Is yoga union of body, mind and soul?
Yoga as a separate philosophical system has its root in Samkhya system of philosophy which has a very profound and detailed epistemology. Samkhya talks about the two ever present realities called Purusha and Prakriti i.e. consciousness and nature. Of these, nature is causal in essence however purusha is neither a cause nor an effect. As a spiritual identity we are Purusha (something entirely beyond the biological bodies and its functions). And physicality and mentality of our being has its origin from Prakriti (creation). Samkhya believes that since these two phenomena are ever present, there comes a state of confusion in the identities die to interaction between them. Purusha (pure consciousness) starts identifying itself with prakriti and since mind, intelligence and ego (identification with a particular body) are evolutes of prakriti, it starts influencing purusha. This according to the philosophers of samkhya and yoga is the basis of suffering or a start of a continuous cycle of pleasure and pain. And a way out of this suffering is to separate ourselves (purusha) from prakriti (mind and body). Samkhya philosophy is the main originator of these ideas which were taken along by yoga philosophy with very few differences. However samkhya lacks in the methodology which is given by yoga and this is known as Ashtanga yoga. An eight limbed path which gives practical way to reach a realization of the fact that we are spiritual beings and not just physical and mental. Patanjali (the philosopher of yoga discipline) has given a carefully drawn path to have the first hand experience of purusha with the practice of Ashtanga yoga that ultimately leads to a state called Samadhi where purusha or the self is not impacted by the prakriti. In this sense yoga is a path of separation of purusha from prakriti. Soul (purusha) has to be seen as a separate entity from body and mind (evolutes of prakriti) by the practice of 8 limbs of yoga. At salamba yoga teacher training school, India, these discussions are held as a part of philosophy discussions to better understand the epistemology of yoga discipline so that yoga is not just seen as a system of exercise however as a complete philosophical system.