Scientifically, evolution is defined as the process where more refined life forms (vehicles of consciousness) grow and develop from the less refined. That is, more advanced life forms arise from lower forms, the gross produces the subtle. This is the theory of scientific evolution. Tantra and Indian thought in general has a completely different concept of evolution. Tantra regards the refinement of life forms (that is, scientific evolution) as merely the pattern of the manifested world. It is the blueprint, the design. It is not the source of life as we know it. The real meaning of evolution, written about by Indian sages thousands of years before Darwin, is the process of Shakti arising or evolving out of Shiva, of the material evolving out of the immaterial. That is, in a deeper sense, each and every life form is not the result of the unfoldment of previous life forms, every form of life has evolved from the underlying source of existence called consciousness.The subtle does not evolve from the gross (scientific evolution) but the gross evolves out of the subtle (spiritual evolution). Consider a movie film. It has a story that unfolds from the beginning to the end; this can be compared to scientific evolution. Each scene is related to the next but at the same time the story in the film is not the source of the pictures. The source of the picture is elsewhere, namely on the film strip. The film strip can be compared, though grossly, to consciousness. It is a projection of the film on to the screen from the film strip that tantra and other Indian systems regard as evolution, not the flow of the story itself.
This evolution (in the tantric sense) or manifestation of the material world, including life, is in two directions: the outward and the inward. In the outward direction (termed pravritti) Shakti plunges downwards and produces the world of forms. In the inward direction (termed nivritti) Shakti moves in the opposite direction from the gross to the more subtle. The further Shakti moves outwards and downwards, the deeper is the veil of ignorance. The greater the inward and upward movement of Shakti, the greater the awareness, the knowledge or the grace (anugraha) of divinity.
There is an exact parallel concept in Taoism. Shakti is known as Teh which is divided intoyin (nivritti) andyang (pravritti). Yin is the tendency to return to the source, to withdraw and concentrate itself and merge itself with the substratum of consciousness. Yang is expansion, action and creation of all things. These are two rhythms – the yang or action and going forth, of flowering potential; and yin is the retracing, the return to the centre.
The aim of tantric practice is to reverse the downward and outward movement of Shakti and retrace one’s steps along the inward and upward path to higher awareness. The aim is to reverse the direction of evolution and return to the source: to reunite Shakti with Shiva.
Tantra divides people into two basic groups:
1. Those who follow the pravritti path, the path of extroversion, the path of the world, of activity and of sensual enjoyment.
2. Those who follow the nivritti path, the path for those who want to return to their source and know their real self.
Most people are ideally suited to the pravritti path. Tantra caters for both groups of people and prescribes special practices for each group. The path to enlightenment is first of all to follow the path of pravritti: to exhaust and fulfil all interest in the things of the world. In this manner one will progress naturally to the nivritti path. No force or effort will be required – it will arise spontaneously. It is the nivritti path that eventually leads to experience of the infinite. But most people are not ready for the nivritti path and must first of all tread the pravritti path and enjoy life in all its facets to the full. The practices of tantra are designed to lead the individual smoothly through both paths to the supreme experience. Tantra recommends those practices that are most suitable for the personality and stage of development of the individual. It realizes clearly that there is no point in forcing the path of introspection ‘down the throats’ of people who are not ready or who are completely disinclined towards it. Such is the depth of understanding and breadth of tantra. Its aim is to lead everyone to enlightenment but in a natural manner that does not build up complexes and do more harm than good.