The word Yoga comes from the Sanskrit word "Yuj" meaning to yoke, join or unite. This implies joining or integrating all aspects of the individual - body with mind and mind with soul - to achieve a happy, balanced and useful life, and spiritually, uniting the individual with the supreme.
In India, Yoga is considered one of the six branches of classical philosophy and is referred to throughout the Vedas - ancient Indian scriptures and amongst the oldest texts in existence.The Upanishads are also broadly philosophical treatises which postdate the Vedas and deal with the nature of the "soul" and universe.
However, the origins of yoga are believed to be much older than that, stemming from the oral traditions of Yogis, where knowledge of Yoga was handed down from Guru (spiritual teacher) to Sisya (spiritual student) all the way back to the originators of Yoga, "the Rishis," who first began investigation into the nature of reality and man's inner world.
Legend has it that knowledge of Yoga was first passed by Lord Shiva to his wife Parvati and from there into the lives of men.
According to the Yoga Sutras of Patanjali, the ultimate aim of Yoga is to reach "Kaivalya" (emancipation or ultimate freedom). This is the experience of one's innermost being or "soul" (the Purusa). Then one becomes free of chains of cause and effect (Karma) which tie us to continual reincarnation. In Kaivalya one is said to exist in peace and tranquillity, having attained absolute knowledge of the difference between the spiritual which is timeless, unchanging and free of sorrows, and the material which is not.
This is considered desirable as life is analysed as ultimately full of sorrows and pain- even pleasure and joy leave pain and loss when they have gone as nothing in the material world is permanent.
Yoga is therefore a spiritual quest. However, along the path of yoga, the aspirant also gains health, happiness, tranquillity and knowledge which are indicators of progress and an encouragement to continue their practice. Buddhism and other Eastern spiritual traditions use many techniques derived from Yoga.
There are said to be 4 main paths (Margas), according to the Bhagavad Gita, by which to reach the ultimate goal of Yoga - "Kaivalya." There is the path of Knowledge (Jnana Marga) in which one learns to discriminate between what is real and what is illusory, the path of selfless work (Karma marga), the path of devotion (Bhakti Marga) and the path of control of the mind (Yoga Marga) where all the activities of the mind and consciousness are studied and brought under control. From these have come the various paths of yoga which can be followed.
It must be realised that there are no clear cut boundaries between these various paths and all draw on the practices and philosophy of the others; effectively all paths have the same goal and "tread the same terrain." They are different views of the same topic.
Various schools or styles of Yoga have grown around each of these paths, which emphasise different aspects of these paths, or a combination of them, in their practical methodology. Usually these schools are established by renowned teachers or gurus and reflect their methodologies and ways of practicing, teaching and following the path of yoga. Some of the most well known modern schools or styles of yoga include: Iyengar, Astanga, Vini, Ananda, Anusara, Bikram, Integral, Kali Ray Tri, Kripalu, Kundalini and Sivananda. (See this article for a brief explanation of the differences between some of these schools at a practical level in terms of how classes are run.) Interestingly, 3 of the most popular schools today - Iyengar, Astanga and Vini Yoga - were all developed by students of Sri T. Krishnamacharya.
Particular styles or methods may be considered more effective than others or may suit an individual's temperament better. That said, it must always be remembered that all these are merely different methods of reaching for the same ultimate goal. They are all aspects of the overall philosophy of Yoga.
The philosophy of Yoga comes from many sources and has been presented in many fashions with differing emphasis depending on the understanding of the author.
The Vedas and Upanishads give some of the earliest references to the paths of yoga. These scriptures form the basis of Indian religious practices but contain many varied references to yoga and other things.
There are the Puranas, also ancient, which deal with the nature of the universe.
Famous epics such as the Ramayana and Mahabarata contain stories of the gods and lectures on moral and philosophical subjects with references to yogis and yogic practices.
The Bhaghavad Gita is a particularly famous part of the Mahabarata which contains a detailed discourse on yoga by Krisna to Arjuna.
Other texts such as the Hatha Yoga Pradipika are more "technical manuals" of yoga which go into detail on technique as opposed to just the theory.
In general all these texts discuss Yoga from the particular standpoint of the authors and the paths to Yoga they have followed. In many ways this subject can be confusing for lack of a clear overview. This need is answered in the Yoga Sutras of Patanjali.
The varied philosophies and methodologies of Yoga itself were clearly and methodically brought together and presented by the sage Patanjali in his set of 196 aphorisms called "The Yoga Sutras," written some 2200 years ago. The Sutras bring together all the various strands of theory and practice from all sources of yoga and present them in one concise, integrated and comprehensive text. How all the aspects interrelate and form part of the whole body of yoga are clearly elucidated. There are 8 disciplines to yoga as presented by Patanjali (thus Astanga yoga - 8 limbed yoga) which must be practiced and refined in order to perceive the true self- the ultimate goal of Yoga:
The key elements of all the paths of yoga are presented in a balanced perspective and legend has it that Patanjali was himself a realised being and so writing from experience.
In the four chapters of his sutras he explains the levels of higher consciousness (Samadhi) which the aspirant must experience before reaching Kaivalya (emancipation) and the end of this world's spiritual pursuit. The second chapter deals with the methodology which must be followed to reach Samadhi and the hindrances which may be encountered. The unusual powers that may develop are also described with the warning that their lure must be avoided, while the final chapter covers the achievement of Kaivalya in detail.
These Sutras were and are still considered a most profound and enlightening study of the human psyche. Patanjali shows how through the practice of Yoga, we can transform ourselves, gain mastery over the mind and emotions, overcome obstacles to our spiritual evolution and attain the goal of yoga: liberation from the bondage of worldly desires. Written in Sanskrit, many commentaries and translations have been written over the centuries by various scholars and practitioners; each interpreting as per their era and understanding.
BKS Iyengar is one amongst several contemporary authors, having completed Light on the Yoga Sutras of Patanjali in the light of his own hard practice and experience, but using modern day language and concepts.