In the second verse of the Tao Te Ching, Lao Tzu explains what happens when yin & yang separate from tai chi (non-duality). There are numerous methods for embodying this principle in oneself from traditional Taoist neigong (internal energy work) and meditation.

Cassandra Vieten at a presentation of the 129th Summer National Convention of the Theosophical Society in America explores what psychology can tell us about the soul and in what ways, if any, it can help us on the spiritual path. 2015.