1. Introduction. 2. The Argument. 3. IR Theory: A Critical Evaluation. 4. The Preferred Mode of Explanation: A Further Presentation. 5. Testing Theories. 6. Salient Environment and Domestic Explanatory Factors: The Nature of the Interplay. 7. Two Illustrations of Interplay. 8. The Role of International Organizations. 9. Theory and Reality of International Politics.