We all walk in mysteries. We are surrounded by an atmosphere about which we still know nothing at all.

Error is acceptable as long as we are young; but one must not drag it along into old age.

If everyone sweeps before his own front door, then the street is clean.

Everyone believes in his youth that the world really began with him, and that all merely exists for his sake.

Only he who finds empiricism irksome is driven to method.

All ages have said and repeated that one should strive to know one's self. This is a strange demand which no one up to now has measured up to and, strictly considered, no one should. With all their study and effort, people are directed to what is outside, to the world about them, and they are kept busy coming to know this and to master it to the extent that their purposes require. . . . How can you come to know yourself? Never by thinking, always by doing. Try to do your duty, and you'll know right away what you amount to. And what is your duty? Whatever the day calls for.

We are so constituted that we believe the most incredible things; and, once they are engraved upon the memory, woe to him who would endeavor to erase them.