can one hope to understand of natural reality? How, from that point, should research be oriented? To answer these questions Montesquieu sketches the setting up of an historical perspective, by situating the discoveries of the 18th century with respect to those of the 17th and comparing modern science and the science of the “Ancients”. The sciences are to be questioned in their evolution, in order to grasp the movement that animates them and must guide the work under way. The sciences are presented as research: they are defined in the very movement which they elaborate and allow the development of. In opposition to fixed knowledge, the dynamics of the sciences is engendered by “observations”, it is paced by “discoveries”. That is why Montesquieu considers the 17th century as “the first age of philosophy” (“le premier âge de la philosophie”, Discours prononcé à la rentrée de l’académie de Bordeaux, 1717, OC, t. VIII, p. 112), and Descartes as the first physicist. The ancient sciences are relegated to a pre-scientific age, not so much because of their errors as because of their incapacity for enabling new discoveries. If a text of the Pensées insists on the importance of the Ancients’ discoveries (Pensées, no. 1424), it is not so that science will be maintained in the frameworks of an outdated knowledge. There is indeed a break in the perspectives of research between Ancients and Moderns, but one must not believe that modern science, which opens a new age for discovery, was the product of spontaneous generation. The point here was to remove an old and possible harmful prejudice: the feeling of facility and superiority can give us an assurance that would make us forget the efforts that must be made in order to conduct any research effectively. The 17th century, which saw the birth of the new natural philosophy, saw the birth of science itself, and the labors of the 18th century exist only in the impetus of this movement which the “great philosophers” have initiated ( Discours prononcé à la rentrée de l’académie de Bordeaux, OC, t. VIII, p. 112): “A third motive that ought to encourage us into the sciences is the well-founded hope of success. What makes the discoveries of this century admirable is that it is not simple truths that have been found, but methods for finding them; it is not a stone for the building, but the instruments and machines to build the whole thing” (“Un troisième motif qui doit nous encourager aux sciences, c’est l’espérance bien fondée d’y réussir. Ce qui rend les découvertes de ce siècle-ci admirables, ce ne sont pas des vérités simples qu’on a trouvées, mais des méthodes pour les trouver ; ce n’est pas une pierre pour l’édifice, mais les instruments et les machines pour le bâtir tout entier.”, Discours sur les motifs qui doivent nous encourager aux sciences, p. 498). The idea of success is not necessarily to be linked with that of completion; it is enough that the scientist be able to search effectively since we have discovered how to discover (trouvé comment trouver).

4Here Montesquieu renews the image of the building, of Cartesian inspiration, but for him the question of the foundation of physics does not refer back to metaphysics. The image of tools shows that the question is not what to build on but how to build. Without considering metaphysical legitimacy, the only purpose is to examine the simple scientific possibility. The hope of success is “well-founded” (ibid.), not because it rests on certain knowledge, but because the research is properly begun. It is the dynamics of research that is founding, and not a static basis. Thus science grounds itself, outside all metaphysics, by the principles and methods it puts into play. The pursuit of research that Descartes initiated also supposes a re-evaluation of his own enterprise and a critique of his physicist theses.

5The state of research is linked to that of the researchers (Discours prononcé à la rentrée de l’académie de Bordeaux, OC, t. VIII, p. 111). But admissions of inability or uncertainty are numerous in the reviews (Discours sur la cause de l’écho, p. 155; Discours sur l’usage des glandes rénales, p. 169; Essai d’observations sur l’histoire naturelle, OC, t. VIII, p. 204-205). In the scientific domain, nothing is set and nothing is definitively fixed; while the limits of human knowledge are endlessly moved, they always still remain to be moved (Discours prononcé à la rentrée de l’académie de Bordeaux, p. 111; Pensées, no. 102): the truth is always receding (Discours sur l’usage des glandes rénales, OC, t. VIII, p. 171). The destructive prejudice for the scientist is to believe the research is almost finished. He must realize that science is not the depository of certain, complete knowledge (Discours sur les motifs qui doivent nous encourager aux sciences, OC, t. VIII, p. 498), but that it is the study that sketches a possible body of knowledge. The scientist lives in the uneasiness of research and “zeal” is the feeling that motivates him to participate in a research which is collective (Discours prononcé à la rentrée de l’académie de Bordeaux, p. 109-110; Discours sur l’usage des glandes rénales, p. 168-169). The true thus remains relative to the state of research and is just a certain degree of probability.

6What is its measure? Montesquieu’s critique or praise in reviews on essays in the Academy contest allows us to identify the criteria used to validate one thesis rather than another (for example: to compare the reviews of the third essay and the one that wins the prize in the Discours sur la cause de la pesanteur des corps, OC, t. VIII, p. 230-233): clarity of argument, internal consistency, ability to produce objections to other explanatory systems and respond to contrary objections, which supposes mastery of the problem and its history, quality and pertinence of observations that can be repeated, measure of the answer given so as not to close the field to future research, participation in a project that reinforces the community of researchers. Montesquieu also insists on the criterion of novelty: “But, Messieurs, what difficulties there are in this research! For after all it is not enough to give us something true, it must be new” (“Mais, messieurs, qu’il y a de difficultés dans cette recherche ! car enfin ce n’est pas assez pour nous de donner une vérité, il faut qu’elle soit nouvelle”, Discours prononcé à la rentrée de l’académie de Bordeaux, p. 111). This last point manifests the provisional character of explanations in science and the dynamics that must animate the research.

7In this movement, it is the observations that guarantee the precision of the argument and are at the base of an empirical process. So the modern scientist is first, for Montesquieu, a good observer. The social standing of the observer or appeal to the authoritative witness do not suffice to validate an observation. One had to make it visible (faire voir; Discours sur l’usage des glandes rénales, p. 167). Observation is in a certain way entirely in the argument that reports it and leads the reader’s eye, revealing a practice that the reader-observer must reproduce; it is in this dialogue and this confrontation of views that the community of observers is constituted. The appeal which Montesquieu makes in Projet d’une histoire de la Terre ancienne et moderne (p. 183-184) testifies to this conscience of the publicity that is essential to the sciences. There is a dissymmetry in the relationship between observation and explanatory hypothesis; the latter must always be submitted to observations, “accept what is concrete” (Paul Hazard, p. 297). While only observations can validate an explanation, the confirmation nevertheless remains provisional, since it is always possible it will be overturned. For a single observation can raise doubt about an explanatory system: “he who is unable to make a system like Newton will make an observation with which he will put the great philosopher to the torture” (“celui qui ne saura pas faire un système comme Newton, fera une observation avec laquelle il mettra à la torture ce grand philosophe”, Essai d’observations sur l’histoire naturelle, p. 223). Observations must always be renewed, first because there is always something still to be discovered, and also because natural reality is constantly changing, finally because observations are the motor of physical inquiry (Discours prononcé à la rentrée de l’académie de Bordeaux, p. 111; Pensées, no. 102; Essai d’observations sur l’histoire naturelle, OC, t. VIII, p. 212). They enable the scientist to advance explanations or, by overturning a hypothesis, in bringing down a system, they oblige the scientist to surpass them, by risking new hypotheses. By confirming or disabling systems, they are the mobile seat of research. “Observations are the history of physics, and systems are its fable” (“Les observations sont l’histoire de la physique, et les systèmes en sont la fable”, Pensées, no. 163).

8It remains to be seen whether these conceptions make Montesquieu an adept of the “experimental method” and how they guide the observations he makes by himself. If there is a taste for experimentation early in the century (Torlais, p. 351), we must remember that at this time experimental procedures remain extremely varied, and the modalities of experiment and the problem of measures are still debated. On these points Montesquieu’s vocabulary is quite floating, using observation and experiment indifferently. So it is appropriate to examine his practice with regard to Newtonian discourse, since that is what was to be imposed as a reference in the long constitution of what was retrospectively to appear as “the” scientific method.

9The reading of Essai d’observations sur l’histoire naturelle is decisive on this point, since we can be sure that Montesquieu is familiar with some theses of the Optics at the time it was written (OC, t. VIII, p. 195). But study of the form of the discourse that relates the observations reveals a non-Newtonian practice of experiment. It is not the point of departure for what Newton calls an analysis, but a means to support or falsify hypotheses. That is moreover the case with the first observation reported insofar as it confirms Newton’s system on colors (Essai d’observations sur l’histoire naturelle, OC, t. VIII, p. 195). The constitutive elements of the discourse of the Optics, control of experimental space, purification of the phenomenon (Licoppe, p. 127-137) are absent from the Essai d’observations. Montesquieu is not seeking to relate a pure phenomenon (reproducible), but he is indeed conscious of reporting “a singular case” (OC, t. VIII, p. 209). Montesquieu’s experimental narrative attempts above all to report what is seen, manifesting the observer’s attention, to “make one see”. The narrative does not attempt to reconstruct the phenomenon; rather it manifests the activity of a view of an object that still escapes him (it is what “we saw”, “perceived”, “discovered”, “noticed”). If recourse to the microscope, the emblematic instrument of modern research, is posited as necessary, we know nothing about the microscope he in fact used in these observations. The microscope is only the prolongation of the eye; it is not yet related to a scientific theory and remains more something that provokes astonishment. Montesquieu attempts to note what appears, but the order of appearance is not always respected: the narrative being concluded by explanation of the phenomenon of the contestation of an adverse thesis, it happens that the elements are mobilized as the demonstration unfolds. The dramatization of the narrative obeys the very idea of research as a movement of discovery. We find throughout the text narrative structures (such as the formula “we did…we saw…”; see Licoppe, p. 53-87; the lexicon is that of the theatre) and forms of argumentation (beginning of a utilitarian proof) that echo the tensions and evolutions of a discourse of experiment in France at the beginning of the 18th century. That is indeed the sign that the Essai d’observations is not merely the text of an enlightened amateur, but that it is worked over by a practice attempting to become stabilized. The distance from Newtonian experiment is also marked by the absence of any mathematical referent in the different discourses. That does not simply come from the fact that Montesquieu had no mathematical training. He manifested some diffidence of geometers, a certain “spirit of system” entailing illusory assurance.

10If these reservations, echoing those of Father Castel (for example, Spicilège, no. 565), can be understood as the mark of a prescientific mind (Bachelard, p. 226-228), they can also prefigure the re-examination of the mathematical model that was to lead to the naturalist enterprise towards the middle of the century. Attention to observations inclines toward natural history.


Gaston Bachelard, La Formation de l’esprit scientifique (1938), Paris: Vrin, 1993.

Pierre Barrière, Un grand provincial: Charles-Louis de Secondat baron de La Brède et de Montesquieu, Bordeaux: Delmas, 1946.

Jean Torlais, “Montesquieu homme de sciences”, Actes du congrès Montesquieu, Bordeaux, 1956, p. 349-353.

Charles Morazé, “Le siècle de la curiosité”, La Science moderne de 1450 à 1800, René Taton ed., Paris: PUF, 1958, p. 435-445.

Gérard Milhaud, “Le regard scientifique de Montesquieu”, Europe 574 (1977), p. 31-41.

Alberto Postigliola, “Dal monde alla nature: gli scritti scientifici di Montesquieu e la genesi epistemologica dell’Esprit des lois”, Oxford : Voltaire Foundation, SVEC 190 (1980), p. 480-490.

Christian Licoppe, La Formation de la pratique scientifique: le discours de l’expérience en France et en Angleterre (1630-1820), Paris: La Découverte, 1996.

Lorenzo Bianchi, “Montesquieu naturaliste”, Montesquieu: les années de formation (1689-1720), Catherine Volpilhac-Auger ed., Cahiers Montesquieu 5, 1999, p. 109-124.

Denis de Casabianca, Montesquieu. De l’étude des sciences à l’esprit des lois, Paris: Champion, 2008.