When the mind has become pure the chances of its being ruffled by external disturbances are greatly reduced. At such a stage the yogin takes a firm posture (_asana_) and fixes his mind on any object he chooses. It is, however, preferable that he should fix it on Is'vara, for in that case Is'vara being pleased removes many of the obstacles in his path, and it becomes easier for him to attain success. But of course he makes his own choice, and can choose anything he likes for the unifying concentration (_samadhi_) of his mind. There are four states of this unifying concentration namely _vitarka, vicara, ananda_ and _asmita_. Of these vitarka and vicara have each two varieties, _savitarka, nirvitarka, savicara, nirvicara_ [Footnote ref 395]. When the mind concentrates on objects, remembering their names and qualities, it is called the savitarka stage; when on the five tanmatras with a remembrance of their qualities it is called savicara, and when it is one with the tanmatras without any notion of their qualities it is called nirvicara. Higher than these are the ananda and the asmita states. In the ananda state the mind concentrates on the buddhi with its functions of the senses causing pleasure. In the asmita stage buddhi concentrates on pure substance as divested of all modifications. In all these stages there are objects on which the mind consciously concentrates, these are therefore called the _samprajnata_ (with knowledge of objects) types of samadhi. Next to this comes the last stage of samadhi called the _asamprajnata_ or nirodha samadhi, in which the mind is without any object. By remaininglong in this stage the old potencies (sa@mskaras) or impressions due to the continued experience of worldly events tending towards the objective world or towards any process of experiencing inner thinking are destroyed by the production of a strong habit of the nirodha state. At this stage dawns the true knowledge, when the buddhi becomes as pure as the puru@sa, and after that the citta not being able to bind the puru@sa any longer returns back to prak@rti.
In order to practise this concentration one has to see that there may be no disturbance, and the yogin should select a quiet place on a hill or in a forest. One of the main obstacles is, however, to be found in our constant respiratory action. This has to be stopped by the practice of _pra@nayama_. Pra@nayama consists in taking in breath, keeping it for a while and then giving it up. With practice one may retain breath steadily for hours, days, months and even years. When there is no need of taking in breath or giving it out, and it can be retained steady for a long time, one of the main obstacles is removed.
The process of practising concentration is begun by sitting in a steady posture, holding the breath by pra@nayama, excluding all other thoughts, and fixing the mind on any object (_dhara@na_). At first it is difficult to fix steadily on any object, and the same thought has to be repeated constantly in the mind, this is called _dhyana._ After sufficient practice in dhyana the mind attains the power of making itself steady; at this stage it becomes one with its object and there is no change or repetition. There is no consciousness of subject, object or thinking, but the mind becomes steady and one with the object of thought. This is called _samadhi_ [Footnote ref 396]. We have already described the six stages of samadhi. As the yogin acquires strength in one stage of samadhi, he passes on to a still higher stage and so on. As he progresses onwards he attains miraculous powers (_vibhuti_) and his faith and hope in the practice increase. Miraculous powers bring with them many temptations, but the yogin is firm of purpose and even though the position of Indra is offered to him he does not relax. His wisdom (_prajna_) also increases at each step. Prajna knowledge is as clear as perception, but while perception is limited tocertain gross things and certain gross qualities [Footnote ref 397] prajna has no such limitations, penetrating into the subtlest things, the tanmatras, the gu@nas, and perceiving clearly and vividly all their subtle conditions and qualities [Footnote ref 398]. As the potencies (_sa@mskara_) of the prajna wisdom grow in strength the potencies of ordinary knowledge are rooted out, and the yogin continues to remain always in his prajna wisdom. It is a peculiarity of this prajna that it leads a man towards liberation and cannot bind him to sa@msara. The final prajnas which lead to liberation are of seven kinds, namely, (1) I have known the world, the object of suffering and misery, I have nothing more to know of it. (2) The grounds and roots of sa@msara have been thoroughly uprooted, nothing more of it remains to be uprooted. (3) Removal has become a fact of direct cognition by inhibitive trance. (4) The means of knowledge in the shape of a discrimination of puru@sa from prak@rti has been understood. The other three are not psychological but are rather metaphysical processes associated with the situation. They are as follows: (5) The double purpose of buddhi experience and emancipation (_bhoga_ and _apavarga_) has been realized. (6) The strong gravitating tendency of the disintegrated gu@nas drives them into prak@rti like heavy stones dropped from high hill tops.
(7) The buddhi disintegrated into its constituents the gu@nas become merged in the prak@rti and remain there for ever. The puru@sa having passed beyond the bondage of the gu@nas shines forth in its pure intelligence. There is no bliss or happiness in this Sa@mkhya-Yoga mukti, for all feeling belongs to prak@rti. It is thus a state of pure intelligence. What the Sa@mkhya tries to achieve through knowledge, Yoga achieves through the perfected discipline of the will and psychological control of the mental states.