Yoga Sutras of Patanjali are simply amazing. I have no other words. It is not a philosophy but a science. The word yoga means union. It is a science of union. Achieved through discipline. The best discourse on the yoga sutras I have come across is by Osho. This was Osho at his peak, his finest.
All the discourses in audio files are available here:
http://www.oshoworld.com/discourses/audio_eng.asp?cat=Y
I am saddened with what has become of Yoga in the western world. It is not a power workout of postures and enjoying the fact you just sweated a bucket. Now you can drink that almond kale smoothie next and say namaste to good health. And yoga might seem like its only concerned with body postures - the asanas. But the path of yoga - starts with the outer, the body. Adds a discipline through the postures before you go higher to the inner, the mind. And finally to the union.
There are eight limbs of Yoga, or eight steps to achieve union, the Samadhi. Patanjali's yoga sutras state: Yam, Niyam, Asan, Pranayam, Pratyahar, Dharana, Dhyan and Samadhi
Yama - Self-restraint. Live consciously; related with people consciously.
Niyama - Fixed-observance. Life with regularity. Life with discipline.
Asana - Relaxed posture. Body in rest.
Pranayam - Breath regulation. Breathing techniques. Discover breathing rhythm.
Pratyahara - Sense withdrawal. Turning inward. Taking a break from sensory inputs.
Dharana - Focused concentration. Fix consciousness on a point.
Dhyan - Dropping the object of meditation. Pure contemplation. Meditative absorption
Samadhi - Union. Enlightenment.
Osho explains very beautifully: Yam is the bridge between you and others - live consciously; relate with people consciously. Then the second two, Niyam and Asan - they are concerned with your body. Third, Pranayam is again a bridge. As the first, Yam, is a bridge between you and others, the second two are a preparation for another bridge - your body is made ready through Niyam and Asan -- then Pranayam is the bridge between the body and the mind. Then Pratyahar and Dharana are the preparation of the mind. Dhyan again, is a bridge between the mind and the soul. And Samadhi is the attainment. They are interlinked, a chain; and this is your whole life.
My master adds that these eight steps do not have to be rungs of ladder, they are can be done simultaneously. And one waits for the eighth. But performs the seven other to create the conditions for the eighth.
From intellect to action. From knowledge to experience. And finally from learning to unlearning. Back to the beginning. Back to the union.
Not the body, not the mind, simply consciousness - the purusha.
The path of a Yogi. Om.