“… leaders who forbid their followers to use effective contraceptive methods … express a preference for "natural" methods of population limitation, and a natural method is exactly what they are going to get. It is called starvation.”

This has also appeared in the alternate form: "What we observe is not nature itself, but nature exposed to our method of questioning."
Physics and Philosophy (1958)
Variant: What we observe is not nature itself, but nature exposed to our method of questioning.
Source: Physics and Philosophy: The Revolution in Modern Science

Query 31
Opticks (1704)

Quote from his autobiography,Unfinished Journey”
Violinist Yehudi Menuhin

Source: The Light of Day (1900), Ch. IV: Natural Versus Supernatural

Nicomachus of Gerasa: Introduction to Arithmetic (1926)
Context: All that has by nature, with systematic method, been arranged in the universe, seems both in part and as a whole to have been determined and ordered in accordance with number, by the forethought and the mind of him that created all things; for the pattern was fixed, like a preliminary sketch, by the domination of number preëxistent in the mind of the world-creating God, number conceptual only and immaterial in every way, but at the same time the true and the eternal essence, so that with reference to it, as to an artistic plan, should be created all these things: time, motion, the heavens, the stars, all sorts of revolutions.<!--Book I, Chapter VI

Source: 1850s, An Investigation of the Laws of Thought (1854), p. 1; Ch. 1. Nature And Design Of This Work, lead paragraph

Source: Mathematical Thought from Ancient to Modern Times (1972), p. 346
Context: Fermat applied his method of tangents to many difficult problems. The method has the form of the now-standard method of differential calculus, though it begs entirely the difficult theory of limits.

Source: Lectures on The Industrial Revolution in England (1884), p. 29

Source: The Geological Evidences of the Antiquity of Man (1863), Ch.21, p. 410