Capital is dead labour, which, vampire-like, lives only by sucking living labour, and lives the more, the more labour it sucks. - Karl Marx

Once the inner connection is grasped, all theoretical belief in the permanent necessity of existing conditions collapses before their collapse in practice — Letter to Ludwig Kugelmann (July 11, 1868)

It would be very difficult, if not altogether impossible, to establish any principle upon which the justice or expedience of capital punishment could be founded in a society glorying in its civilization.

Communism… is the genuine resolution of the antagonism between man and nature and between man and man; it is the true resolution of the conflict between existence and essence, objectification and self-affirmation, freedom and necessity, individual and species. It is the riddle of history solved and knows itself as the solution.