The question of pre-eminence between the Ancients and Moderns is reducible to another. Were trees in ancient times greater than to-day? If they were, then Homer, Plato, and Demosthenes cannot be equalled in modern times; if they were not, they can.
Fontenelle states the problem in this succinct way at the beginning of the Digression. The permanence of the forces of Nature had been asserted by Saint Sorlin and Perrault; they had offered no proof, and had used the principle rather incidentally and by way of illustration. But the whole inquiry hinged on it. If it can be shown that man has not degenerated, the cause of the Moderns is practically won. The issue of the controversy must be decided not by rhetoric but by physics. And Fontenelle offers what he regards as a formal Cartesian proof of the permanence of natural forces.
If the Ancients had better intellects than ours, the brains of that age must have been better arranged, formed of firmer or more delicate fibres, fuller of "animal spirits." But if such a difference existed, Nature must have been more vigorous; and in that case the trees must have profited by that superior vigour and have been larger and finer. The truth is that Nature has in her hands a certain paste which is always the same, which she is ever turning over and over again in a thousand ways, and of which she forms men, animals, and plants. She has not formed Homer, Demosthenes, and Plato of a finer or better kneaded clay than our poets, orators, and philosophers. Do not object that minds are not material. They are connected by a material bond with the brain, and it is the quality of this material bond that determines intellectual differences.
But although natural processes do not change from age to age, they differ in their effects in different climates. "It is certain that as a result of the reciprocal dependence which exists between all parts of the material world, differences of climate, which so clearly affect the life of plants, must also produce some effect on human brains." May it not be said then that, in consequence of climatic conditions, ancient Greece and Rome produced men of mental qualities different from those which could be produced in France? Oranges grow easily in Italy; it is more difficult to cultivate them in France. Fontenelle replies that art and cultivation exert a much greater influence on human brains than on the soil; ideas can be transported more easily from one country to another than plants; and as a consequence of commerce and mutual influence, peoples do not retain the original mental peculiarities due to climate. This may not be true of the extreme climates in the torrid and glacial zones, but in the temperate zone we may discount entirely climatic influence. The climates of Greece and Italy and that of France are too similar to cause any sensible difference between the Greeks or Latins and the French.
Saint Sorlin and Perrault had argued directly from the permanence of vigour in lions or trees to the permanence of vigour in man. If trees are the same as ever, brains must also be the same. But what about the minor premiss? Who knows that trees are precisely the same? It is an indemonstrable assumption that oaks and beeches in the days of Socrates and Cicero were not slightly better trees than the oaks and beeches of to-day. Fontenelle saw the weakness of this reasoning. He saw that it was necessary to prove that the trees, no less than human brains, have not degenerated. But his a priori proof is simply a statement of the Cartesian principle of the stability of natural processes, which he put in a thoroughly unscientific form. The stability of the laws of nature is a necessary hypothesis, without which science would be impossible. But here it was put to an illegitimate use. For it means that, given precisely the same conditions, the same physical phenomena will occur. Fontenelle therefore was bound to show that conditions had not altered in such a way as to cause changes in the quality of nature's organic productions. He did not do this. He did not take into consideration, for instance, that climatic conditions may vary from age to age as well as from country to country.
4.
Having established the natural equality of the Ancients and Moderns, Fontenelle inferred that whatever differences exist are due to external conditions—(1) time; (2) political institutions and the estate of affairs in general.
The ancients were prior in time to us, therefore they were the authors of the first inventions. For that, they cannot be regarded as our superiors. If we had been in their place we should have been the inventors, like them; if they were in ours, they would add to those inventions, like us. There is no great mystery in that. We must impute equal merit to the early thinkers who showed the way and to the later thinkers who pursued it. If the ancient attempts to explain the universe have been recently replaced by the discovery of a simple system (the Cartesian), we must consider that the truth could only be reached by the elimination of false routes, and in this way the numbers of the Pythagoreans, the ideas of Plato, the qualities of Aristotle, all served indirectly to advance knowledge. "We are under an obligation to the ancients for having exhausted almost all the false theories that could be formed." Enlightened both by their true views and by their errors, it is not surprising that we should surpass them.
But all this applies only to scientific studies, like mathematics, physics, and medicine, which depend partly on correct reasoning and partly on experience. Methods of reasoning improve slowly, and the most important advance which has been made in the present age is the method inaugurated by Descartes. Before him reasoning was loose; he introduced a more rigid and precise standard, and its influence is not only manifest in our best works on physics and philosophy, but is even discernible in books on ethics and religion.
We must expect posterity to excel us as we excel the Ancients, through improvement of method, which is a science in itself—the most difficult and least studied of all—and through increase of experience. Evidently the process is endless (il est evident que tout cela n'a point de fin), and the latest men of science must be the most competent.