"No former age was ever in such a favorable position with regard to the sources of our knowledge of human nature. Psychology, ethnology, anthropology, and history have amassed an astonishingly rich and constantly increasing body of facts. Our technical instruments for observation and experimentation have been immensely improved, and our analyses have become sharper and more penetrating. We appear, nevertheless, not yet to have found a method for the mastery and organization of this material.... Unless we succeed in finding a clue of Ariadne to lead us out of this labyrinth, we can have no real insight into the general character of human culture; we shall remain lost in a mass of disconnected and disintegrated data which seem to lack all conceptual unity."

"Nevertheless. among all the temptations I will have to resist today. There would be the temptation of memory: to recount what was for me. and for those of my generation who shared it during a whole li…"

"With regard to the duration of human life, there does not appear to have existed from the earliest ages of the world to the present moment the smallest permanent symptom or indication of increasing pr…"

"There is no direct observational evidence for the curvature , the only directly observed data being the mean density and the expansion, which latter proves that the actual universe corresponds to the …"

"Three revolutions mark the history of life on earth. The first was the origin of life itself... The second... was the origin of multicellular organisms... The origin of human consciousness... was the …"