Religion is the opium of the masses. – Karl Marx
The product of mental labor – science – always stands far below its value, because the labor-time necessary to reproduce it has no relation at all to the labor-time required for its original production. – Karl Marx
Natural science will in time incorporate into itself the science of man, just as the science of man will incorporate into itself natural science: there will be one science. – Karl Marx
The ideas of the ruling class are in every epoch the ruling ideas, i.e., the class which is the ruling material force of society, is at the same time its ruling intellectual force. – Karl Marx