Leopold Infeld

"The scientist tries to understand the origin of our solar system, the structure of the universe and the laws governing the atom. He has discovered X rays, the radioactive substances, and he has built cyclotrons. He has foreseen the existence of electromagnetic and electronic waves. Out of his thought has grown the technique of our century. But not until today has he begun to notice that the earth on which he moves is covered with sweat and with blood and that in the world in which he lives "the son of man has nowhere to lay his head.""

"… mathematicians progress only by doubt, through humble and constant attempts to impinge on the immense domain of the unknown."