Descartes

by A. C. Grayling

  O Lord my God, thou art very great; thou art clothed with honour and majesty:

  Who coverest thyself with light as with a garment: who stretchest out the heavens like a curtain:

  Who layeth the beams of his chambers in the waters: who maketh the clouds his chariot:

  Who walketh upon the wings of the wind:

  Who maketh his angels spirits; his ministers a flaming fire:

  Who laid the foundation of the earth, that it should not be removed for ever.

  The crucial passage is of course this last, italicised line. For the faithful its import is reinforced by the minatory implications of God's question to Job out of the whirlwind: "Where were you when I laid the foundation of the earth?" On the authority of Psalm 104 the Church announced that Copernicus, Galileo and science had to be wrong. Eighteen years beforehand, in 1616, Cardinal Bellarmine and the Inquisition had censured Galileo for premising that the earth moves. He had not taken heed, and now the Inquisition was trying to suppress the absurdity of the doctrine that the earth swings through space; for not only does divinely inspired scripture tell us the contrary, but so does the evidence of one's own eyes—for, when one looks out of the Vatican windows at the pilgrims on their knees in St. Peter's Square, one sees the world standing still and firm, with the heavens circling quietly and steadily above.

  The prosecution of Galieo did not come out of nowhere. For two decades Galieo's discoveries had been a thorn in doctrinal flesh. This began with his perfection of the telescope and his use of it to make epoch-changing discoveries. In 1609 he received reports of a powerful "spyglass" made by a Dutchman, and set about perfecting one for himself, using his wonderful skills as a craftsman and mathematician and basing his endeavours, as he put it, on the "doctrine of refraction." He made a number of telescopes, using existing techniques to produce instruments with a magnification of about four, but quickly learning how to grind and polish lenses more effectively so that he could attain magnifications of eight or nine. He saw the immense commercial, military and marine potential of what he had done—and for a handsome increase in salary gave the rights for the manufacture of telescopes to the Senate of Venice. But he also saw its scientific value. He had a fine instrument available by the end of 1609, which he called a "perspicillum." He put it to his eye and gazed through it at the heavens—and in the two months of December and January 1609-10 transformed history. He saw the mountains on the moon, he saw that the Milky Way consisted of innumerable individual stars, and he saw the satellites of Jupiter. He promptly named them "the Medicean stars" and along with an announcement of this flattering appellation he sent a good telescope to the Medici prince in question, the Grand Duke of Tuscany, who thereupon appointed him "Ducal Mathematician and Philosopher" at an excellent wage. This was timely; the Venetian Senate had just woken to the fact that their "rights" to the manufacture of telescopes were worthless, since Galileo had not invented the instrument, and anyway Venice could not hope to control the manufacture of telescopes elsewhere in the world. They froze Galileo's salary, but by then he was on his way to Tuscany.

  Galileo published his telescopic discoveries in a little book called Sidereus Nuncius (the Starry Messenger). But in the next couple of years he made more accurate observations of the moons of Jupiter and, 'while puzzling over inconsistencies in his data, realised he had to take into account variables in his own position relative to the motions he was observing—specifically, variables which had to be caused by the motion of the earth round the sun, thus showing that Copernicus' model was not, as Copernicus himself had taken it, merely a convenience for simplifying calculations of the motions of heavenly bodies, but actually correct. Galileo had in fact known this for a long time; in a 1598 letter to Kepler he acknowledged that he was a Copernican. But he did not make an issue of his convictions in this respect, and for the time being kept them private. He was feted in Rome for his telescopic discoveries, and elected to fellowship of the Accademia dei Lincei, which gave him great satisfaction.

  What brought the Copernican question to the fore were the public pronouncements of Galileo's former pupil Castelli, by then professor of mathematics at Pisa. Castelli was asked by the Grand Duke of Tuscany, Cosimo II, and his mother the Grand Duchess Christina of Lorraine, to explain the discrepancy between scripture and the Copernican model. In complying he defended the Copernican model, and wrote to Galileo to show off to his former teacher about how successful he had been in making the Copernican case. In his reply Galileo asserted his view that the Bible should always be interpreted according to what science had discovered, and not vice versa. Copies of this letter were shown by Galileo's enemies to the Inquisition, which, however, at that point did nothing—they were biding their time. Then, in 1616, Galileo wrote directly to the Grand Duchess iterating his conviction that scripture should not be taken literally if it is inconsistent with what mathematically based science reveals about the world. In the process of arguing for this view he made it clear that he took the Copernican theory to be literally true. "I hold that the Sun is located at the centre of the revolutions of the heavenly orbs and does not change place, and that the Earth rotates on itself and moves around it," he wrote. "I confirm this view not only by refuting Ptolemy's and Aristotle's arguments, but also by producing many on the other side, especially some pertaining to physical effects whose causes perhaps cannot be determined in any other way, and other astronomical discoveries; these discoveries clearly confute the Ptolemaic system, and they agree admirably with the Copernican position and confirm it."33

  This was a provocation that the Church could not ignore. Pope Paul V instructed Cardinal Bellarmine to have the Copernican theory examined by the Sacred Congregation of the Index, as the Inquisition was officially known. On 24 February 1616 the Cardinals of the Inquisition took submissions from theological experts and concluded that the Copernican theory must be condemned. Cardinal Bellarmine informed Galileo, who had taken no part in the enquiry, that he was henceforth forbidden to hold Copernican views, and certainly forbidden to teach or promote them.

  The proscription kept Galileo quiet for a time, but when Cardinal Matteo Barberini became Pope as Urban VIII in 1623 he felt less constrained, for Barberini had long been an admirer of his work. Galileo promptly dedicated his new bookjust about to be published, to Urban VIII. This was // Saggiatore (TheAssayer), setting out Galileo's ideas about scientific method, and containing the following celebrated passage: "Philosophy is written in this grand book, the universe, which stands continually open to our gaze. But the book cannot be understood unless one first learns to comprehend the language and read the characters in which it is written. It is written in the language of mathematics, and its characters are triangles, circles, and other geometric figures without which it is humanly impossible to understand a single word of it; without these one is wandering in a dark labyrinth."

  Urban VIII invited Galileo to papal audiences on six separate occasions, and by these and other means made Galileo feel that there would be no danger in promoting the Copernican view when he came to write out his complete system of the world, the Dialogue Concerning the Two Chief World Systems. Ill health made work on this magnum opus proceed slowly, and Galileo did not complete it until 1630. He tried to get permission to have it published in Rome, and failed; eventually he secured permission for publication in Florence, where it appeared in 1632. The outcome was the trial and condemnation by the Inquisition, and a life sentence of house imprisonment under a guard of officers appointed by the Inquisition.

  Five years after the Dialogue was banned it was published at Leiden under the title Discorsi e dimostrazioni matematiche intorno a due nuove scienze attenenti alia meccanica. Descartes' years in Italy, together with his knowledge of Latin, would have made it an easily accessible read. But he had already read it by then. It did nothing to abate his alarm about the dangers involved in holding the Copernican view. In February 1634 he wrote to Mersenne announcing that, after all, he was not going to send Le Monde, but was go
ing to keep it entirely to himself: "I have decided wholly to suppress the treatise I have written and to forfeit almost all my work of the last four years in order to give my obedience to the Church, since it has proscribed the view that the earth moves. All the same, since I have not yet seen that the proscription has been ratified by the Pope or the Council [it was made by the Congregation of Cardinals set up for the censorship of books], I should be very glad to know what the view in France is on this matter, and whether their authority is enough to make the proscription an article of faith."34

  There was an added worry; the very people—the Jesuits—he most wished to placate and even to enlist on his side were clearly on the side of the Congregation of the Index in this matter. Referring to a book by Scheiner called Rosa Ursina Descartes continued:

  If I may say so, the Jesuits have helped to get Galileo convicted: Father Schemer's entire book shows they are no friends of Galileo's. Besides, the observations which the book contains provide so much proof to dispossess the sun of the motion attributed to it that I cannot believe that Father Scheiner himself does not share the Copernican view in his heart of hearts; and I find this so astonishing that I dare not write down my feelings on the matter.

  As for myself, I seek only repose and peace of mind . . . I am hardly capable of instructing others and especially those who, if the truth were known, would perhaps be afraid of losing the reputation which they have acquired through views that are false.35

  Descartes' disquiet did not stop there. Two months later he was writing to Mersenne again, still in anxious confusion about the Galileo affair, because he thought that his previous letter had gone astray, and that Mersenne would still be in doubt about his attitude—and especially his acute apprehension that he too might fall foul of the Inquisition. In this next letter he showed that he had been debating with himself and others whether the condemnation of Galileo amounted to a statement that the fixity of the earth had been pronounced an article of faith, for, if not, Descartes still had a slim hope of being able to publish his views without fear of censure. But his timidity in the matter proved overwhelming:

  From your last I learn that my last letter to you has been lost . . . [in it] I told you at length the reason why I did not send you my treatise. I am sure you will find it so just that, far from blaming me for resolving never to show it anyone, you would be the first to exhort me to do so, if I were not already fully so resolved.

  Doubtless you know that Galileo was recently censured by the Inquisitors of the Faith, and that his views about the movement of the earth were condemned as heretical. I must tell you that all the things I explained in my treatise, which included the doctrine of the movement of the earth, were so interdependent that it is enough to discover that one of them is false to know that all the arguments I was using are unsound. Though I thought they were based on very certain and evident proofs, I would not wish, for anything in the world, to maintain them against the authority of the Church. I know that it might be said that not everything which the Roman Inquisitors decide is automatically an article of faith, but must first be approved by a General Council. But I am not so fond of my own opinions as to want to use such quibbles to be able to maintain them. I desire to live in peace and to continue the life I have begun under the motto "to live well you must live unseen" . . .

  1. Adrien Baillet (1649-1706), Descartes' first major biographer.

  2. Descartes' birth-place in La Haye, now called Descartes.

  3. King Henri IV of France, reigned 1589-1610, founder of La Fleche school.

  4. The famous Jesuit College of La Fleche where Descartes was educated.

  5. Portrait of the young Rene Descartes, aged about twenty, artist unknown.

  6. View of Breda in the United Provinces, where Descartes briefly served in the army of Prince Maurice of Nassau, and where he met Isaac Beeckman.

  7. Prince Maurice of Nassau (1567-1625), Stadhouder of the United Provinces.

  8. The warlike Duke Maximilian of Bavaria (1581-1662) in whose army Descartes served at the Battle of the White Mountain outside Prague on 8 November 1620.

  9. A stove-heated room with a portrait bust of Descartes, recalling the famous day of discoveries and night of dreams, 10 November 1619.

  10. A Rosicrucian allegory, engraved by Johann Theodore de Bry in the early sixteenth century. The Latin superscription reads, 'the rose gives honey to the bees' — that is: the secrets of the rosy cross are open to those who work hard at discovering them.

  11. The Rosicrucian 'Tree of the Awareness of Good and Evil' in a coloured woodcut from Geheime Figuren der Rosenkreuzer, 1785.

  12. The Rosicrucian Parnassus of knowledge ('mons philosophorum'). The difficulties to be encountered on the way up its steep paths are represented by, among other things, an unfriendly lion. (Also from Geheime Figuren der Rosenkreuzer, 1785.)

  13. The ill-fated Winter King and Queen — Elector Palatine Frederick V with his wife, Elizabeth Stuart, daughter of James I and VI of England and Scotland. This picture depicts their wedding in 1613.

  14. Ferdinand II, Holy Roman Emperor 1617—1637. The large forward-thrusting jaw was an hereditary feature among the Habsburgs, so severe in some cases that members of the family could not eat properly.

  15. Christian of Anhalt (1568-1630), Elector Frederick V's chief minister, defeated at the Battle of the White Mountain in 1620.

  16. The Battle of the White Mountain, 8 November 1620, at which Duke Maximilian, on behalf of the Emperor Ferdinand II, defeated Elector Frederick V. This battle marks the opening of the Thirty Years War.

  17. Mann Mersenne (1588-1648) Descartes' friend, and the centre of a Europe-wide nexus of scientific and philosophical correspondence.

  18. The city of Leiden, 'the Dutch Athens'. The free Netherlands became Descartes' home from 1628 onwards.

  19. The University of Leiden, where Descartes' theories were the subject of bitter battles between his supporters and opponents.

  20. The frontispiece of Descartes' Discourse de la Methode (1637) in an edition of 1710.

  21. The first page of Descartes' Discourse de la Methode.

  22. An engraved representation of Descartes' theory of the universe, by Alain Manesson Maillet in 1683.

  23. An illustration from 'La Dioptrique' in the Discourse de la Methode.

  24. The numerous family of Elector Frederick of the Palatinate, among them — as a young girl - the brilliant Princess Elizabeth with whom Descartes corresponded.

  25. The infant genius of Blaise Pascal (1623—1662) prompted him to do mathematics wherever and whenever he could.

  26. Pierre de Fermat (1601-1665), Descartes' great - and greater — rival as a mathematician.

  27. Amsterdam in the seventeenth century, the Dutch Golden Age. For most of his time in the Netherlands Descartes lived within easy travelling distance of the city.

  28. An illustration from Descartes' Treatise on Man showing transmission of sensory input by nerves to the brain.

  29. A page from Descartes' 'De Homine Figure'.

  30. An illustration from the Treatise on Man.

  31. Descartes'theory of vision graphically represented in the Treatise on Man.

  32. The anatomy of the brain in an illustration from Descartes' 'De Homine Figure.'

  33. Queen Christina of Sweden.

  34. Descartes explaining something from one of his books to Queen Christina at the Court in Stockholm.

  35. The best-known portrait of Descartes, by Frans Hals. It hangs in the Louvre in Paris.

  36. A less well known and much kinder portrait of Descartes, by Sebastian Bourdon. Unless it is a posthumous evocation of Descartes based on other portraits, it was probably done in the mid or late 1640s.

  37. A fanciful mid-nineteenth century depiction of Descartes musing in Amsterdam, by Felix Philippoteaux.

  38. The genius as hero: Descartes in marble.

  As for what it is that causes a stone one has thrown to stop moving, that is quite clear: it is air res
istance, something one can easily feel. But the reason why a bent bow springs back is more difficult, and I cannot explain it without referring to the principles of my philosophy, which I think I must keep quiet about from now on . . . 36

  Unable to let the matter rest, after discussing some other matters Descartes returned to the troubling theme of Galileo's condemnation, this time in a state of deep disquiet over the fact that his own endeavour to disguise his views by representing them as being about an imaginary world in which purely mechanical laws govern, seemed doomed to fail:

  As for the result you tell me of Galileo's experiments, I deny them all; but I do not conclude the motion of the earth to be any less probable . . . I am astonished that an ecclesiastic should dare to write about the motion of the earth, whatever excuses he may have. For I have seen letters patent about Galileo's condemnation, printed at Liege on 20 September 1633, which contained the words "though he pretended to put forward his view only hypothetically"; thus they seem to forbid even the use of this hypothesis in astronomy. For this reason I do not dare to tell [a certain correspondent] any of my thoughts on the topic. Moreover I do not see that this censure has been endorsed by the Pope or any Council, but only by a single congregation of the Cardinals of the Inquisition; so I do not altogether lose hope that the case may turn out like that of the Antipodes, which were similarly condemned long ago. So in time my World may yet see the light of day; and in that case I will need my own arguments to use myself.37