“In the beginning of the year 1665, I found the method of approximating series and the Rule for reducing any dignity of any Binomial into such a series. The same year in … November had the direct method of Fluxions, and in January had the Theory of Colours, and in May following I had entrance into the inverse method of Fluxions. And the same year I began to think of the orb of the Moon … from Kepler’s Rule of the periodical times of the Planets … I deduced the forces which keep the Planets in their orbs must be reciprocally as the squares of their distances from the centres about which they revolve … All this was in the two plague years of 1665 and 1666, for in those days I was in the prime of my age for invention, and minded Mathematics and Philosophy more than any time since.”