Everyone goes through four stages of development in life. The first is childhood: you are not mature, you are learning to use your senses and faculties; your thoughts and decisions are erratic, there is no control in these formative years of life. Then, when you gain experience and education, your thoughts and ideas change. What you used to believe in at the age of sixteen does not hold true at the age of forty. The whole mindset undergoes a change; the freedom of childhood is replaced by responsibilities of adulthood. With the responsibilities, the behaviour, the thinking, the expression, everything changes. That is the second stage of life: adulthood.
The third stage is old age. After retirement, when there is no further involvement with society or family, again the personality undergoes a change. Until retirement you are dynamic and active; after retirement suddenly you have nothing to do. People who used to salute you don't even offer you a seat to sit on anymore. The mindset has to change and be given a new direction. Finally, the faculties that helped you grow in life begin to shut down.
Formation is the first and shutting down is the last; in between is professional responsibility and the retired mind: the active mind and the retired mind. These are the four yugas of life. Similarly, the four yugas of earth, Satya, Treta, Dwapara and Kali, represent the childhood, the adulthood, the old age and the final condition of the decaying body. These are the four great changes. The pattern of living, thinking, interacting, eating, playing, enjoying, everything changes in each stage.
Pashupata yoga was prevalent in Satya Yuga. At that time, it was practised by the sages, seers, people who would perform austerities, live in isolation and perfect their own spiritual sadhanas. This included exponents like Dattatreya, Agastya, Bhrigu, who are considered demigods in the Indian mythology. They had that level of perfection and mastery over their body, mind and the elements, therefore they were given a higher status. Their entire focus in life was to experience the Shiva nature by transcending the fetters and bondages of mind.
In the second period, Treta Yuga, the period of Rama, the rishis brought the concept of meditation to human society. People in society did not practise the full yoga; that was left only to the recluse group. They practised meditation, mantras and other things that could be done in the household environment to improve the quality of life. Thus, at that time Pashupata yoga came out of the rishis’ ashrams into certain homes in society. That was the first introduction. Thereafter the social movement gained momentum and people started to practise mantras, meditations, some asanas and other techniques contained in the Pashupata yoga. At that time, yoga was seen in five parts.
The first was mantra yoga, which was the first yoga to be introduced to society during Rama’s time, along with meditation. The first rules and disciplines of the practices were created. The first yama and niyama were introduced. The first yama was an idea put into the minds of people who were suffering: don’t think of suffering but be happy. As mentioned, when a sick person came to the ashram, Sri Swamiji used to say that the first thing you need to do is to forget that you are sick and feel that you are healthy. All this time you have been thinking, ‘I am sick, I am sick, I am sick.’ You have been saying to the doctors, “I have this problem, I have that problem.” You are living in the state of sickness all the time. When you come to the ashram, forget that you are sick, visualize yourself as a healthy person, walk like a healthy person, run like a healthy person, not like an invalid or sick person. Counter that effect of sickness and disease by cultivating the awareness of health. Similarly, when people are suffering mentally, you have to tell them to try and be happy. To come out of that dark mental state, one has to try to forget the pain and suffering and be happy. Therefore, happiness became the first yama and japa became the first niyama.
For the yogis, japa was an ongoing practice. In samadhi and meditation, they would be doing their japa, the mental repetition of the mantra. In society, the purpose of introducing mantra and japa was to give an opportunity to disconnect from the world for ten minutes. You are connected with the outside world all the time, your antennae are pointing out, picking up all the transmissions from the world. All your five antennae are always active, even at night when you sleep. Japa is the only time when you consciously say, ‘I am disconnecting myself and doing this practice. I am disconnecting myself from my condition, my feelings, my thoughts, my emotions, my pratyayas, conditionings, and I am focusing on mantra, japa and meditation.’ Japa gives one the ability to disconnect from the outer world, therefore it became the first niyama.
Then came the time of Krishna. By this time many other generation changes had also taken place. Mantra yoga was introduced in Rama’s time, and in Krishna’s time, four yogas came into existence: sparsha yoga, bhava yoga, abhava yoga and maha yoga. The mindset in Krishna’s time was different from the mindset in Rama’s time. In Krishna’s time, of Dwapara Yuga, the adulthood, sparsha yoga, bhava yoga, abhava yoga and maha yoga were introduced. All these yogas were integrated practices. They had asana, pranayama, mudra, bandha, pratyahara, dharana, everything on one big plate. They were not classified or separated.
Then came a time of crisis after Krishna: the civil war, and all the yogas receded into the background. Nevertheless, some rishis still remained active in their practice and experience of yoga in isolated pockets. These people classified yoga at that time, during the beginning of Kali Yuga. They were the likes of Patanjali, Narada, Shandilya, and many other sages. From mantra yoga the whole science of mantra was developed. From sparsha yoga emerged hatha yoga and its theories and practices. From bhava yoga came bhakti yoga. From abhava yoga came laya yoga. From maha yoga came lifestyle and jnana yoga. Other yogas also developed from the main group of practices, such as kriya and kundalini. The classical texts that we follow today belong to this period.