over the whole period, and are particularly frequent in the latter half. The majority of them are addressed to Mersenne, and deal with problems of physics and musical theory (in which he took a special interest). Mathematical subjects are a common topic. Several letters between 1643 and 1649 are addressed to the Princess Elizabeth, the eldest daughter of the ejected elector palatine, who lived at the Hague, where her mother maintained the semblance of a royal court. The princess was obliged to quit Holland, but kept up a philosophical correspondence with Descartes. It is to her that the Principles of Philosophy were dedi cated; and in her alone, according to Descartes, were united those generally separated talents for metaphysics and for mathematics which are so characteristically co-operative in the Cartesian system. Two Dutch friends, Zuylichem, the father of the more celebrated Huyghens, and Hoogheland, figure amongst the correspondents, not to mention various savants, professors, and churchmen (particularly Jesuits). His residence in the Netherlands fell on the most pros perous and brilliant days of the Dutch state, under the stadtholdership of Frederick Henry (1625-1647). Abroad its navigators monopolized the commerce of the world, and explored unknown seas ; at home the Dutch school of painting reached its acme in Rembrandt (1607-1669) ; and the philological reputation of the country was sustained by Grotius, Vossius, and the elder Heinsius. And yet, though Rembrandt s Nightwatch is dated the very year after the publication of the Meditations, not a word in Descartes breathes of any work of art or historical learning. The contempt of aesthetics and erudition is characteristic of the most typical members of the Cartesian school, especially Malebranche. Though Descartes probably read more than some of his admirers supposed he was not in any strict sense a reader. His wisdom grew mainly out of his own rellections and experiments, calmly yet ceaselessly pursued. Of mere learning and scholarship he had no esteem. The story of his disgust, when be found that Queen Christina devoted some time every day to the study of Greek under the tuition of Vossius, is at least true in substance. 1 It gives no evidence of science, he remarks, to possess a tolerable knowledge of the Roman tongue, such as once was possessed by the populace of Rome. 2 In all his travels, and in the different places at which he settled, his interest seems untouched either by art or history ; he looks only to the phenomena of nature and the actual aspects of human life. He was a spectator rather than an actor on the stage of the world. If he entered the army, it was merely bscause the position gave a vantage-grouud from which to make his obser vations. In the political interests which these contests involved he took no part ; his favourite disciple, the Princess Elizabeth, was the daughter of the banished king, against whom he had served in Bohemia ; and Queen Christina, his second royal follower, was the daughter of Gustavus Adolphus. In many ways Descartes is a type of that self-reliant, harsh, and abstract spirit of science to which erudition and all the heritage of the past seem but elegant and un worthy trifling. The science of Descartes was physics in all its branches, but especially as applied to physiology. Science, he says, may be compared to a tree ; metaphysics is the root, physics is the trunk, and the three chief branches are mechanics, medicine, and morals, the three applications of our knowledge to the outward world, to the human body, and to the conduct of life. 3 Such then was the work, and such the ends, that Descartes had iu view in Holland. His residence was generally divided into two parts one his workshop for 1 (Euvr. x. 375. a (Euvr. ix. 6. * (Euvr. iii. 24. science, the other his reception-room for society. " Here are my books," he is reported to have told a visitor, as he pointed to the animals he had dissected. " I am now," he writes in 1630, " studying chemistry and anatomy together ; and every day I learn something which I could not find in books." 4 He is working hard at his book on refraction, and at the same time is busy dis secting the hends of different animals in order to explain imagination and memory, which he considers physical pro cesses. 5 It need not from this be supposed that Descartes was a laborious student. " I can say with truth," he writes to the Princess Elizabeth, 6 " that the principle which 1 have always observed in my studies, and which I believe has helped me most to gain what knowledge I have, has been never to spend beyond a very few hours daily in thoughts which occupy the imagination, and a very few hours yearly in those which occupy the understanding, and to give all the rest of my time to the relaxation of the senses and the repose of the mind." But his expectations from the study of ana tomy and physiology went a long way. " The conservation of health," he writes in 1646, " has always been the principle end of my studies." 7 In 1629 he asks Mersenne to take care of himself " till I find out if there is any means of getting a medical theory based on infallible demonstrations, which is what I am now inquiring." 8 And to Zuylichen he writes in 1638. 9 " I have never taken so much care of myself as at present ; and whereas I used to think that death could take from me only thirty or forty years at most, it could not overtake me now without depriving me of the hope of more than a century." And similar views seem to have been expressed by him to Sir Kenelm Digby, who visited him in Holland. Astronomical inquiries in connection with optics, meteorological phenomena, and, in a word, the whole field of natural laws, excited his desire to explain them. His own observation, and the reports of Mersenne, furnished his data. Of Bacon s demand for observation and collection of facts he is an imitator ; and he wishes (in a letter of 1632) that " some one would undertake to give a history of celestial phenomena after the method of Bacon, and describe the sky exactly as it appears at present, without introducing a single hypothesis." 10 He had several writings in hand during the early years of his residence in Holland, but the main work of this period was a physical doctrine of the universe which he termed The World. Shortly after his arrival he writes to Mersenne that it will probably be finished in 1633, but meanwhile asks him not to disclose the secret to his Parisian friends. Already anxieties appear as to the theological verdict upon two of his fundamental views the infinitude of the universe, and the earth s lotation round the sun. 11 But towards the end of year 1633 we find him writing as follows : 12 "I had intended sending you my World as a New Year s gift, and a fortnight ago I was still minded to send you a fragment of the work, if the whole of it could not be transcribed in time. But I have just been at Leyden and Amsterdam to ask after Galileo s cosmical system, as I imagined I had heard of its being printed last year in Italy. I was told that it had been printed, but that every copy had been at the same time burnt at Rome, and that Galileo had been himself con demned to some penalty." He has also seen a copy of Galileo s condemnation at Lie ge (20th September 1633), with the words " Although he professes that the (Coper- nican) theory was only adopted by him as a hypothesis." His friend Beeckman lent him a copy of Galileo s work, 4 CEuvr. ri. 101. B (Euvr. vi. 234. (Euvr. ix. 131. 7 (Euvr. ix. 341. 8 (Euvr. vi. 89. (Euvr. vii. 412. 10 (Euvr. vi. 210. 11 (Euvr. vi. 73. 15 (Euvr. vi. 239.
