Inner Alchemy (Neidan): Merging with the Dao (煉虛合道)

Liàn Xū Hé Dào (煉虛合道) is the final stage of Neidan: emptiness (xū) and the Dao become indistinguishable, completing the alchemical return to the source. The Cantong Qi describes this as the elixir of immortality (jīndān) fully realized — not a substance but a state where the practitioner's being and the Dao's ceaseless movement are no longer separate. Yet the Neidan masters of the Quanzhen lineage insist this is not a permanent attainment but a continuous practice: because the Dao never ceases its transformations (huà), the sage who merges with it does not arrive at a final resting place but participates in perpetual change.