Without realizing what is Self in actuality, it is difficult to know 'What is non-self ? +

First, know ‘What is the Self’ and ‘What is non-self’ for sure. Without realizing what is Self in actuality, it is difficult to know  'What is non-self ?'.

It really depends on his inborn natural capacity to understand and assimilate Advaitic wisdom.  Sage Sankara’s wisdom is a Self-examiner, to test oneself to discover how near to Gnana he has approached and what progress has already been made on the path, and what still remains to be done.  It sets up a criterion for Self-judgement.   There are millions in search of truth but one in million will be able to grasp it.

In fact, Sage Sankara states a paradox- the world is and is not. It is neither real nor unreal. It leads us to recognize the existence of Maya (illusion). He thinks that the world is illusory from one perspective and from the second it is nothing but Brahman (God in truth), itself in manifestation. This apparent world is Maya and has its basis in Brahman, the Eternal. It looks as real. It has names and forms and actually, it is not real In the light of true knowledge, it disappears and Self-alone shines as real. However, Sage  Sankara's Mayavada has not been accepted by many preachers and philosophers.

When Sage Sankara says clearly, the universe is not real. He says that Brahman and Atman are one. The ultimate and Absolute Truth is the Self, which is one though appearing as many in different individuals. The individual has no reality. Only the Soul, the Self is Real; the rest, mental and physical are but passing appearances, then it indicates the form (waking or duality or mind) is unreal and the formless soul (consciousness or soul) is real.  Therefore, only Atman is real because there is no second thing that exists other than Atman, which is in the form of consciousness.

Sage Sankara says the universe is not real, so, he is indicating to study the universe. He is trying to help you to realize the unreal nature of the universe. He is talking about the ultimate truth hidden by the universe.

Sage Sankara says Atman is Brahman which means the Atman is the ultimate truth or Brahman. And the Brahman is God.

You cannot understand Sage Sankara; right now because your understanding is dualistic it is not possible to realize the non-dualistic truth with dualistic understanding unless you inquire into the nature of the universe.  

That is why Sage Sankara says you must first know what is before you. If you cannot know that, what else can you know or understand? If you give up the external world in your inquiry, you cannot get the whole truth.

Sage Sankara says the transparent Truth of the Self, which is hidden by the illusion, is to be attained through the instructions of a knower of Brahman, (Gnani).

First, know ‘what is the truth’ and ‘what is untruth’ for sure. Without realizing what untruth truth is, it is difficult to know what truth is.

Sage Sankara: ~ VC~.63: "Without knowing and examining the universe, one can’t know the Truth, as the idea that the external world exists, won't go. It can go only by an inquiry into the nature of the external world.

Sage Sankara says: ~ “What is accepted without a proper inquiry will not lead a person to the final goal. On the contrary, such acceptance will result only in evil, something which is detrimental to our spiritual progress. 

The universe hides consciousness. The universe is like a cloud and the consciousness is like water hidden by the cloud. The cloud has no existence without water. In the same way, the universe ceases to exist without consciousness.

Remember: ~

The ‘I’ is the universe. Without the ‘I’ the universe ceases to exist.  The Soul, the ‘Self’, and the universe are one in essence because the universe is nothing but an illusion created out of the Soul, the Self, which is present in the form of consciousness.

This universe is only the veil of ignorance on the Soul, the Self, which is present in the form of consciousness. The Self is not you but the Soul, which is hidden by the universe. The Soul is hidden by the universe because the universe is merely a dualistic illusion or Maya created out of the Soul, which is present in the form of consciousness.

Sage Sankara: ~ “VC~ All this universe which through ignorance appears as of diverse forms, is nothing else but Brahman (Consciousness) which is absolutely free from all the limitations of human thought.

When you finally realize the ‘‘Self’ ‘is not you but the ‘‘Self’’ is the Soul then you will realize the world in which you exist is merely an illusion created out of the Soul. The Soul is present in the form of consciousness.

Sage Sankara says: ~VC-47 All the effects of ignorance, root, and branch, are burnt down by the fire of knowledge, which arises from discrimination between these two—the Self and the non-Self.

Remember: ~ All is consciousness. The whole universe is consciousness. From consciousness, the universe comes. When the universe disappears, consciousness still remains without form, time, and space.

Until you think you are an individual separate from the world and the world existed prior to you and you are born in it afterward ignorance will prevail as a reality. Till ignorance is there the universe prevails as a reality. Until the universe prevails as a reality religion thrives.  : ~ Santthosh Kumaar