‘A theory of international relations needs to perform four principal tasks. It should describe, explain, predict, and prescribe’ (Kegley, 1995: 8).
This is a positivist statement. Especially the notion that a theory should be able to predict unmasks the positivist epistemology underpinning this statement. Only if one believes that we can identify causal relationships in an objective world along the lines of 'if A, then B', are predictions possible. If A occurs now in the present, we can then conclude that B will follow in the future with a great likelihood.