Some quotations by Newton

The way therefore to examin it is by considering whether the experiments which I propound do prove those parts of the Theory to which they are applyed, or by prosecuting other experiments which the Theory may suggest for its examination.

Newton to Oldenburg, 6 July 1672; Corres 1, 210

What Des-Cartes did was a good step. You have added much several ways, & especially in taking y^e colours of thin plates into philosophical consideration. If I have seen further it is by standing on y^e shoulders of Giants.

Newton to Hooke, 5 Feb. 1676; Corres 1, 416. There is also a detailed discussion of the context of this statement.

For it is not number of Experiments, but weight to be regarded; & where one will do, what need of many?

Newton to Oldenburg, 18 Aug. 1676; Corres 2, 79

'Tis the truth of my experiments which is the business in hand. On this my Theory depends, & which is of more consequence, the credit of my being wary, accurate and faithfull in the reports I have made.

Newton to Oldenburg, 28 Nov. 1676; Corres 2, 183

Or it may be in the nature of bodies not only to have a hard and impenetrable nucleus but also a certain surrounding sphere of most fluid and tenuous matter which admits other bodies into it with difficulty.

From ``De aere et aethere'', translated in pp221-4, Unpublished Scientific Papers of Isaac Newton ed A.R. Hall and Marie Boas Hall (Cambridge, 1962)

Nature is exceedingly simple and conformable to herself. Whatever reasoning holds for greater motions, should hold for lesser ones as well. The former depend upon the greater attractive forces of larger bodies, and I suspect that the latter depend upon the lesser forces, as yet unobserved, of insensible particles. For, from the forces of gravity, of magnetism and of electricity it is manifest that there are various kinds of natural forces, and that there may be still more kinds is not to be rashly denied. It is very well known that greater bodies act mutually upon each other by those forces, and I do not clearly see why lesser ones should not act on one another by similar forces.

From ``De aere et aethere'' (Halls p333)

Mathematicians that find out, settle & do all the business must content themselves with being nothing but dry calculators & drudges & another that does nothing but pretend & grasp at all things must carry away all the invention as well of those that were to follow as of those that went before.

Newton to Halley; Corres 2, 435

I keep the subject constantly before me and wait till the first dawnings open slowly, by little and little, into a full and clear light.

Biographia Britannica (London, 1760), 5, 3241

I don't know what I may seem to the world, but, as to myself, I seem to have been only like a boy playing on the sea shore, and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me.

From Spence's Anecdotes (1820) and attributed to Andrew Michael Ramsay.