The point of departure of Yoga meditation is concentration on a single object; whether this is a physical object (the space between the eyebrows, the tip of the nose, something luminous, etc.), or a thought (a metaphysical truth), or God (Ishvara) makes no difference. This determined- and continuous concentration, called ekagrata ('on a single point'), is obtained by integrating the psychomental flux (sarvarthata, 'variously directed, discontinuous, diffused attention'). This is precisely the definition of yogic technique: yogah cittavritti-nirodhyah, i.e., the yoga is the suppression of psychomental states (Yoga-sutras, 1, 2).
The immediate result of ekagrata, concentration on a single point, is prompt and lucid censorship of all the distractions and automatisms that dominate -or, properly speaking, compose-profane consciousness. Completely at the mercy of associations (themselves produced by sensations and the vasanas), man passes his days allowing himself to be swept hither and thither by an infinity of disparate moments that are, as it were, external to himself. The senses or the subconscious continually introduce into consciousness objects that dominate and change it, according to their form and intensity. Associations disperse consciousness, passions do it violence, the 'thirst for life' betrays it by projecting it outward. Even in his intellectual efforts, man is passive, for the fate of secular thoughts (controlled not by ekagrata but only by fluctuating moments of concentration, kshiptavikshiptas) is to be thought by objects. Under the appearance of thought, there is really an indefinite and disordered flickering, fed by sensations words, and memory. The first duty of the yogin is to think-that is, not to let himself think. This is why Yoga practice begins with ekagrata, which darns the mental stream and thus constitutes a 'psychic mass,' a solid and unified continuum.
The practice of ekagrata tends to control the two generators of mental fluidity: sense activity
(indriya) and the activity of the subconscious (samskara). Control is the ability to intervene, at will
and directly, in the functioning of these two sources of mental 'whirlwinds' (cittavritti). A yogin can
obtain discontinuity of consciousness at will; in other words, he can, at any time and any place,
bring about concentration of his attention on a 'single point' and become insensible to any other
sensory or mnemonic stimulus. Through ekagrata one gains a genuine will-that is, the power freely
to regulate an important sector of biomental activity. It goes without saying that ekagrata can be
obtained only through the practice of numerous exercises and techniques, in which physiology plays
a role of primary importance. One cannot obtain ekagrata if, for example, the body is in a tiring or
even uncomfortable posture, or if the respiration is disorganized, unrhythmical. This is why,
according to Patanjali, yogic technique implies several categories of physiological practices and
spiritual exercises (called angas, 'members'), which one must have learned if one seeks to obtain
ekagrata and, ultimately, the highest concentration, samadhi. These 'members' of Yoga can be
regarded both as forming a group of techniques and as being stages of the mental ascetic itinerary
whose end is final liberation. They are: (1) restraints (yama), (2) disciplines (niyama), (3) bodily
attitudes and postures (asana); (4) rhythm of respiration (pranayama); (5) emancipation of sensory
activity from the domination of exterior objects (pratyahara); (6) concentration (dharana), (7) yogic
meditation (dhyana), (8) samadhi (Yoga-sutras, 11, 29).
Each class (anga) of practices and disciplines has a definite purpose. Patanjali hierarchizes these 'members of Yoga' in such a way that the yogin cannot omit any of them, except in certain cases. The first two groups, yama and niyama, obviously constitute the necessary preliminaries for any. type of asceticism, hence there is nothing specifically yogic in them. The restraints (yatna) purify from certain sins that all systems of morality disapprove but that social life tolerates. Now, the moral law can no longer be infringed here-as it is in secular life without immediate danger to the seeker for deliverance. In Yoga, every sin produces its consequences immediately. The five restraints are ahimsa, 'not to kill,' satya, 'not to lie,' asteya, 'not to steal,' brahmacarya, 'sexual abstinence,' aparigraha, 'not to be avaricious.'
Together with these restraints, the yogin must practise the niyamas --that is, a series of bodily and psychic 'disciplines.' 'Cleanliness, serenity "samtosha," asceticism "tapas," the study of Yoga metaphysics, and the effort to make God "Ishvara," the motive of all one's actions constitute the disciplines.' (Y.S., II, 32.)