Prerequisites for yoga
“Knowledge (Jnana) does not come about from practice of yoga methods alone. Perfection in knowledge is in fact only for those who begin by practice of virtue (dharma). Yet, without yoga as a means, knowledge does not come about. The practice of yogic methods is not the means by itself, yet it is only out of that practice of yoga that the perfection in knowledge comes about. And so it is said by the teachers: ‘Yoga is for the purpose of knowledge of truth'” Thus wrote Shankara.
All things rest upon something else-that is, all things are supported by another. This is because a foundation is needed for anything to exist. Being Himself the Ultimate Support of all things, God alone is free from this necessity. Yoga, then, also requires support. As Trevor Leggett says in his introduction to Shankara’s commentary on the Yoga Sutras: “This is yoga presented for the man of the world, who must first clear, and then steady, his mind against the fury of illusory passions, and free his life from entanglements.” Patanjali very carefully and fully outlines the elements of the support needed by...