Modern man appears to have acquired admirable knowledge in various field of investigation into the material world. Man has to accept the fact that what has been acquired as scientific knowledge is but infinitesimal or superficial nothing considering to the mystery of his own existence. Above all, the acquired scientific knowledge and power does not quench his thirst, to know the spiritual realities of his own existence.
Knowledge unfolds itself within the experience of diversity. The experience of diversity (waking or universe) is but the illusory an expressive imprint of the journey of the spirit or soul in its search for the knowledge of itself. The truth manifests in stages according to the receptivity of the aspirant. On the mental plane it manifests as self, which only the realized mind could observe it. On the physical plane it is as an advanced seeker or perfect man of knowledge. His very presence among men awakens then to the awareness of what they should and may become.
The self knowledge or Brahma Gnana or Atma Gnana comes by and through inquiry, analyzes and reasoning on the true base, not by intuition, love and inspiration. It is the inquiry and reasoning makes one transcend the dominion of intellect, which is physical based and gain the state of complete annihilation of the false self, and it is the state that ends in the union with the true self, which is Atman or consciousness.
Inquiry and reasoning makes one remember the eternal true identity and making him feel less bound, in his onward march, by the trammels of physical limitation, till he reaches where he can rise himself to the realization of the ultimate truth or Brahman. When the self makes itself free from all the manifoldness of the experience of diversity, it is able to view and the judge the illusory experience of duality on the base of the its formless non-dual true nature. Then only it is possible to realize there is no second thing other then the soul or consciousness in the whole experience of diversity. Thus one can conclude that the whole experience of diversity is only a mental state, which disappears and reappears.
The first begin with gnosis and ends with the complete passing away of total annihilation of the mind ( waking or universe or I).
The second begins with at the moment of the annihilation of the experience of diversity (I) succeeded by abiding or the union of the mind (I)its non-dual substance, which is the true self. The union with substance is the self realization or self knowledge.
The aspirant who gets the self knowledge becomes emblem of perfection and able to view and judge the whole experience of diversity ( mind or I) from the standpoint of the formless non-dual true identity, and realizes the fact that there is no second thing other then the Atman or consciousness in the whole experience of diversity. The whole experience is mere mirage created out of single substance thus the experience of diversity has no reality in it, when it is viewed and judged on the base of Atman.
The third journey begins from base of the true self, which is Atman or consciousness and ends with the state of the perfect non-dual-hood. He who comes to the final journey becomes the center of the experience of diversity form where it has been erupted. Thus he becomes free from the burden and bondage of the experience of diversity (I) in the midst of the experience of diversity consciously.
The aspirant while undergoing all these stages in the pursuit of truth has to pass through various level of understanding and cross all the fatter and obstacles to real his non-dual destination.