Newton's name, attacked so violently by Berkeley in his Defence of Free Thinking in Mathematics, was still deplored twenty years later by eager inquirers such as George Horne: “The prejudice for Sir Isaac has been so great, that it has destroyed the intent of his undertaking, and his books have been a means of hindering that knowledge they were intended to promote. It is a notion every child imbibes almost with his mother's milk, that Sir Isaac Newton has carried philosophy to the highest pitch it is capable of being carried, and established a system of physics upon the solid basis of mathematical demonstration."? Such representative quotations disclose the creation, under Newton's leadership, of a new background in the minds of Europe's intelligentsia such that all problems must have been viewed afresh because they were seen against it. A student of the history of physical science will assign to Newton a further importance which the average man can hardly appreciate. He will see in the English genius a leading figure in the invention of certain scientific tools necessary for fruitful further development such as the infinitesimal calculus. He will find in him the first clear statement of that union of the experimental and mathematical methods which has been exemplified in all subsequent discoveries of exact science. He will note the separation in Newton of positive scientific inquiries from questions of ultimate causation. Most important, perhaps, from the point of view of the exact scientist, Newton was the man who took vague terms like force and mass and gave them a precise meaning as quantitative continua, so that by their use the major phenomena of physics became amenable to mathematical treatment. It is because of these remarkable scientific performances that the history of mathematics and mechanics for a hundred years subsequent to Newton appears primarily as a period devoted to the assimilation of his work and A Fair, Candid, and Impartial State of the Case between Sir Isaac Newton and Mr Hutchinson, Oxford, 1753. P. 72. the application of his laws to more varied types of phenomena. So far as objects were masses, moving in space and time under the impress of forces as he had defined them, their behaviour was now, as a result of his labours, fully explicable in terms of exact mathematics. It may be, however, that Newton is an exceedingly important figure for still a third reason. He not only found a precise mathematical use for concepts like force, mass, inertia ; he gave new meanings to the old terms space, time, and motion, which had hitherto been unimportant but were now becoming the fundamental categories of men's thinking. In his treatment of such ultimate concepts, together with his doctrine of primary and secondary qualities, his notion of the nature of the physical universe and of its relation to human knowledge (in all of which he carried to a more influential position a movement already well advanced) -in a word, in his decisive portrayal of the ultimate postulates of the new science and its successful method as they appeared to him, Newton was constituting himself a philosopher rather than a scientist as we now distinguish them. He was presenting a metaphysical groundwork for the mathematical march of mind which in him had achieved its most notable victories. Imbedded directly and prominently in the Principia, Newton's most widely studied work, these metaphysical notions were carried wherever his scientific influence penetrated, and borrowed a possibly unjustified certainty from the clear demonstrability of the gravitational theorems to which they are appended as Scholia. Newton was unrivalled as a scientist-it may appear that he is not above criticism as a metaphysician. He tried scrupulously, at least in his experimental work, to avoid metaphysics. He disliked hypotheses, by which he meant explanatory propositions which were not immediately deduced from phenomena. At the same time, following his illustrious predecessors, he does give or assume definite answers to such fundamental questions as the nature of space, time, and matter; the relations of man with the objects of his knowledge; and it is just such answers that constitute metaphysics. The fact that his treatment of these great themes-borne as it was over the educated world by the weight of his scientific prestige-was covered over by this cloak of positivism, may have become itself a danger. It may have helped not a little to insinuate a set of uncritically accepted ideas about the world into the common intellectual background of the modern man. What Newton did not distinguish, others were not apt carefully to analyse. The actual achievements of the new science were undeniable ; furthermore, the old set of categories, involving, as it appeared, the now discredited medieval physics, was no longer an alternative to any competent thinker. In these circumstances it is easy to understand how modern philosophy might have been led into certain puzzles which were due to the unchallenged presence of these new categories and presuppositions. Now a penetrating study of post-Newtonian philosophers quickly reveals the fact that they were philosophizing quite definitely in the light of his achievements, and with his metaphysics especially in mind. At the time of his death Leibniz was engaged in a heated debate on the nature of time and space with Newton's theological champion, Samuel Clarke. Berkeley's Commonplace Book and Principles, still more his lesser works such as The Analyst, A Defence of Free Thinking in Mathematics, and De Motu, show clearly enough whom he conceived to be his deadly foe. Hume's Enquiry Concerning Human Understanding and Enquiry Concerning the Principles of Morals contain frequent references to Newton. The French Encyclopædists and materialists of the middle of the eighteenth century felt themselves one and all to be more consistent The fullest edition of Berkeley's Works is that of A. C. Fraser, Oxford, 1871, 4 vols. Newtonians than Newton himself. In his early years Kant was an eager student of Newton, and his first works aim mainly at a synthesis of continental philosophy and Newtonian science. Hegel wrote1o an extended and trenchant criticism of Newton. Of course, these men do not accept Newton as gospel truth-they all criticize some of his conceptions, especially force and space-but none of them subjects the whole system of categories which had come to its clearest expression in the great Principia to a critical analysis. It may be that their failure to construct a convincing and encouraging philosophy of man is due in large part to this untested remainder. It may be that many of the terms and assumptions in which their thinking proceeded were in their unanalysed form essentially refractory to any such brilliant achievement. The only way to bring this issue to the bar of truth is to plunge into the philosophy of early modern science, locating its key assumptions as they appear, and following them out to their classic formulation in the metaphysical paragraphs of Sir Isaac Newton. The present is a brief historical study which aims to meet this need. The analysis will be sufficiently detailed to allow our characters to do much speaking for themselves, and to lay bare as explicitly as possible the real interests and methods revealed in their work. At its close the reader will understand more clearly the nature of modern thinking and judge more accurately the validity of the contemporary scientific world-view. Let us start our inquiry with certain questions suggested by the work of the first great modern astronomer and the founder of a new system of the celestial orbs, Nicholas Copernicus. See especially his Thoughts on the True Estimation of Living Forces. 1746; General Physiogony and Theory of the Heavens, 1755; Monadologia Physica, 1756; and Inquiry into the Evidence of the Principles of Natural Theology and Morals, 1764; in any edition of his works. 10 Hegel, Phenomenology of Mind (Baillie trans), London, 1910, Vol. I, pr. 124, ff., 233ff, Philosophy of Nature, passim; and History of Philosophy (Haliane trans.), Vol. III. 322, ff, CHAPTER II COPERNICUS AND KEPLER (A) The Problem of the New Astronomy WHY did Copernicus and Kepler, in advance of any empirical confirmation of the new hypothesis that the earth is a planet revolving on its axis and circling round the sun, while the fixed stars remain at rest, believe it to be a true picture of the astronomical universe? This is historically the most convenient question with which to open our attack. By way of preparing an answer to this question let us ask another, namely what ground a sane, representative thinker, contemporary to Copernicus, would have for rejecting this new hypothesis as a piece of rash and quite unjustified apriorism? We are so accustomed to think of the opposition to the great astronomer as being founded primarily on theological considerations (which was, of course, largely true at the time) that we are apt to forget the solid scientific objections that could have been, and were, urged against it. First of all, there were no known celestial phenomena which were not accounted for by the Ptolemaic method with as great accuracy as could be expected without more modern instruments. Predictions of astronomical events were made which varied no more from the actual occurrence than did predictions made by a Copernican. And in in astronomy, as elsewhere, possession is nine-tenths of the law. No sensible thinker would have abandoned a hoary, time-tested theory of the universe in favour of a new-fangled scheme unless there were important advantages to be |