Self-criticism, cruel, unsparing criticism that goes to the very root of the evil, is life and breath for the proletarian movement.

History is the only true teacher, the revolution the best school for the proletariat.

Tomorrow the revolution will already 'raise itself with a rattle' and announce with fanfare, to your terror: I was, I am, I will be!

Only through the conscious action of the working masses in city and country can it be brought to life, only through the people's highest intellectual maturity and inexhaustible idealism can it be brought safely through all storms and find its way to port.

The most revolutionary thing one can do is always to proclaim loudly what is happening.

Tomorrow the revolution will 'rise up again, clashing its weapons,' and to your horror it will proclaim with trumpets blazing: I was, I am, I shall be!

[Geology] opens up such wide intellectual vistas and supplies a more perfectly unified and more comprehensive conception of nature than any other science.