The Yoga Sutra states that samadhi is the ultimate tool of yoga. Note that this is not saying that samadhi is the ultimate goal of yoga. Where Samkhya practice involved discernment and renunciation, Classical Yoga involves samadhi and renunciation. But what is samadhi? That is not an easy question to answer.
Samadhi literally means “ecstasy.” It is acquired through devoted practice and grace. Practice alone will not guarantee samadhi. The grace of the guru (or of God) is also required. In samadhi, consciousness itself shines forth as the object of concentration. This means that, in samadhi, the subject and the object become one: consciousness senses, and is absorbed in, itself.
In the state of samadhi, all perceptions are shut off. Nothing disturbs the immersion of the self in the Self. Iyengar warns that in the state of samadhi, no action is possible as there is no one to act. We cannot do anything while in Samadhi; to do requires someone to do, and something to be done. The presence of a subject (the doer) and an object (the thing we are doing it to) causes us to leave this wondrous state of samadhi, and come back to being a player in life.
The Yoga Sutra, being a very technical manual, offers a hierarchy of levels of samadhi. In fact, all yoga traditions expound upon the various levels of samadhi that the yogi will pass through. It is beyond the scope of this journey to examine these stages. However, it is interesting to note that the Yoga Sutra and other sages warn that the danger to the yogi is greatest at this stage. Samadhi is so pleasurable that many seekers get stuck here; instead of pushing onward to the ultimate goal, they become sidetracked in this ecstatic state.
The ultimate goal is kaivalya: aloneness or aloofness.
Once a yogi has mastered samadhi and is back again in the ordinary world, what has changed? In samadhi there is no subject, no object, and consciousness is aware of only consciousness. When the yogi has left samadhi, she still knows the real nature of the universe. Once again she has entered the world of action, but now she acts out of the knowledge of the unity of everything. Iyengar says that kaivalya is samadhi in action. At this stage, the yogi is fully liberated. However, Iyengar is a modern yogin. The yogis of the classical era still believed in a dualist universe. Liberation is not possible while still trapped in the body. Kaivalya is not the final liberation. In modern times many scholars do interpret kaivalya to mean liberation, or moksha. Georg Feuerstein believes that, for the classical yogis, kaivalya meant only the ability to see without anything to be seen. This is the ultimate aloneness, but it is still one step removed from final liberation – the liberation that comes only with the release of the body.