IV:1-3 Adeptship is achieved by purification of man's three bodies. It is also attainable through the grace of the guru. Purification comes through Nature, penance, and mantras. Through Nature there is purification of dense matter (the physical body); through penance, purification of the fine matter (the subtle body); through mantras, purification of the mind.
IV:4-5 Through the holy effect of the mantra, the Pranava or Aum sound becomes audible. The sacred sound is heard in various ways, according to the devotee's stage of advancement (in purifying his heart).
IV:6 One who cultivates the heart's natural love obtains the guidance of a guru, and starts his sadhana (path of spiritual discipline). He becomes a Pravartaka, an initiate.
IV:7 By the practice of Yama and Niyama, the eight meannesses of the human heart disappear and virtue arises. Man thus becomes a Sadhaka, a true disciple, fit to attain salvation.
IV:8 He progresses in godliness, hears the holy Aum sound, and becomes a Siddha, divine personage.
IV:9 Then he perceives the manifestations of Spirit, and passes through the seven Patala Lokas (or centers in the spine), beholding the seven rishis.
IV:10 Then, because of yoga knowledge and power, man obtains supremacy over the seven Swargas (heavens). He achieves salvation by dissolving the four original ideas (the "four manus" or primal thoughts by which creation sprang into being).
IV:11 Being thus victorious over the powers of Darkness and Ignorance, man becomes one with God.
IV:12 Knowledge of evolution, life, and dissolution thus leads to complete emancipation from the bonds of Maya, delusion. Beholding the self in the Supreme Self, man gains eternal freedom.