The impurities of the mind constitute the obstructions to the knowledge of this ever-present divine immortal dimension of man. These impurities are centred in the ego, in its attachments and aversions and bondage to the organic system. Search for truth, either in the external world which yields scientific knowledge, or in the internal world which yields spiritual experience, calls for the elimination of these impurities which alone gives the mind power to penetrate from the surface to the depths of nature, external or internal.