The wonder is, not that the field of stars is so vast, but that man has measured it

To accomplish great things we must not only act, but also dream; not only plan, but also believe.

(From an introductory speech at a session of the Académie Française, December 24, 1896)

The fool doth think he is wise, but the wise man knows himself a fool.

The greatest virtue of man is perhaps curiosity.

Devout believers are safeguarded in a high degree against the risk of certain neurotic illnesses; their acceptance of the universal neurosis spares them the task of constructing a personal one.

He flattered himself on being a man without any prejudices; and this pretension itself is a very great prejudice