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.Moreover,if this force were not equally distributed throughout, there wouldalways be some parts of the world that exert greater gravitationalforce than others, which does not occur.Thus the force really existsin all matter and in the smallest particle of matter.Thus, Attraction is the great source of movement in all of nature.Having demonstrated the existence of this force, Newton indeedanticipated that there would be objections to the word itself.In morethan one passage of his book he warned his reader about the idea ofAttraction, urging him not to confuse this idea with the occult forcesdescribed in Antiquity, and to be willing simply to recognize thatthere is in each body a central force that, from one end of the uni-verse to the other, influences, by the immutable laws of mechanics,the closest as well as the most remote bodies.It is astonishing that, after the solemn warnings of this greatphilosopher, M.Saurin and M.de Fontenelle, who also deserve to becalled philosophers, should have accused him point-blank of sup-porting the delusions of the Aristotelians M.Saurin in theMémoires de l Académie of 1709, and M.de Fontenelle in his ownEloge of Mr.Newton.8Almost all the French, scholars and others, have repeated thisrebuke.One hears everywhere, Why did not Newton make use ofthe word impulse, which we understand so clearly, rather than usingthe word Attraction, which we do not understand? Newton could have answered his critics thus: First, you under-stand the word impulse no better than you understand the word Attraction, and if you cannot imagine why a body moves toward thecenter of another body, neither can you understand by what meansone body pushes another. Secondly, I could not accept impulse, for, to do this, I wouldhave had to know for certain that some celestial matter in fact push-es the planets; now, not only do I not recognize such matter, but Ihave proven that it does not exist. Third, I only use the word Attraction to express an effect that Ihave observed in nature, a certain and indisputable effect of anunknown principle, a quality inherent in matter the cause of whichothers more adept than I may perhaps discover. What then have you taught us? they insist once again, and whyso many calculations to tell us about something that you yourself donot understand? 15_Voltaire_Letter15 1/10/07 12:49 PM Page 57Fifteenth Letter, On the System of Attraction 57 I have taught you, Newton might continue, that the mechan-ics of this central force gives weight to objects in proportion to theirmass, that this central force alone moves the planets and the cometsin their evident relations.I have demonstrated that there cannot beany other cause of weight and movement in celestial bodies; for,since heavy bodies fall to earth according to the obvious effects of thecentral force and the planets continue in their orbits according to thesame effects, if there were yet another force that works on all thesebodies, it would increase their speed or change their direction.Now,not one of these bodies has a single degree of movement, of speed,of direction that cannot be proved to be the effect of this centralforce; thus it is impossible that there be any other. Let me allow Newton to speak for another moment.Would it notbe proper for him to say, I am in a different position from theAncients.They saw, let us say, water raised by pumps and said, Water rises because it has a horror of the void. But I am in the sit-uation of one who was the first to notice that water is raised bypumps, and who leaves it to others to explain the cause of this effect.The anatomist who first said that the arm moves because musclescontract taught men an incontestable truth; would one be lessobliged to him because he did not know why the muscles contract?The cause of air pressure is unknown, but the one who discoveredthis pressure did a great service to physics.The force that I discov-ered is more hidden and more universal; thus I should the more bethanked.I have discovered a new property of matter, one of theCreator s secrets; I have calculated it and demonstrated its effects;should I be tormented because of the name I gave it? One might accuse the vortices of being occult, since no one hasproven their existence.Attraction, on the other hand, is somethingreal, since we have demonstrated its effects and calculated its propor-tions.The cause of this cause lies hidden in God s bosom. Procedeshuc, et non ibis amplius.9 15_Voltaire_Letter15 1/10/07 12:49 PM Page 58 16_Voltaire_Letter16 1/10/07 12:50 PM Page 59Sixteenth LetterOn Mr.Newton s OpticsA new universe was discovered by the philosophers [scientists] ofthe last century, and this new world was all the more difficult tounderstand because no one had suspected that it existed.To the wis-est, it seemed like arrogance even to dare to think that one couldlearn the laws by which the celestial bodies move and how lightbehaves.Galileo by his astronomical discoveries, Kepler by his calcula-tions, Descartes at least in his Dioptrique,1 and Newton in all hisworks, saw the mechanics of the springs that move the world.Geometry reduced the infinite to the calculable.Understanding thecirculation of blood in animals and sap in plants changed nature forus.A new way of existing was imposed on bodies in pneumaticmachines; objects were brought closer to our eyes by means of tele-scopes; finally, after such new discoveries, what Newton learnedabout light rivals anything attained by the most audacious humancuriosity.Until Antonio de Dominis,2 the rainbow seemed an inexplicablemiracle; this philosopher understood that it was a necessary effect ofrain and sun.Descartes made his name immortal by the mathemati-cal explications of this natural phenomenon; he calculated the anglesof reflection of light in drops of rain, and his intelligence seemed topartake of the divine
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