In Hinduism, a study of the mind was not undertaken for its own sake. It used to be part of a philosophy primarily concerned with the attainment of emancipation. In Yoga psychology, the mind was considered interesting only insofar as it was means to liberation or self realization. Mind is said to have three components which perform three interrelated functions. The main component is buddhi. It is the organ of perception, understanding, deciding, ordering, storing, recalling, and having emotions, passions, and all mental faculties. Manas is the component which connects it with the body and the external world. Ahamkara is the third component which provides the ego-feeling or the awareness of one’s own existence.
Patanjali looks upon mind as an organ which continues to be associated with the self from birth to birth, carrying the traces of experiences from all past lives. It exists,not for its own sake, but for the sake of the self (IV. 24). Out of the vast storehouse of samskaras, only those which are related to the present birth would be revived during the present life. Mind is beginningless like the self, but is not eternal like it. It has an end. It ultimately merges into its material cause, i.e., primordial nature, when its purpose, which is the release of the self, is fulfilled.
Mind goes out through the doors of the cognitive senses and reaches an object of experience, assuming its form. As a result of it, a fluctuation arises in buddhi. The more perfect the assumption of the form of the object by mind, or more exactly, by the manas component of the mind, the more clear and distinct the fluctuation arising in buddhi.
Mind has the capacity to reach any object far or near, and not only a present object but also an object which existed in the past or which may exist in the future. And it can do this even without the agency of a cognitive organ. But such unhindered capacity can reside only in mind which is pure like a crystal clear.
Mind of most us is stained and smitten by two types of impurities, namely, the afflictions and the traces of past experience. Hence, it cannot assume the form of an object perfectly and clearly.
Mind is compared in Yoga to a river which flows either in the direction of virtue or else in the direction of vice. When, by the practice of Yoga, impurities are washed away and sattva guna predominates, the mind river starts flowing towards emancipation. For this reversal of flow, Patanjali has recommended the practice of kriya yoga,which helps mind steady in the state of meditation.