From Notes Of Class Talks And Lectures of Volume 6 of The Complete Works of Swami Vivekananda
Concentration is the essence of all knowledge; nothing can be done without it. Ninety per cent of thought force is wasted by the ordinary human being, and therefore he is constantly committing blunders; the trained man or mind never makes a mistake. When the mind is concentrated and turned backward on itself, all within us will be our servants, not our masters. The Greeks applied their concentration to the external world, and the result was perfection in art, literature, etc. The Hindu concentrated on the internal world, upon the unseen realms in the Self, and developed the science of Yoga. Yoga is controlling the senses, will and mind. The benefit of its study is that we learn to control instead of being controlled. Mind seems to be layer on layer. Our real goal is to cross all these intervening strata of our being and find God. The end and aim of Yoga is to realise God. To do this we must go beyond relative knowledge, go beyond the sense – world. The world is awake to the senses, the children of the Lord are asleep on that plane. The world is asleep to the Eternal, the children of the Lord are awake in that realm. These are the sons of God. There is but one way to control the senses — to see Him who is the Reality in the universe. Then and only then can we really conquer our senses.
Concentration is restraining the mind into smaller and smaller limits. There are eight processes for thus restraining the mind. The first is Yama, controlling the mind by avoiding externals. All morality is included in this. Beget no evil. Injure no living creature. If you injure nothing for twelve years, then even lions and tigers will go down before you. Practise truthfulness. Twelve years of absolute truthfulness in thought, word, and deed gives a man what he wills. Be chaste in thought, word, and action. Chastity is the basis of all religions. Personal purity is imperative. Next in Niyama, not allowing the mind to wander in any direction. Then Asana, posture. There are eighty – four postures: but the best is that most natural to each one; that is, which can be kept longest with the greatest ease.
After this comes Pranayama, restraint of breath. Then Pratyahara, drawing in of the organs from their objects. Then Dharana, concentration. Then Dhyana, contemplation or meditation. (This is the kernel of the Yoga system.) And last, Samadhi, superconsciousness. The purer the body and mind, the quicker the desired result will be obtained. You must be perfectly pure. Do not think of evil things, such thoughts will surely drag you down. If you are perfectly pure and practise faithfully, your mind can finally be made a searchlight of infinite power. There is no limit to its scope. But there must be constant practice and non – attachment to the world. When a man reaches the superconscious state, all feeling of body melts away. Then alone does he become free and immortal. To all external appearances, unconsciousness and superconsciousness are the same; but they differ as a lump of clay from a lump of gold. The one whose whole soul is given up to God has reached the superconscious plane.