If we knew the constituents of social, economic, and political systems and were successful in discovering and measuring their functional connections, we would have genuine knowledge of how the systems operate. Given the initial conditions, we would be able to predict the state of the system at any future time. Marxism-Leninism makes claim of having attained this kind of knowledge about social reality. Its predictive power with respect to social, economic, and political phenomena provides, therefore, a crucial test of the validity of this claim. If it is true, Marxism-Leninism as an applied science should be able to make predictions of the behaviour in some specified set of circumstances of various groups and of the outcome of complex social processes.