ZHU Xi established a unique theoretical system for the guqin based on his philosophical foundation of the Li-Qi theory. Within the dualistic framework of Li (Principle) and Qi (Vital Force), he interconnected the instrument, its tuning system, and the laws of nature, transforming the guqin into a medium embodying the Heavenly Principle. Regarding aesthetic orientation, he opposed the Song guqin circle's trend of pursuing intricate techniques, advocating instead for a return to the serene and untrammeled style and emphasizing the “natural” expression of the pentatonic framework. On the practical level, ZHU Xi integrated guqin artistry with Neo-Confucian self-cultivation by employing the disciplined practice of “maintaining reverence and preserving stillness” in playing to nurture moral character, while exploring the Heavenly Principle (Li) through the “investigation of things and extension of knowledge” via qin tuning systems, ultimately achieving the self-cultivation goal of “nourishing a harmonious nature and restraining resentful desires.”