Thoughts on the Interpretation of Nature Analysis

Denis Diderot


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...

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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...

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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...

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Additional Reading

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...

(The entire section is 432 words.)