Why did South Korea pursue selective engagement amid intensifying U.S.–China rivalry under Moon Jae-in (2017–2022), despite structural pressure to align with one great power in a system already characterized by concentrating multipolarity? Existing neoclassical realist explanations invoke domestic intervening variables but pay insufficient attention to how leaders perceive and interpret systemic pressures. Drawing on perceptual neoclassical realism (PNCR), this paper argues that leaders' perceptions constitute the principal transmission belt between structural constraints and foreign policy choice. Building on an ideology–threat perception model, it shows that Moon's progressive ideology shaped a comprehensive threat perception in which North Korea remained the primary threat despite active engagement, China functioned as a mixed-threat amplifier oscillating between partner and pressure source, and the United States served as a mixed-threat mitigator whose alliance demands carried entrapment risks. These perceptions produced selective engagement: issue-specific cooperation with both great powers rather than firm alignment with either.
