Aleksandr Solzhenitsyn said this quote
“ That Marxism is not a science is entirely clear to intelligent people in the Soviet Union. One would even feel awkward to refer to it as a science. Leaving aside the exact sciences, such as physics, mathematics, and the natural sciences, even the social sciences can predict an event—when, in what way and how an event might occur. Communism has never made any such forecasts. It has never said where, when, and precisely what is going to happen. Nothing but declamations. Rhetoric to the effect that the world proletariat will overthrow the world bourgeoisie and the most happy and radiant society will then arise. ”