It has been said that buddhi and the internal objects have evolved in order to giving scope to the experience of the puru@sa. What is the process of this experience? Sa@mkhya (as explained by Vacaspati) holds that through the senses the buddhi comes into touch with external objects. At the first moment of this touch there is an indeterminate consciousness in which the particulars of the thing cannot be noticed. This is called _nirvikalpa pratyak@sa_ (indeterminate perception). At the next moment by the function of the _sa@mkalpa_ (synthesis) and _vikalpa_ (abstraction or imagination) of manas (mind-organ) the thing is perceived in all its determinate character; the manas differentiates, integrates, and associates the sense-data received through the senses, and thus generates the determinate perception, which when intelligized by the puru@sa and associated with it becomes interpreted as the experience of the person. The action of the senses, ahamkara, and buddhi, may take place sometimes successively and at other times as in cases of sudden fear simultaneously. Vijnana Bhik@su differs from this view of Vacaspati, and denies the synthetic activity of the mind-organ (manas), and says that the buddhi directly comes into touch with the objects through the senses. At the first moment of touch the perception is indeterminate, but at the second moment it becomes clear and determinate [Footnote ref 384]. It is evident that on this view the importance of manas is reduced to a minimum and it is regarded as being only the faculty of desire, doubt and imagination.
Buddhi, including ahamkara and the senses, often called _citta_ in Yoga, is always incessantly suffering changes like the flame of a lamp, it is made up of a large preponderance of the pure sattva substances, and is constantly moulding itself from one content to another. These images by the dual reflection of buddhi and puru@sa are constantly becoming conscious, and are being interpreted as the experiences of a person. The existence of the puru@sa is to be postulated for explaining the illumination of consciousness and for explaining experience and moral endeavour. The buddhi is spread all over the body, as it were, for it is by its functions that the life of the body is kept up; for the Sa@mkhya does not admit any separate prana vayu (vital breath) to keep the body living. What are called _vayus_ (bio-motor force) in Vedanta are but the different modes of operation of this category of buddhi, which acts all through the body and by its diverse movements performs the life-functions and sense-functions of the body.
Apart from the perceptions and the life-functions, buddhi, or rather citta as Yoga describes it, contains within it the root impressions (_sa@mskaras_) and the tastes and instincts or tendencies of all past lives (_vasana_) [Footnote ref 385]. These sa@mskaras are revived under suitable associations. Every man had had infinite numbers of births in their past lives as man and as some animal. In all these lives the same citta was always following him. The citta has thus collected within itself the instincts and tendencies of all those different animal lives. It is knotted with these vasanas like a net. If a man passes into a dog life by rebirth, the vasanas of a dog life, which the man must have had in some of his previous infinite number of births, are revived, and the man's tendencies become like those of a dog. He forgets the experiences of his previous life and becomes attached to enjoyment in the manner of a dog. It is by the revival of the vasana suitable to each particular birth that there cannot be any collision such as might have occurred if the instincts and tendencies of a previous dog-life were active when any one was born as man.
The sa@mskaras represent the root impressions by which any habit of life that man has lived through, or any pleasure in which he took delight for some time, or any passions which wereengrossing to him, tend to be revived, for though these might not now be experienced, yet the fact that they were experienced before has so moulded and given shape to the citta that the citta will try to reproduce them by its own nature even without any such effort on our part. To safeguard against the revival of any undesirable idea or tendency it is therefore necessary that its roots as already left in the citta in the form of sa@mskaras should be eradicated completely by the formation of the habit of a contrary tendency, which if made sufficiently strong will by its own sa@mskara naturally stop the revival of the previous undesirable sa@mskaras.
Apart from these the citta possesses volitional activity (ce@s@ta) by which the conative senses are brought into relation to their objects. There is also the reserved potent power (s'akti) of citta, by which it can restrain itself and change its courses or continue to persist in any one direction. These characteristics are involved in the very essence of citta, and form the groundwork of the Yoga method of practice, which consists in steadying a particular state of mind to the exclusion of others.
Merit or demerit (_pu@nya, papa_) also is imbedded in the citta as its tendencies, regulating the mode of its movements, and giving pleasures and pains in accordance with it.