Philosophical Dictionary, by Voltaire


M. Duval, who, if I mistake not, was librarian to the Emperor Francis I., gives us an account of the manner in which, in his childhood, pure instinct gave him the first ideas of astronomy. He was contemplating the moon which, as it declined towards the west, seemed to touch the trees of a wood. He doubted not that he should find it behind the trees, and, on running thither, was astonished to see it at the extremity of the horizon.

The following days his curiosity prompted him to watch the course of this luminary, and he was still more surprised to find that it rose and set at various hours. The different forms which it took from week to week, and its total disappearance for some nights, also contributed to fix his attention. All that a child could do was to observe and to admire, and this was doing much; not one in ten thousand has this curiosity and perseverance.

He studied, as he could, for three years, with no other book than the heavens, no other master than his eyes. He observed that the stars did not change their relative positions; but the brilliancy of the planet Venus having caught his attention, it seemed to him to have a particular course, like that of the moon. He watched it every night; it disappeared for a long time; and at length he saw it become the morning instead of the evening star. The course of the sun, which from month to month, rose and set in different parts of the heavens, did not escape him. He marked the solstices with two staves, without knowing what the solstices were.

It appears to me that some profit might be derived from this example, in teaching astronomy to a child of ten or twelve years of age, and with much greater facility than this extraordinary child, of whom I have spoken, taught himself its first elements.

It is a very attractive spectacle for a mind disposed to the contemplation of nature to see that the different phases of the moon are precisely the same as those of a globe round which a lighted candle is moved, showing here a quarter, here the half of its surface, and becoming invisible when an opaque body is interposed between it and the candle. In this manner it was that Galileo explained the true principles of astronomy before the doge and senators of Venice on St. Mark’s tower; he demonstrated everything to the eyes.

Indeed, not only a child, but even a man of mature age, who has seen the constellations only on maps or globes, finds it difficult to recognize them in the heavens. In a little time the child will quite well comprehend the causes of the sun’s apparent course, and the daily revolutions of the fixed stars.

He will, in particular, discover the constellations with the aid of these four Latin lines, made by an astronomer about fifty years ago, and which are not sufficiently known:

Delta Aries, Perseum Taurus, Geminique Capellam;

Nil Cancer, Plaustrum Leo, Virgo Coman, atque Bootem,

Libra Anguem, Anguiferum fert Scorpios; Antinoum Arcus;

Delphinum Caper, Amphora Equos, Cepheida Pisces.

Nothing should be said to him about the systems of Ptolemy and Tycho Brahe, because they are false; they can never be of any other service than to explain some passages in ancient authors, relating to the errors of antiquity. For instance, in the second book of Ovid’s “Metamorphoses,” the sun says to Phaëton:

Adde, quod assidua rapitur vertigine cœlum;

Nitor in adversum; nec me, qui cætera, vincit

Impetus; et rapido contrarius evehor orbi.

A rapid motion carries round the heavens;

But I— and I alone — resist its force,

Marching secure in my opposing path.

This idea of a first mover turning the heavens round in twenty-four hours with an impossible motion, and of the sun, though acted upon by this first motion, yet imperceptibly advancing from west to east by a motion peculiar to itself, and without a cause, would but embarrass a young beginner.

It is sufficient for him to know that, whether the earth revolves on its own axis and round the sun, or the sun completes his revolution in a year, appearances are nearly the same, and that, in astronomy, we are obliged to judge of things by our eyes before we examine them as natural philosophers.

He will soon know the cause of the eclipses of the sun and the moon, and why they do not occur every night. It will at first appear to him that, the moon being every month in opposition to and in conjunction with the sun, we should have an eclipse of the sun and one of the moon every month. But when he finds that these two luminaries are not in the same plane and are seldom in the same line with the earth, he will no longer be surprised.

He will easily be made to understand how it is that eclipses have been foretold, by knowing the exact circle in which the apparent motion of the sun and the real motion of the moon are accomplished. He will be told that observers found by experience and calculation the number of times that these two bodies are precisely in the same line with the earth in the space of nineteen years and a few hours, after which they seem to recommence the same course; so that, making the necessary allowances for the little inequalities that occurred during those nineteen years, the exact day, hour, and minute of an eclipse of the sun or moon were foretold. These first elements are soon acquired by a child of clear conceptions.

Not even the precession of the equinoxes will terrify him. It will be enough to tell him that the sun has constantly appeared to advance in his annual course, one degree in seventy-two years, towards the east; and this is what Ovid meant to express: “Contrarius evehor orbi;” —“Marching secure in my opposing path.”

Thus the Ram, which the sun formerly entered at the beginning of spring, is now in the place where the Bull was then. This change which has taken place in the heavens, and the entrance of the sun into other constellations than those which he formerly occupied, were the strongest arguments against the pretended rules of judicial astrology. It does not, however, appear that this proof was employed before the present century to destroy this universal extravagance which so long infected all mankind, and is still in great vogue in Persia.

A man born, according to the almanac, when the sun was in the sign of the Lion, was necessarily to be courageous; but, unfortunately, he was in reality born under the sign of the Virgin. So that Gauric and Michael Morin should have changed all the rules of their art.

It is indeed odd that all the laws of astrology were contrary to those of astronomy. The wretched charlatans of antiquity and their stupid disciples, who have been so well received and so well paid by all the princes of Europe, talked of nothing but Mars and Venus, stationary and retrograde. Such as had Mars stationary were always to conquer. Venus stationary made all lovers happy. Nothing was worse than to be born under Venus retrograde. But the fact is that these planets have never been either retrograde or stationary, which a very slight knowledge of optics would have sufficed to show.

How, then, can it have been that, in spite of physics and geometry, the ridiculous chimera of astrology is entertained even to this day, so that we have seen men distinguished for their general knowledge, and especially profound in history, who have all their lives been infatuated by so despicable an error? But the error was ancient, and that was enough.

The Egyptians, the Chaldæans, the Jews, foretold the future; therefore, it may be foretold now. Serpents were charmed and spirits were raised in those days; therefore, spirits may be raised and serpents charmed now. It is only necessary to know the precise formula made use of for the purpose. If predictions are at an end, it is the fault, not of the art, but of the artist. Michael Morin and his secret died together. It is thus that the alchemists speak of the philosopher’s stone; if, say they, we do not now find it, it is because we do not yet know precisely how to seek it; but it is certainly in Solomon’s collar-bone. And, with this glorious certainty, more than two hundred families in France and Germany have ruined themselves.

It is not then to be wondered at that the whole world has been duped by astrology. The wretched argument, “there are false prodigies, therefore there are true ones,” is neither that of a philosopher, nor of a man acquainted with the world. “That is false and absurd, therefore it will be believed by the multitude,” is a much truer maxim.

It is still less astonishing that so many men, raised in other things so far above the vulgar; so many princes, so many popes, whom it would have been impossible to mislead in the smallest affair of interest, have been so ridiculously seduced by this astrological nonsense. They were very proud and very ignorant. The stars were for them alone; the rest of the world a rabble, with whom the stars had nothing to do. They were like the prince who trembled at the sight of a comet, and said gravely to those who did not fear it, “You may behold it without concern; you are not princes.”

The famous German leader, Wallenstein, was one of those infatuated by this chimera; he called himself a prince, and consequently thought that the zodiac had been made on purpose for him. He never besieged a town, nor fought a battle, until he had held a council with the heavens; but, as this great man was very ignorant, he placed at the head of this council a rogue of an Italian, named Seni, keeping him a coach and six, and giving him a pension of twenty thousand livres. Seni, however, never foresaw that Wallenstein would be assassinated by order of his most gracious sovereign, and that he himself would return to Italy on foot.

It is quite evident that nothing can be known of the future, otherwise than by conjectures. These conjectures may be so well-founded as to approach certainty. You see a shark swallow a little boy; you may wager ten thousand to one that he will be devoured; but you cannot be absolutely sure of it, after the adventures of Hercules, Jonas, and Orlando Furioso, who each lived so long in a fish’s belly.

It cannot be too often repeated that Albertus Magnus and Cardinal d’Ailli both made the horoscope of Jesus Christ. It would appear that they read in the stars how many devils he would cast out of the bodies of the possessed, and what sort of death he was to die. But it was unfortunate that these learned astrologers foretold all these things so long after they happened.

We shall elsewhere see that in a sect which passes for Christian, it is believed to be impossible for the Supreme Intelligence to see the future otherwise than by supreme conjecture; for, as the future does not exist, it is, say they, a contradiction in terms to talk of seeing at the present time that which is not.

Last updated Tuesday, March 4, 2014 at 18:25