Jnana yoga. The yoga of discrimination and absorption.
There are four major paths to self-realization.
Of the four, jnana yoga, from the point of view of the beginner, is the most difficult. Jnana yoga is the graduate school of self-discovery. Ordinarily in spiritual practice one begins by practicing bhakti, the path of love. The path of love leads to the path of self-giving. The third pathway in the normal course of evolution is jnana yoga, discrimination and absorption. Mysticism, the fourth way, is not practiced by all. It's a left-handed path. It doesn't necessarily follow in the sequence of the others. Some persons follow the ways of mysticism, some do not, but normally the three paths are covered in this order: love, selfless giving and discrimination and absorption.
Discrimination means seeing that which is real and knowing that which is unreal. That which is real is that which is eternal, that which lasts forever. That which is unreal, or less real we might say, is that which is transitory, temporal, that which does not last but erodes in time. The yoga of knowledge is a way of reflection. The central question that we ask ourselves again and again is, "Who am I?" To find this out it is necessary to meditate, to still our thoughts and to go within. We discover, ultimately, that we are the self, we are eternity.
There are a number of different approaches that we can use when we practice the yoga of knowledge. The first is elimination. What we do basically is to examine everything in existence and we come to see that everything that exists is transitory and is temporal. It doesn't last. That which is left over is eternal and that is our real self. So we look, for example, at nature and we see that the creations of nature - plants, animals, human beings, planets, universes - all the things in nature are transitory. They may endure for a moment or perhaps billions of years, but ultimately they fall away, they don't last. So if we look at absolutely everything in the universe and we eliminate all of those things, then that which is left over is God, is eternity, is the Self.
You can learn that which is right and useful and that which should be avoided at your current stage of evolution.
Another way the reflection of knowledge works is to see that there is nothing that is not God. That is to say, when we talk about self-realization, realizing the Self and coming to know that which is, we're talking from the point of view of limitation of the mind. The mind perceives everything in a limited way. The mind is bound up with the ego. The ego has limited perception. Real knowledge or wisdom is to see that you are that - you are eternity. To talk about realizing the Self in a way is discontinuous because there is nothing but the Self, there is nothing but realization. There is really no one to realize the Self. The illusion of self-hood, of an ego, of a separate identity, is false. There is nothing but eternity - eternity has always been and eternity will always be. To realize the Self involves an action. It implies that there is something to realize, that there is time, that there is a temporal world and that Self is not yet realized, but will be realized by the actor through action. This is not the case. There is nothing that is not the Self. The Self does not have to be realized. The Self eternally is. There is nothing but the Self. This is the knowledge that comes through discrimination.
On the pathway of knowledge we view life as in a dream. We feel that all of this world is a dream. Just as when we go to bed at night and we fall asleep and we dream, and in the dream we can have experiences that seem to have a great deal of substance. They're solid and visceral, but upon waking from a dream - even the most horrible nightmare which filled us with fear, the most beautiful dream that filled us with the greatest joy - all of these dreams fade away. In a dream we can be very thirsty and we can have a drink of water and in the dream our thirst will be satisfied, but upon waking from the dream both the thirst and the satisfaction fall away. Everything and nothing falls away. So when we wake from the ignorance of this world, the dream of existence - the dream of perception, seeing ourself as a separate body, as an ego, as an identity, as a person - this falls away. All of the experiences that we have ever had fall away. The ideas of life and death, of rebirth, of reincarnation, karma, God, truth, knowledge - all these things fall away. While we're in the dream these are useful notions, but at the end of the dream, on the other side of the rainbow, there's only light, undifferentiated reality. In that undifferentiated reality of the self there is lasting joy, eternal bliss. All the phantoms of existence fall away.
To realize the self the mind must become very strong. On the path of knowledge we develop the mind through constant discrimination. Discrimination means inner reflection. We have to look within the self and fathom it. We have to constantly ask ourselves, "Who am I?" We have to remind ourselves that we are not the transitory body, we are not the person who is having experiences, we are not affected by action or inaction. We must constantly remind ourselves that we are eternity, we are infinite, we are beyond birth, we are beyond death. Birth and death are illusions, they are part of the dream. On waking from the dream we see that birth and death, the sense of self, the sense of others, all these things fall away - in the white light of eternity there is only eternity.