Qi is usually translated as breath, vapour or energy and none of these is right, because the word does not sit on either side of a matter–spirit divide that Chinese thought never drew. Everything is qi at some degree of condensation: stone is dense and slow, thought is thin and quick, and a body is a temporary configuration that will disperse. This single-substance assumption is why the disciplines Westerners separate are not separate here — Chinese medicine, breathing practice, martial arts, geomancy, meditation and temple liturgy are all operations on qi, using a shared vocabulary of stagnation, depletion, excess and flow. It also explains why becoming immortal could be conceived as a physical engineering problem rather than a spiritual one: if the body is qi and qi can be refined, then in principle the body can be refined until it stops dispersing.