… if constructing the future and settling everything for all times are not our affair, it is all the more clear what we have to accomplish at present: I am referring to ruthless criticism of all that exists, ruthless both in the sense of not being afraid of the results it arrives at and in the sense of being just as little afraid of conflict with the powers that be.
– Karl Marx (1843)
The weapon of criticism cannot, of course, replace criticism of the weapon, material force must be overthrown by material force; but theory also becomes a material force as soon as it has gripped the masses. Theory is capable of gripping the masses as soon as it demonstrates ad hominem, and it demonstrates ad hominem as soon as it becomes radical. To be radical is to grasp the root of the matter. But, for man, the root is man himself.
-Karl Marx (1843)
[The declining rate of profit] is in every respect the most important law of modern political economy, and the most essential for understanding the most difficult relations. It is the most important law from the historical standpoint.
-Karl Marx (1857)
Our concern cannot simply be to modify private property, but to abolish it, not to hush up class antagonism but to abolish classes, not to improve the existing society but to found a new one.
-Karl Marx & Frederick Engels (1850)
He who pronounces himself in favour of the method of legal reforms in place of and as opposed to the conquest of political power and social revolution does not really choose a more tranquil, surer and slower road to the same goal. He chooses a different goal. Instead of taking a stand for the establishment of a new social order, he takes a stand for surface modifications of the old order.
-Rosa Luxemburg (1900)
The epoch of imperialism cannot permit the existence, in a single party, of the revolutionary proletariat’s vanguard and the semi-petty-bourgeois aristocracy of the working class.
-Vladimir I. Lenin (1915)
The world political situation as a whole is chiefly characterized by a historical crisis of the leadership of the proletariat.
-Leon Trotsky (1938)