Thoughts on the Interpretation of Nature by Denis Diderot

First published:Pensées sur l’interprétation de la nature, 1754 (partial translation, 1927)

Type of Philosophy: Epistemology, philosophy of science

Context

A small book consisting of fifty-eight numbered paragraphs, Diderot’s Thoughts on the Interpreta/Iyion of Nature was composed with a view to arousing young people’s interest in scientific experimentation. It did not propose to instruct them but to excite them. “A more capable one than I will acquaint you with the forces of nature: it is sufficient if I have made you employ your own,” he wrote in his dedicatory epistle, “To Young Men Who Are Disposed to Study Natural Philosophy.”

That an essay of this sort was called for in France as late as the middle of the eighteenth century was not entirely because of religious censorship. Quite as much as Scholastic metaphysics, the rationalistic temper of Cartesian science had prejudiced French thinkers against the experimental methods that had been in vogue for a century in England. Voltaire’s Letters Concerning the English Nation (1733), written after two years spent in exile in that country, had endeavored to acquaint the French people with such thinkers as John Locke and Isaac Newton. Diderot’s Thoughts on the Interpretation of Nature, although not expressly mentioning the British authors, had a similar intention.

At a time when ability to read English was rare among the French, Diderot mastered the language and employed himself in translating English works for publication. The present work is clearly an echo of the work of philosopher Francis Bacon, whose Novum Organum (1620; English translation, 1802) also dealt with the interpretation of nature.

A New Approach to Nature

Diderot was convinced that the rationalistic approach to nature, which supposed that there is an exact correspondence between the processes of logic and the laws of the universe, held little promise. The followers of French philosopher René Descartes were accustomed to regarding geometry as the only true science because of the certitude of its results. They left to experimenters only the task of deciding that mathematical expressions happened in fact to fit the order of nature. In Diderot’s opinion, this plan reversed the true procedure. Insofar as it merely elaborates the connection between ideas, mathematics is, he said, merely a branch of metaphysics. It is a kind of game that does nothing to increase understanding of the world. He acknowledged that mathematics had been put to good use by astronomers, but he believed that there was little more to be hoped for in that direction. He predicted that mathematics had reached its zenith and that a hundred years hence there would not be three great geometers in the whole of Europe.

On the other hand, Diderot found no promise in the methods employed by “naturalists” such as Carolus Linnaeus, whose system of classification he ridiculed because it placed humans in the class of quadrupeds and (admittedly) lacked means of distinguishing them from apes. He called such investigators “methodists,” on the ground that they revised the world to fit their method, instead of revising their method to fit the world.

The proper method for studying nature, according to Diderot, was to proceed from facts by way of inference to further facts. Thoughts, he said, are significant only insofar as they are connected with external existence, either by an unbroken chain of experiments, or by an unbroken chain of inferences that starts from observation, or by a series of inferences interspersed with experiments “like weights along a thread hung by its two ends.” He favored the latter. “Without these weights, the thread will be the plaything of the least breath of air.”

Diderot distinguished three stages of experimental reasoning. First is the observation of nature, by which one becomes acquainted with the facts; second is reflection, by which the facts are combined in the mind; third is experiment, by which the combination is tested with reference to further facts. In a simile reminiscent of Bacon, he said that the scientist is like a bee: he must constantly pass back and forth from reflection to the senses. The bee would wear out its wings to no purpose if it failed to return to the hive with its burden, but it would accumulate only useless piles of wax if it were not instructed how to fashion its harvest into honeycomb.

In contrast to the facile optimism with which many enthusiasts for science have written about method, Diderot recognized that the path of the experimenter is straight and narrow and that there are few who find it. The mysterious combination of gifts that makes up “creative genius” intrigued him. People who combine the insight necessary for fruitful observation with powers of reflection and with the skill and patience required for fruitful experiment are exceedingly rare, he said; and he saw nothing that could be done about it. Like a maladroit politician who finds it impossible to take hold of a situation, the average person can spend an entire life observing, say, insects, whereas another takes a passing glance and discovers a whole new order of life.

It was the hope of Diderot that experimenters could learn a lesson from skilled craftspeople, who, without any formal teaching but purely as a result of long experience in handling materials, are able to “smell out” the course of nature and adapt their methods to its ways. As the son of a master cutler, Diderot retained throughout his life a high regard for technical skills, as numerous articles and engravings in the famous Encyclopédie (1751-1772; partial translation, Selected Essays from the Encyclopedy, 1772; complete translation, Encyclopedia, 1965), which he edited, attest. The workers themselves, he said, believe that they divine the ways of nature through a kind of “familiar spirit.” However, he explained their gift as no more than the faculty of perceiving analogies between the qualities of objects that have certain things in common and a massive knowledge of the ways things affect one another when brought into combination. With this insight into the workings of the craftsperson’s mind, the experimenter should be able not merely to equal but to surpass the person in ability.

Diderot would have some sympathy with the person who said that genius is 99 percent perspiration and only 1 percent inspiration, and he recognized that discoveries are often happy accidents, in which error and folly have a share. To make his point, he adapted the story of the man who on his deathbed told his lazy sons that there was treasure buried in the orchard. They spent the summer digging it over. Though they failed to find the object of their greed, they did receive an unusually good crop of fruit. So, said Diderot, experimentation commonly fails to unlock the secrets of the universe in the way people expect, although it yields a reward in pragmatic truth.

Diderot continued the parable. The next year one of the boys told his brothers that in the course of digging over the orchard he had noticed a peculiar depression in one corner. With his mind still on treasure, he convinced them that because the prize did not lie near the surface, it must have been hidden in the bowels of the earth. In this way, he persuaded them to join him in the strenuous task of sinking a deep shaft. After many days, they were at the point of abandoning the project when they came upon not the treasure that they had hoped for but an ancient mine, which they began to work with profit. “Such,” concluded Diderot, “is sometimes the outcome of experiments suggested by a combination of observation with rationalist theories. In this way chemists and geometers, while trying to solve problems which are probably unsolvable, arrive at discoveries more important than the solutions which they sought.”

Interpreting Nature

The strength and originality of Diderot’s book has sometimes been said to lie in the philosopher’s peculiar ability to “smell out” directions that were far beyond the intellectual horizon of the typical eighteenth century philosopher. This gift appears not only in his insights into experimental method but also in his own “interpretation of nature,” for Diderot was not a positivist and had no intention of limiting human knowledge to the results of observation and experimentation.

One of the main differences between the observer of nature and the interpreter of nature is that the latter takes as his point of departure the place where the former leaves off. He conjectures from that which is known that which is yet to be known. He draws from the order of things conclusions abstract and general which have for him all the evidence of sensible and particular truths. And he arrives at the very essence of the world’s order.

Thoughts on the Interpretation of Nature includes several paragraphs devoted to Diderot’s own “conjectures” as to the direction that science should take—suggestions such as “that magnetism and electricity depend upon the same causes.” It also includes an ironical analysis of the philosophy of Pierre-Louis Moreau de Maupertuis, whose Système de la nature (1751; system of nature) had recently appeared. Diderot agreed, on the whole, with Maupertuis’s position, and he assumed a critical air in order to develop further implications of the theory while professing to be scandalized at the outcome. Diderot had already spent three months in prison for advanced thinking and had learned to envelop his speculations in studied ambiguity.

Perhaps the “thought” that governs all the rest of Diderot’s “interpretations of nature” is that when people discover that every event must have a cause, they have reached the frontier of metaphysical knowledge. There is no point in speculating about any higher cause, nor in asking “why” things are constituted the way they are. At an earlier stage of his development, Diderot had embraced the deistic account of origins that he found in the third earl of Shaftesbury’s Characteristicks of Men, Manners, Opinions, Times (1711). In the present work, he took his stand on the side of what today would be called naturalism, which at that time was called Spinozism.

Elements and Evolution

It seemed to Diderot that the possibility of experimental science rested on the assumption that there is only one causal principle operative in the world. However, he was so much impressed by the variety that nature exhibits at every level that he shied away from the view that the world is made of a uniform substance. Instead, he favored the materialistic version of Gottfried Wilhelm Leibniz’s philosophy suggested in Maupertuis’s book. In this view, every “element” that goes to make up nature is essentially different from every other. Each element is divisible into molecules, themselves incapable of further division. Moreover, the molecules must be thought of as “organic,” endowed with the rudiments of desire and aversion, of feeling and thought. Only thus could one account for the whole range of nature.

In his oblique fashion, Diderot gave thanks for the biblical account of Creation. If people had been left to their own speculations, he said, the best they could do would be to infer that the elements of living beings had been mingled with other elements from all eternity in the total mass, and that they have joined together to form beasts and people “merely because it was possible for it to happen!” He allowed himself to speculate that a species of animals might come into being, reach maturity, and perish—just as happens in the case of individual members of a species. Giving full rein to his imagination, he suggested that living beings must have passed through infinite stages of development, acquiring in turn “movement, sensation, imagination, thought, reflection, consciousness, sentiments, passions, signs, gestures, sounds, articulate sounds, speech, laws, sciences, and arts,” with millions of years between each of these acquisitions—that perhaps still other developments are yet to come, of which we are ignorant; that the process may come to a standstill; and that eventually the product of these transformations may disappear from nature forever. “Religion,” he said, “spares us all these wanderings and the mental labor which it would require to follow them out.”

Diderot’s interest in biological evolution was not merely of this speculative sort. Familiar with comparative anatomy, he observed that every one of the quadrupeds is patterned on the same “prototype,” that nature merely lengthens, shortens, modifies, or multiplies the same organs. “Imagine the fingers of a hand bound together and the material of the nails increased to envelop the whole: in place of a man’s hand you would have a horse’s hoof.” Such considerations led him to conclude that there is no real division between the animal kingdoms. Nature, he said, is like a woman who loves to vary her costume. She does not require many different outfits because she knows how, by varying a sleeve or a collar, adding a pleat or letting down a hem, to achieve an infinite number of effects while using the same pattern.

Humanity and Nature

Diderot’s greatest boldness, however, lay in the view that he took of humanity’s role in nature and of the role of science in human affairs. The Copernican revolution had convinced enlightened thinkers that the earth is not the center of the universe, but the majority of them continued to think of humans as occupying a favored position. In rejecting deism and turning back to the more expansive tradition of philosophers Giordano Bruno and Baruch Spinoza, Diderot sharply challenged the optimism of his day, particularly as it pertained to the advancement of learning.

In principle, Diderot admitted that, just as mathematicians, in examining the properties of a curve, find the same properties present under different aspects, so experimental physicists may eventually find a single hypothesis that covers such different properties as weight, elasticity, electricity, and magnetism. However, how many intermediary hypotheses, he exclaimed, had to be found before the gaps could be filled in. Nor could there be any shortcut, such as exists in mathematics, where intermediary propositions can be arrived at by deduction. On the contrary, he saw a deplorable tendency for various branches of science to build mutually exclusive systems of explanation. Classic mechanics was such a system. Diderot said it was a labyrinth in which people must wander without hopes of ever reaching understanding with other sciences.

Diderot expressed most vividly the disparity between our fragmentary knowledge and the vastness and variety of nature. “When one begins to compare the infinite multitude of the phenomena of nature with the limits of our understanding and the weakness of our faculties, can one be surprised that our work lags and frequently drags to a halt, and that all which we possess is a few broken and isolated links of the great chain of being?” Suppose that experimental philosophy should continue for several centuries. Where is the mind that could take it all in? How many volumes would be required to record it? How far would any one person be able to read? Are people not, he asked, “as foolish as the men of Babel? We know the infinite distance that separates earth from heaven, yet we do not cease to build the tower.” A confusion of tongues is bound to result that will lead to an abandoning of the effort.

This pessimism was directed against barren intellectualism, the attempt to understand the world in abstract terms, and finds its counterpart in Voltaire’s Candide: Ou, L’Optimisme (1759; Candide: Or, All for the Best, 1759), where wisdom is said to consist in cultivating one’s garden instead of speculating about matters too high for one. Diderot complained that people are content to live in hovels while raising uninhabitable palaces that reach to the clouds. It was his hope that experimental science would alter that condition and would bring into being vast stores of knowledge that would alleviate the human condition. However, he predicted that when this change had come about, people would lose interest in science just as they had (in his opinion) already lost interest in geometry:

Utility circumscribes everything. It is utility that, in a few centuries, will set the limits to experimental physics as it is on the point of doing to geometry. I accord several centuries to this study because the sphere of its utility is infinitely more extensive than that of any abstract science, and because it is undeniably the basis of all true knowledge.

Principal Ideas Advanced

•The rationalistic approach to nature is useless; to study nature, one must proceed from facts by the use of methods of inference.

•Inferences should be checked by experiments; reflection and observation should supplement each other in empirical inquiry.

•By acts of interpretation, one succeeds in becoming more than a mere observer of nature; by drawing general conclusions from the order of things, one arrives at an understanding of the world’s order.

•There is one causal principle operative in the world, but there are numerous elements, divisible into molecules that are themselves indivisible.

•Experimental physics is the basis of all true knowledge.

Bibliography

Blum, Carol. Diderot: The Virtue of a Philosopher. New York: Viking Press, 1974. Focuses on Denis Diderot’s concern for the moral life and his intellectual quest to define what such an existence involves. A well-written study that draws on biography, letters, and published writings.

Bremner, Geoffrey. Order and Chance: The Pattern of Diderot’s Thought. Cambridge, England: Cambridge University Press, 1983. Bremner seeks a pattern in Diderot’s thought and concludes that, in his best works, order and chance are complementary concepts. Interesting insights, suitable for advanced undergraduates.

Brewer, Daniel. The Discourse of Enlightenment in Eighteenth-Century France: Diderot and the Art of Philosophizing. Cambridge Studies in French, No. 42. Cambridge, England: Cambridge University Press, 1993. This somewhat difficult study examines the interplay between critical knowledge and its representation. Examining Diderot’s work in philosophy, science, the fine arts, and literature, Brewer points to its remarkable similarity to aspects of modern critical theory.

Crocker, Lester G. Diderot’s Chaotic Order: Approach to Synthesis. Princeton, N.J.: Princeton University Press, 1974. Sets forth the view that Diderot dealt with order and disorder as categories of experience and modes of thought. Argues that, for Diderot, the tension between these two opposites constitutes a universal process. For advanced undergraduates.

Fellows, Otis. Diderot. Boston: Twayne, 1977. This chronological overview touches briefly on almost all of Diderot’s works. It stresses Diderot’s modernity, traces the evolution of his thought, and imparts some of the excitement of his writing. Contains a helpful annotated bibliography.

France, Peter. Diderot. New York: Oxford University Press, 1983. A good, short introduction concentrating on Diderot’s ideas. Arranged topically, it covers Diderot’s political, social, and aesthetic views, and includes a useful annotated bibliography.

Rex, Walter E. Diderot’s Counterpoints: The Dynamics of Contrariety in His Major Works. Oxford: Voltaire Foundation, 1998. This books offers some history and criticism of Diderot’s work.

Simon, Julia. Mass Enlightenment: Critical Studies in Rousseau and Diderot. Albany: State University of New York Press, 1995. An examination of the social and political thought in the work of Rousseau and Diderot.

Umdank, Jack, and Herbert Joseph, eds. Diderot: Digression and Dispersion, a Bicentennial Tribute. Lexington, Ky.: French Forum, 1984. Presents nineteen essays that cover Diderot’s many activities and interests. In their diversity, the contributions mirror the editors’ view that Diderot did not seek unity but rather regarded diversity as the rule of nature.

Wilson, Arthur M. Diderot. New York: Oxford University Press, 1972. The definitive biography. Places Diderot within the context of the Enlightenment and considers the development of his ideas on such matters as religion, emotion and reason, order and diversity, determinism and chance.