A: Observation and Theory; 1: The Ontological Status of Theoretical Entities; 2: Observation; B: Theoretical Structure; 3: Empiricist Criteria Of Cognitive Significance: Problems and Changes; 4: Two Dogmas of Empiricism; 5: The Theoretician's Dilemma A Study in the Logic of Theory Construction; 6: What is a Scientific Theory?; 7: The Semantic Approach to Scientific Theories; C: Realism and Anti-Realism, Underdetermination; 8: To Save The Phenomena *; 9: How to Define Theoretical Terms; 10: Saving the Noumena *; 11: The Natural Ontological Attitude; 12: The Reality of Causes in a World of Instrumental Laws; 13: The Conventionalist Thesis and its First Critics; 14: The Framework of Philosophical Perplexity; 15: Realism and Reason; 16: On Empirically Equivalent Systems of the World