Diderot and the Encyclopædists (Vol. 2 of 2)

by John Morley

I.

Decidedly the most important of the pieces of which we have not yet spoken must be counted the Thoughts on the Interpretation of Nature (1754). His study of Bacon and the composition of the introductory prospectus of the Encyclopædia had naturally filled Diderot’s mind with ideas about the universe as a whole. The great problem of man’s knowledge of this universe,—the limits, the instruments, the meaning of such knowledge, came before him with a force that he could not evade. Maupertuis had in 1751, under the assumed name of Baumann, an imaginary doctor of Erlangen, published a dissertation on the Universal System of Nature, in which he seems to have maintained that the mechanism of the universe is one and the same throughout, modifying itself, or being modified by some vital element within, in an infinity of diverse ways.[207] Leibnitz’s famous idea, of making nature invariably work with the minimum of action, was seized by Maupertuis, expressed as the Law of Thrift, and made the starting-point of speculations that led directly to Holbach and the System of Nature.[208] The Loi d’Epargne evidently tended to make unity of all the forces of the universe the keynote or the goal of philosophical inquiry. At this time of his life, Diderot resisted Maupertuis’s theory of the unity of vital force in the universe, or perhaps we should rather say that he saw how open it was to criticism. His resistance has none of his usual air of vehement conviction. However that may be, the theory excited his interest, and fitted in with the train of meditation which his thoughts about the Encyclopædia had already set in motion, and of which the Pensées Philosophiques of 1746 were the cruder prelude.

The Thoughts on the Interpretation of Nature are, in form as in title, imitated from those famous Aphorismi de Interpretatione Naturæ et Regni Hominis, which are more shortly known to all men as Bacon’s Novum Organum.[209] The connection between the aphorisms is very loosely held. Diderot began by premising that he would let his thoughts follow one another under his pen, in the order in which the subjects came up in his mind; and he kept his word. Their general scope, so far as it is capable of condensed expression, may be described as a reconciliation between the two great classes into which Diderot found thinkers upon Nature to be divided; those who have many instruments and few ideas, and those who have few instruments and many ideas,—in other words, between men of science without philosophy, and philosophers without knowledge of experimental science.

In the region of science itself, again, Diderot foresees as great a change as in the relations between science and philosophy. “We touch the moment of a great revolution in the sciences. From the strong inclination of men’s minds towards morals, literature, the history of nature and experimental physics, I would almost venture to assert that before the next hundred years are over, there will not be three great geometers to be counted in Europe. This science will stop short where the Bernouillis, the Eulers, the Maupertuis, the Clairauts, the Fontaines, the D’Alemberts, the Lagranges have left it. They will have fixed the Pillars of Hercules. People will go no further.” Those who have read Comte’s angry denunciations of the perversions of geometry by means of algebra, and of the waste of intellectual force in modern analysis,[210] will at least understand how such a view as Diderot’s was possible. And no one will be likely to deny that, whether or not the pillars of the geometrical Hercules were finally set a hundred years ago, the great discoveries of the hundred years since Diderot have been, as he predicted, in the higher sciences. The great misfortune of France was that the supremacy of geometry coincided with the opening of the great era of political discussion. The definitions of Montesquieu’s famous book, which opened the political movement in literature, have been shown to be less those of a jurisconsult than of a geometer.[211] Social truths, with all their profound complexity, were handled like propositions in Euclid, and logical deductions from arbitrary premises were treated as accurate representations of real circumstance. The repulse of geometry to its proper rank came too late.

Comte always liberally recognised Diderot’s genius, and any reader of Comte’s views on the necessities of subjective synthesis will discern the germ of that doctrine in the following remarkable section:

“When we compare the infinite multitude of the phenomena of nature with the limits of our understandings and the weakness of our organs, can we ever expect anything else from the slowness of our work, from the long and frequent interruptions, and from the rarity of creative genius than a few broken and separated pieces of the great chain that binds all things together? Experimental philosophy might work for centuries of centuries, and the materials that it had heaped up, finally reaching in their number beyond all combination, would still be far removed from an exact enumeration. How many volumes would it not need to contain the mere terms by which we should designate the distinct collections of phenomena, if the phenomena were known? When will the philosophic language be complete? If it were complete, who among men would be able to know it? If the Eternal, to manifest his power still more plainly than by the marvels of nature, had deigned to develop the universal mechanism on pages traced by his own hand, do you suppose that this great book would be more comprehensible to us than the universe itself? How many pages of it all would have been intelligible to the philosopher who, with all the force of head that had been conferred upon him, was not sure of having grasped all the conclusions by which an old geometer determined the relation of the sphere to the cylinder? We should have in such pages a fairly good measure of the reach of men’s minds, and a still more pungent satire on our vanity. We should say, Fermat went to such a page, Archimedes went a few pages further.

“What then is our end? The execution of a work that can never be achieved, and which would be far beyond human intelligence if it were achieved. Are we not more insensate than the first inhabitants of the plain of Shinar? We know the immeasurable distance between the earth and the heavens, and still we insist on rearing our tower.

“But can we presume that there will not come a time when our pride will abandon the work in discouragement? What appearance is there that, narrowly lodged and ill at its ease here below, our pride should obstinately persist in constructing an uninhabitable palace beyond the earth’s atmosphere? Even if it should so insist, would it not be arrested by the confusion of tongues, which is already only too perceptible and too inconvenient in natural history? Besides, it is utility that circumscribes all. It will be utility that in a few centuries will set bounds to experimental physics, as it is on the eve of setting bounds to geometry. I grant centuries to this study, because the sphere of its utility is infinitely more extensive than that of any abstract science, and it is without contradiction the base of our real knowledge.”[212]

We cannot wonder that when Comte drew up his list of the hundred and fifty volumes that should form the good Positivist’s library in the nineteenth century, he should have placed Diderot’s Interpretation of Nature on one side of Descartes’ Discourse on Method, with Bacon’s Novum Organum on the other.

The same spirit finds even stronger and more distinct expression in a later aphorism:—“Since the reason cannot understand everything, imagination foresee everything, sense observe everything, nor memory retain everything; since great men are born at such remote intervals, and the progress of science is so interrupted by revolution, that whole ages of study are passed in recovering the knowledge of the centuries that are gone,—to observe everything in nature without distinction is to fail in duty to the human race. Men who are beyond the common run in their talents ought to respect themselves and posterity in the employment of their time. What would posterity think of us if we had nothing to transmit to it save a complete insectology, an immense history of microscopic animals? No—to the great geniuses great objects, little objects to the little geniuses” (§ 54).

Diderot, while thus warning inquirers against danger on one side, was alive to the advantages of stubborn and unlimited experiment on the other. “When you have formed in your mind,” he says, “one of those systems which require to be verified by experience, you ought neither to cling to it obstinately nor abandon it lightly. People sometimes think their conjectures false, when they have not taken the proper measures to find them true. Obstinacy, even, has fewer drawbacks than the opposite excess. By multiplying experiments, if you do not find what you want, it may happen that you will come on something better. Never is time employed in interrogating nature entirely lost” (§ 42). The reader will not fail to observe that this maxim is limited by the condition of verifiableness. Of any system that could not be verified by experience Diderot would have disdained to speak in connection with the interpretation of nature.

This, of course, did not prevent him from hypothesis and prophecy which he himself had not the means of justifying. For example, he said that just as in mathematics, by examining all properties of a curve we find that they are one and the same property presented under different faces, so in nature when experimental physics are more advanced, people will recognise that all the phenomena, whether of weight, or elasticity, or magnetism, or electricity, are only different sides of the same affection (§ 44). But he was content to leave it to posterity, and to build no fabric on unproved propositions.

In the same scientific spirit he penetrated the hollowness of every system dealing with Final Causes:

“The physicist, whose profession is to instruct and not to edify, will abandon the Why, and will busy himself only with the How.... How many absurd ideas, false suppositions, chimerical notions in those hymns which some rash defenders of final causes have dared to compose in honour of the Creator? Instead of sharing the transports of admiration of the prophet, and crying out at the sight of the unnumbered stars that light up the midnight sky, The heavens declare the glory of God, and the firmament sheweth his handiwork, they have given themselves up to the superstition of their conjectures. Instead of adoring the All-Powerful in the creation of nature, they have prostrated themselves before the phantoms of their imagination. If any one doubts the justice of my reproach, I invite him to compare Galen’s treatise on the use of parts of the human body, with the physiology of Boerhaave, and the physiology of Boerhaave with that of Haller; I invite posterity to compare the systematic or passing views of Haller with what will be the physiology of future times. Man praises the Eternal for his own poor views; and the Eternal who hears from the elevation of his throne, and who knows his own design, accepts the silly praise and smiles at man’s vanity” (§ 56).

The world has advanced rapidly along this path since Diderot’s day, and has opened out many new and unsuspected meanings by the way. Perhaps the advance has been less satisfactory in working out, in a scientific way, the philosophy that is implied in the following adaptation of the Leibnitzian and Maupertuisian suggestion of the law of economy in natural forces:—“Astonishment often comes from our supposing several marvels, where in truth there is only one; from our imagining in nature as many particular acts as we can count phenomena, whilst nature has perhaps in reality never produced more than one single act. It seem even that, if nature had been under the necessity of producing several acts, the different results of such acts would be isolated; that there would be collections of phenomena independent of one another, and that the general chain of which philosophy assumes the continuity, would break in many places. The absolute independence of a single fact is incompatible with the idea of an All; and without the idea of a Whole, there can be no Philosophy” (§ 11).

At length Diderot concludes by a series of questions which he thinks that philosophers may perhaps count worthy of discussion. What is the difference, for example, between living matter and dead? Does the energy of a living molecule vary by itself, or according to the quantity, the quality, the forms of the dead or living matter with which it is united? We need not continue the enumeration, because Diderot himself suddenly brings them to an end with a truly admirable expression of his sense of how unworthy they are of the attention of serious men, who are able to measure the difference between a wise and beneficent use of intelligence, and a foolish and wasteful misuse of it. “When I turn my eyes,” he says, “to the works of men, and see the cities that are built on every side, all the elements yoked to our service, languages fixed, nations civilised, harbours constructed, lands and skies measured—then the world seems to me very old. When I find man uncertain as to the first principles of medicine and agriculture, as to the properties of the commonest substances, as to knowledge of the maladies that afflict him, as to the pruning of trees, as to the best form for the plough, then it seems as if the earth had only been inhabited yesterday. And if men were wise, they would at last give themselves up to such inquiries as bear on their wellbeing, and would not take the trouble to answer my futile questions for a thousand years at the very soonest; or perhaps, even, considering the very scanty extent that they occupy in space and time, they would never deign to answer them at all.”