„Ich kann die Bewegungen der Himmelskörper berechnen, aber nicht die Verrücktheit der Menschen.“
Original
I can calculate the motions of the heavenly bodies, but not the madness of the people.
Such a statement is indicated as his response to a question regarding the financial fiasco known as the South Sea Bubble; the earliest mention of this famous anecdote appears to be from manuscripts of the Second Memorandum Book (1756) of Joseph Spence, first published in Anecdotes, Observations, and Characters, of Books and Men (1820) https://archive.org/details/anecdotesobserv00singgoog edited by in Samuel Weller Singer; a Lord Radnor is quoted as saying:
When Sir Isaac Newton was asked about the continuance of the rising of South Sea stock? — He answered, "that he could not calculate the madness of the people."
Variants:
I can calculate the motions of erratic bodies, but not the madness of a multitude.
As quoted in "Mammon and the Money Market", in The Church of England Quarterly Review (1850), p. 142 http://books.google.com/books?id=s_cDAAAAQAAJ&pg=PA142&dq=%22but+not+the+madness%22&hl=en&ei=nUtbTfuoCYG6ugPFi4n4DA&sa=X&oi=book_result&ct=book-preview-link&resnum=1&ved=0CCkQuwUwAA#v=onepage&q=%22but%20not%20the%20madness%22&f=false
I can calculate the motions of the heavenly bodies, but not the madness of people.
I can calculate the motions of heavenly bodies but not the madness of men.
I can calculate the movement of the stars, but not the madness of men.
Disputed
Isaac Newton 53
englischer Naturforscher und Verwaltungsbeamter 1643–1727Ähnliche Zitate

Pensées I, 33
Original franz.: "Les hommes sont si nécessairement fous, que ce serait être fou par un autre tour de folie de n'être pas fou."

„Schieß doch. Schieß! Es ist nur ein Mensch den du tötest aber nie eine ganze Bewegung.“