Knowledge of the external world and life in the world relies on the sense-organs, the nervous system and the brain in order to acquire information and process it, and then the mind organizes this information, categorizes and draws conclusions. Yogic knowledge however relies on a different process of inward view, and requires getting in touch with subtle senses and energies, and learning how to understand and interpret them. Yogic knowledge focuses on what stands behind the outer world and its appearances. The process involved implies that the normal methods of acquiring knowledge will no longer be able to adequately understand or judge the results.
Sri Aurobindo sets forth three steps that the yogic practitioner must undertake to prepare for this new way of seeing and knowing: “It does this by three movements each necessary to the other, by each of which the others become complete,–purification, concentration, identification.”
Purification does not mean what it ordinarily is taken to mean. It is not just some outward cleansing process, nor even a process of moral development, although these may indeed be steps undertaken along the way to help create the necessary instrumental basis. “The object of purification is to make the whole mental being a clear mirror in which the divine reality can be reflected, a clear vessel and an unobstructing channel into which the divine presence and through which the divine influence can be poured, a subtilised stuff which the divine nature can take possession of, new-shape and use to divine issues. For the mental being at present reflects only the confusions created by the mental and physical view of the world, is a channel only for the disorders of the ignorant lower nature and full of obstructions and impurities which prevent the higher from acting; therefore the whole shape of our being is deformed and imperfect, indocile to the highest influences and turned in its action to ignorant and inferior utilities. It reflects even the world falsely; it is incapable of reflecting the Divine.”
Sri Aurobindo, The Synthesis of Yoga, Part Two: The Yoga of Integral Knowledge, Chapter 25, The Higher and the Lower Knowledge, pp. 493-494