"As I grew older my lectures became simpler; I tried to say fewer things and to say them better, with more humanity. This book continues in a different way the same evolution, but it is not yet as simple as I would have liked to have made it."

“Erudition without pedantry is as a rare as wisdom itself.”

“A deed happens in a definite place at a definite time, but if it be sufficiently great and pregnant, its virtue radiates everywhere in time and space.”

“It is childish to assume that science began in Greece; the Greek "miracle" was prepared by millenia of work in Egypt, Mesopotamia and possibly in other regions. Greek science was less an invention than a revival.”

“The ability of nonintelligent people to understand the most complicated mechanisms and to use them has always been to me a cause of astonishment: their inability to understand simple questions is even more astonishing. The general acceptance of simple ideas is difficult and rare, and yet it is only when simple, fundamental, ideas have been accepted that further progress becomes possible on a higher level.”

“… science is the most revolutionary force in the world.”

“The scientific books written in Arabic durng the Middle Ages were, for a few centuries, the main vehicle of the living science.”