“Combinatory play seems to be the essential feature in productive thought.”

“Wisdom is not a product of schooling but of the lifelong attempt to acquire it.”

“The really valuable thing in the pageant of human life seems to me not the political state, but the creative, sentient individual, the personality; it alone creates the noble and the sublime, while the herd as such remains dull in thought and dull in feeling.”

“The formulation of the problem is often more essential than its solution, which may be merely a matter of mathematical or experimental skill.”

“Play is the highest form of research.”

“God does not play dice with the universe.”

“Knowledge exists in two forms - lifeless, stored in books, and alive, in the consciousness of men. The second form of existence is after all the essential one; the first, indispensable as it may be, occupies only an inferior position.”