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comparison with that which still remained within the sphere of their unfulfilled aspirations. That Newton constantly kept back his investigations, because they were not as complete as he desired to make them, is certain from the history of the publications which were almost dragged from him by his friends, and from his own repeated declarations. But this feeling was not the modesty which would rank his own labours below the inferior work of other minds. It is one thing to withhold a scientific theory because it is thought unworthy of the world, and quite another to keep it in reserve until it should be made more worthy of the philosopher's own aspirations. If this feeling is what Sir David Brewster points at when he speaks of Newton's modesty, we accept the explanation, but we protest against the notion that it is any compliment to the memory of a great genius to hint that he knew not the value of his own work; and in the case of Newton the suggestion of any such feeble virtue (if virtue it is) seems to us peculiarly misplaced.
To take, for example, the great discoveries which were at length published in the 'Principia,' is it conceivable that, after having solved the greatest of all the problems at which the world had been working from the first birth of science, Newton should have imagined that he had produced nothing of such importance as to deserve the attention of men of science? Yet he had completed the demonstrations of the law of elliptic motion years before he made them known; and it was only on the appeal of Halley, who had in vain sought the solution from Hooke and Wren, that Newton announced that he had long since ascer tained that the orbit round a centre of force varying inversely as the square of the distance would be an ellipse. To Halley's urgency alone was due the communication to the Royal Society of the treatise which formed the germ of the Principia.' There is a passage, indeed, in a subsequent letter to Halley, which gives some apparent countenance to the notion that Newton had thought slightingly of his demonstrations of the forces of orbits, and had thrown them by, being upon other studies;' but it harmonises much better with the general character of Newton's mind to suppose that he regarded his inquiries as incomplete so long as his first idea of universal gravitation seemed incapable of proof. It was strange that Picard's corrected measurement of a degree should not earlier have attracted Newton's attention, though probably this arose from his attention having been concentrated at that time on his optical investigations; but on resuming his old calculations on this improved basis in 1684, the results agreed, with an exactness which satisfied him, that the force which kept the moon in her orbit was identical with terres.
trial gravity. From the moment when his theory was thus substantially completed there is no trace of any hesitation to make his discoveries public. The two following years were devoted to the composition of the Principia,' in which the principles of the preliminary treatise were developed into a complete system of physical astronomy, which was immediately sent to the Royal Society and published by their direction.
The long delay in the publication of his Optics gives even less countenance to the theory of an unintelligible modesty. At last the work was, in Newton's judgment and in fact, incomplete in many respects, and the leading discoveries had long since been made public through the Royal Society, and had led to discussions which were not calculated to invite fresh conflict with the world. But it is mainly with reference to the method of fluxions that Newton's modesty has sometimes been called in aid to account for the silence which he had preserved as to the possession of this powerful engine of investigation, a silence by which he exposed his title as the first inventor to attacks which could not have been made if he had frankly communicated from time to time the additions which he was making to the armoury of mathematical science.
The earliest manuscripts on this subject date as far back as 1665 and 1666, but it was not till 1669 that a paper on analysis by infinite series was communicated to Barrow and Collins. Two years later Newton doled out to Collins a little more information as to his methods, in the famous letter of the 10th of December, 1672, which afterwards became the backbone of the charge of plagiarism brought against Leibnitz, to whom an abridgment of the letter had been sent in 1676. But even up to this date a general statement of the process was studiously withheld; and not only were the details of the calculus kept in obscurity, except with reference to some special cases, but the bare statement of the problem to be solved was thought too precious to be communicated, except under the disguise of an unintelligible cypher. When afterwards deciphered by Newton himself, the mysterious sentence proved to be 'Data æquatione quotcunque fluentes quantitates involvente fluxiones invenire et vice versa,' which, if originally given at length, would have shown the grand problem which Newton had solved, but not the general method by which he treated it. A little more information was allowed to leak out in some observations communicated to Wallis and incorporated in his Algebra in 1692. It is probable that the method itself would never have been published in Newton's lifetime but for the necessity of vindicating himself against the accusation of having borrowed his ideas from Leib
nitz, and establishing the priority of his own discovery. This was done in 1704; and it is impossible to suppose that during all those years, when the method had borne its glorious fruit in the demonstrations of the Principia,' Newton was unconscious of the immense value of the new analysis. The only real difficulty in assigning a motive for so determined a concealment of the processes he employed is in saying how far the delay was due to the hope of bringing the calculus to still greater perfection, and how far it resulted from the disposition, then almost universal among philosophers, to publish nothing but results, and to keep to themselves their processes as the means of gaining further triumphs over rivals who were not possessed of methods of equal power. This last was the motive which the practice of the time would most readily suggest. When a philosopher in those days had solved a new problem of especial difficulty, the first thing which he generally did was to propose it as a challenge to the world; and those who found the answer commonly contented themselves with stating the result, without the slightest intimation of the process by which it had been reached. Even such solutions were frequently announced under some disguise, which could perhaps be penetrated by those who had already solved the problem, but would convey no information to assist less successful competitors. The whole tone of scientific society was infected with a love of triumph which was not then thought unworthy of being preferred to the simple interests of truth. It is not possible altogether to ignore the prevalence of this strong competitive principle in estimating the causes of Newton's reserve, but even the least partial critics have been compelled to admit that Newton was less chargeable with excessive emulation than any of his rivals, and that a much more probable and much more worthy explanation is found in his reluctance to publish any imperfect essays, coupled perhaps with a dread of resuming the unpleasant controversies which his first optical discoveries had occasioned.
It is not necessary to discuss the minor contributions of Newton to other branches of science to see to what extent and on what grounds the common faith in his supremacy is confirmed by the consent of the scientific world. It is enough to examine his leading discoveries to be satisfied that the position which the most critical examination of his claims assigns to him is not less exalted than that which his name has occupied in the minds of his countrymen of his own and every succeeding generation. It is not mere national complacency which has elevated Sir Isaac Newton above all the explorers of nature; and if the motives for this admiration take a slightly different shape within and without
the widening circle of scientific knowledge, the sentiment of Newton's countrymen is in strict harmony with the judgment of the world of science, which no longer knows those distinctions of nationality which in Newton's days it had not learned to disregard.
The theological tenets of our philosopher we are not anxious now to examine. He has been claimed alike as an orthodox defender of the doctrines of the Church and as a convert to the Arian views which so strongly prevailed during the period of his life. The truth certainly is intermediate to these extreme views, but the precise dogmas of the philosopher's creed are not, perhaps, to be gathered from the records which remain. That which gives the character to his theological inquiries is the genuine tolerance and simple reverence which were instinctive to him, and the sincerity with which in the interests of truth he attacked every dishonest argument, whatever might be its bearing on the religious controversies of the day. This is what we might expect to find in the chief interpreter of nature, and, satisfied with this, we may leave the lovers of sectarian controversy, if they please, to claim the prestige of Newton's name for the special tenets of their own communion. His pertinent quary on the word oμoovoios, whether Christ sent his apostles to preach metaphysics to the unlearned common people and to their wives and children,' his criticism on the history of the Athanasian controversy, and his demolition of the spurious verse on the three witnesses, are far from proving that Newton had adopted Arian views in their full extent; and in the most formal statement of his religious opinions which he left behind him, we have a scheme of theology at least as far removed from Socinian as from orthodox doctrines.
It has often been said that in Newton's case the country for once remembered the duty which she owed to science. The philosopher was not left, as so many votaries of science have been, to die in poverty. He was placed in a position of dignity and wealth, in which, without cramping his abundant liberality, he was able to accumulate a considerable fortune. But there is not much room in this for national complacency. It was as the friend of Montague, not as the author of the Principia,' that Newton obtained his office at the Mint; and though the occupation, especially at that time, was not uncongenial to a scientific mind, it may be doubted whether the world did not lose more than Newton gained by the appointment. To make a great philosopher Master of the Mint was not quite so incongruous as giving a gaugership to a distinguished poet; but it was an error of the same kind, and was probably as injurious to the cause of science
as if the reward of Newton had been, like the preferment of Burns, something ludicrously inappropriate. Certain it is that Newton stopped in his career of discovery at an age when some of the greatest ornaments of science commenced their labours. With the exception of one or two brilliant feats-as when he solved Bernoulli's problems, and at a later period answered the challenge of Leibnitz in an evening's work, after returning from his official duties at the Mint-little that was new in science came from the translated philosopher, unless we are to attribute to that period some part of the improvement of his lunar theory, which involved him in his dispute with the impracticable Flamsteed, and was the only effort, as he himself declared, that ever cost him a headache. The anxiety which he expressed not to make himself too prominent in science, lest he should seem to be neglecting the King's business, was probably strengthened by his memorable custom of never touching a subject to which he was not able to devote his whole powers and his whole time.
One of many evidences of this habit of mind is found in a letter to Flamsteed, in which Newton says:- When I set myself wholly to calculations, I can endure them, and go through them well enough; but when I am about other things (as at present), I can neither fix to them with patience nor do them without errors, which makes me let the moon's theory alone at present, with a design to set to it again and go through it at once.'
To a man of this temperament-and to no other could the career of discovery which Newton ran have been possible-an appointment involving continuous duties was the death-blow to his scientific activity. The strange and sudden cessation in Newton's course has sometimes been accounted for by a hypothesis, which was eagerly welcomed by those who wished to discredit his theological inquiries, and the only defect of which was, that it was wholly unsupported, or, more correctly speaking, absolutely contradicted by the facts of his life. For a few days, in the autumn of 1693, Newton, who had been suffering from an epidemic, aggravated by long-continued work, became decidedly light-headed. Two strange letters, one to Pepys, and the other to Locke, remain as evidence of this temporary affection. The rumour that Newton's brain was giving way spread over the Continent; and long after the philosopher had recovered his usual health, the story, in a grossly exaggerated form, found its way into the diary of Huyghens, who had picked it up from a Scotchman, of whom he did not know enough to give his name correctly. On this slender basis a theory was built up by M. Biot, that Newton's abandonment of philosophy for religion was the result of a permanent affection of the brain, amounting to something like in