Were it possible to trace the succession of ideas in the mind of Sir Isaac Newton, during the time that he made his greatest discoveries, I make no doubt but our amazement at the extent of his genius would a little subside. But if, when a man publishes discoveries, he, either through design, or through habit, omit the intermediate steps by which he himself arrived at them; it is no wonder that his speculations confound others... [W]here we see him most in the character of an experimental philosopher, as in his optical inquiries... we may easily conceive that many persons, of equal patience and industry... might have done what he did. And were it possible to see in what manner he was first led to those speculations, the very steps by which he pursued them, the time that he spent in making experiments, and all the unsuccessful and insignificant ones that he made in the course of them; as our pleasure of one kind would be increased, our admiration would probably decrease. Indeed he himself used candidly to acknowledge, that if he had done more than other men, it was owing rather to a habit of patient thinking, than to any thing else. ...[T]he interests of science have suffered by the excessive admiration and wonder, with which several first rate philosophers are considered; and... an opinion of the greater equality of mankind, in point of genius, and powers of understanding, would be of real service in the present age.

Of these massive achievements I shall single out two. One is Newton’s working out of the concept of the cause, by making it over from its scholastic form in, say, St. Thomas Aquinas, to the modern form which now seems so obvious to us. This is one theme in this chapter. But I shall go to it by way of a related achievement, and to my mind one which is as remarkable: the marriage of the logical with the empirical method.

The goal of deriving all the phenomena of nature from a few basic physical laws and the axioms of mathematics had been set by Galileo...
In studying curvilinear motions on the earth Galileo had found the parabola to be the basic curve. In the heavens... Kepler... had found the ellipse to be the basic curve. Why this difference? ...since parabola and ellipse are both conic sections there was the provocative suggestion that perhaps some physical law unified these related paths of motion. ...
It has often happened in the history of mathematics and science that major problems remained outstanding... great minds... succeeded only in revealing the true difficulties... and in generating an atmosphere of dispair... Then a genius appeared... with ideas that seemed remarkably simple once propounded, clarified the entire situation, dispelled the confusion, restored order, and produced a new synthesis that embraced far more even than the phenomena under consideration. The genius who... picked up the torch of science dropped by Galileo, was Isaac Newton.

When asked how he accomplished his astonishing discoveries, Newton replied unhelpfully, “By thinking upon them.

Newton achieved the clearest appreciation of the relation between the empirical elements in a scientific system and the hypothetical elements derived from a philosophy of nature.

Bohr's investigation had typified what had become a standard procedure in problems of theoretical physics. The first step was to discover the mathematical laws governing certain groups of phenomena; the second was to devise hypothetical models or pictures to interpret these laws in terms of motion or mechanism; the third was to examine in what way these models would behave in other respects, and this would lead to prediction of other phenomena-predictions which might or might not be confirmed when put to the test of experiment. For instance, Newton had explained the phenomena of gravitation in terms of a force of gravitation; a later age had seen the luminiferous ether introduced to explain the propagation of light and, subsequently, the general phenomena of electricity and magnetism; finally Bohr had introduced electronic jumps in an attempt to explain atomic spectra. In each case the models had fulfilled their primary purpose, but had failed to predict further phenomena with accuracy.

Not long after, that Great Geometrician, the Illustrious Newton, writing his Mathematical Principles of Natural Philosophy, demonstrated not only that what Kepler had found, did necessarily obtain in the Planetary System; but also, that all the Phænomena of Comets wou'd naturally follow from the same Principles; which he abundantly illustrated by the Example of the aforesaid Comet of the Year 1680, shewing, at the same time, a Method of Delineating the Orbits of Comets Geometrically; wherein he (not without the highest Admiration of all Men) solv'd a Problem, whose Intricacy render'd it worthy of himself. This Comet he prov'd to move round the Sun in a Parabolical Orb, and to describe Area's (taken at the Center of the Sun) proportional to the Times.

I start with the simplest phenomena... the first... is the phenomena of light. Early on, when light was being investigated by Newton, he thought that the light that came into the eye was like a rain of particles, like rain drops... [M]ore light meant more particles... and one kind of color light would one kind of rain drop and another... would be a different kind of rain drop... over the whole spectrum... and if we would some day have sufficiently delicate instruments, we would presumably discover that it was like a pattering... [I]t would go click, click, click when the particles came raining down. ...He also discovered ...the light from the soap bubbles or light from thin films... The brightness of reflection... depends on how thick the film is. As the film gets thicker and thinner, it gets brighter and darker. That was hard for him to understand from the point of view of particles. Finally a theory of waves was invented which explained that very easily... until we measured light very precisely... and lo and behold, to our horror, it behaved like particles.

What is the scientific method, and when, where, and how did it become, as the kids say, a thing? Authoritative definitions of “the scientific method” often state that it consists of a set of procedures including observation, experimentation, and the formation and testing of hypotheses by inductive and deductive reasoning. Such accounts, as a rule, ascribe science’s successes to the application of these procedures ever since the seventeenth century and the work of people such as Francis Bacon and Isaac Newton. But neither Bacon nor Newton nor anyone else in the seventeenth century would have recognized the phrase; moreover, neither would have agreed with current standard definitions. Bacon, for instance, rejected deductive reasoning as the bad old Aristotelian approach, and Newton, author of one of the boldest hypotheses in the history of science—the universal aether—denied any role for hypotheses in his science, famously declaring “hypotheses non fingo” (I frame no hypotheses).

I believe that the clue to his mind is to be found in his unusual powers of continuous concentrated
introspection. A case can be made out, as it also can with Descartes, for regarding him as an accomplished
experimentalist. Nothing can be more charming than the tales of his mechanical contrivances when he was a
boy. There are his telescopes and his optical experiments, These were essential accomplishments, part of his
unequalled all-round technique, but not, I am sure, his peculiar gift, especially amongst his contemporaries.
His peculiar gift was the power of holding continuously in his mind a purely mental problem until he had
seen straight through it. I fancy his pre-eminence is due to his muscles of intuition being the strongest and
most enduring with which a man has ever been gifted. Anyone who has ever attempted pure scientific or
philosophical thought knows how one can hold a problem momentarily in one's mind and apply all one's
powers of concentration to piercing through it, and how it will dissolve and escape and you find that what
you are surveying is a blank. I believe that Newton could hold a problem in his mind for hours and days and
weeks until it surrendered to him its secret. Then being a supreme mathematical technician he could dress it
up, how you will, for purposes of exposition, but it was his intuition which was pre-eminently extraordinary
- 'so happy in his conjectures', said De Morgan, 'as to seem to know more than he could possibly have any
means of proving'. The proofs, for what they are worth, were, as I have said, dressed up afterwards - they
were not the instrument of discovery.

Ever since Sir Isaac Newton's times, scientists have worked in the same sort of way:

Although many historians of the new millennium now take issue with the notion of a Scientific Revolution, it is generally agreed that Newton's work culminated the long development of European science, creating a synthesis that opened the way for the scientific culture of the modern age.

Isaac Newton’s Philosophae Naturalis Principia Mathematica abstracted time from events, establishing its tractability to scientific calculation. Conceived as pure, absolute duration, without qualities, it conforms perfectly to its mathematical idealization (as the real number line). Since time is already pure, its reality indistinguishable from its formalization, a pure mathematics of change – the calculus – can be applied to physical reality without obstruction. The calculus can exactly describe things as they occur in themselves, without straying, even infinitesimally, from the rigorous dictates of formal intelligence. In this way natural philosophy becomes modern science.

In writing Newton's biography, I have attempted, in accordance with my understanding of biography as a literary form, to avoid composing an essay on Newtonian science. At the same time I have sought to make Newton the scientist the central character of my drama.