"Until he was 40, Hobbes was a talented scholar exhibiting modest originality. Versed in the humanities, he was dissatisfied with his erudition, and had little exposure to the exciting new breakthroughs achieved by Galileo, Kepler and other scientists who were then revolutionizing the scholarly world.
One day, in a library, Hobbes saw a display copy of Euclid's Elements opened to Book I Proposition 47, Pythagoras's theorem. He was so astounded by what he read that he used a profanity that his first biographer, John Aubrey, refused to spell out: " 'By G__' Hobbes swore, 'this is impossible!'." He read on, intrigued. The demonstration referred him to other propositions, and he was soon convinced that the startling theorem was true.
Hobbes was transformed. He began obsessively drawing figures and writing calculations on bed sheets and even on his thigh. His approach to scholarship changed. He began to chastise philosophers of the day for their lack of rigour and for being unduly impressed by their forebearers. Hobbes compared other philosophers unfavourably with mathematicians, who proceeded slowly but surely from "low and humble principles" that everyone understood.
In books such as Leviathan, Hobbes reconstructed political philosophy by establishing clear definitions of terms, then working out implications in an orderly fashion. Pythagoras's theorem had taught him a new way to reason and to present persuasively its fruits."
Read the whole thing here.