In Vedas the God has been described as:-

No one can prove the existence of god because whatever knowledge one has   of GOD comes from our old scriptures which were written by great spiritual saints, who are no longer present to testify their writings.

The scriptures it self declare that:    This Atman cannot be attained by the study of the Vedas, or by intelligence, or by much hearing of sacred books. It is attained by him alone whom It chooses. To such a one Atman reveals Its own form. [Katha Upanishad Ch-II -23-P-20]

People believe in old myths propagated by their religion. Every religion has propagated its own myth. Every religious belief contradicts other beliefs. It is mere blind belief accepted as truth without verification and evidence.  This causes division. Modern science has exposed many Religious dogmas as myth. All these dogma were introduced in primitive era   before people had the benefit of modern science. Science attempts to objectively discover how life works, and religion makes one blindly believe and cast his  burden on the blind belief without verification,  to live in peace and harmony in practical life  within the practical world. 

 Seekers main aim is to investigate both dual and non-dual experiences to find and define the underlying truth in everything, thereby realizing what the ultimate truth is.  Because of so many beliefs propagated by belief system, people think seekers of truth are   atheists because they do not accept the belief blindly. Seekers of truth believe the religionist and atheists both are believers because religionist believe in the belief of god and atheists believe in belief of no god.   

Pursuit of truth is all about accepting uncertainty and open questions and seeking for the things that are certainty. Believers and nonbelievers   will not accept anything other than their inherited belief system or accepted truth.  Atheists feel there is no proof for god’s existence. So atheist chooses to just believe there is no such thing called God. And religionists just believe in the existence of their conceptual god.  A Gnani is one who is fully aware of the fact that, the existence or non-existence of God cannot be proven on the base of physical self.  Therefore deeper understanding is necessary to understand and assimilate the truth about Gods existence to know what is supposed to be the God. 

In Vedas the God has been described as:-

  Sakshi (Witness)

  Chetan (conscious)

  Nirguna (Without form and properties).

The Soul/God further has been told as

  Nitya (eternal)

  Shuddha (pure)

  Buddha (omniscient)

   Mukta (unattached).

All the above are nature of the soul the innermost self therefore,  The Soul or  Self or Atman is God and God is Soul or  Self or Atman.

It means the ultimate truth is god.  That is Atman is Brahman.  That is the true self is ultimate truth. 

In Advaita Vedanta: - Brahman is without attributes and strictly impersonal. It can be best described as infinite Being, infinite Consciousness and infinite Bliss. It is pure knowledge itself, similar to a source of infinite radiance. Since the Advaitins regard Brahman to be the Ultimate Truth, so in comparison to Brahman, every other thing, including the material world, its distinctness, the individuality of the living creatures and even Ishvara (the Supreme Lord) itself are all untrue. Brahman is the effulgent cause of everything that exists and can possibly exist. Since it is beyond human comprehension, it is without any attributes, for assigning attributes to it would be distorting the true nature of Brahman. Advaitins believe in the existence of both Saguna Brahman and Nirguna Brahman; however they consider Nirguna Brahman to be the absolute supreme truth. 

Atman is the true self.   The true self or Atman is in the form of consciousness is ultimate truth and it is God.   

 The Atman is within the mind [universe] and mind [universe] is within the soul. The universe) is within the self and self is within universe. The chicken is in the egg and the egg is in the chicken. The tree is in the seed and the seed is in the tree. The same thing that was told by the Vedas was repeated by the Saint John (10-38)? Father is in me and I am in Father. Thus the father [soul/self] is our immediate, neighbour- love thy neighbour.  Therefore, one has to love the soul/Christ in order to become one with the formless spirit or soul or consciousness   or Christ which are the creator, sustainer and dissolver of the world/duality.  

Therefore, self-realization is necessary in order to realize the ultimate truth or god.  Self-realization is real God realization. 

In Isa Upanishad says:

MANTRA 10

Scholars say that the path of Avidya [performing Aganihotra and other sacrifices] and the path of vidya [worshipping gods and goddesses] produce different results. Wise men confirm this. [X]

Vidya and Avidya both are hindrances to Self-knowledge, but Vidya is even worse than Avidya. The word Vidya is used here in a special sense; here it means worshipping gods and goddesses. By worshipping gods and goddesses you will go after death to the world of gods and goddesses. But will that help you? The time you spend there is wasted, because if you were not there you could have spent that time moving forward towards Self-knowledge, which is your goal. In the world of gods and goddesses you cannot do that, and thus you go deeper and deeper into darkness.

Avidya is Karama and therefore a hindrance. You perform Avidya - i.e., you perform Agnihotra and other sacrifices. This is a roundabout way of purifying the mind, and it is also groping in the dark. But it may not have as heavy a toll on your time and energy as the other.

If the self –knowledge is the goal, then it means belief in conceptual gods and worshiping the belief leads to deeper ignorance. Religion and its prescription of believing and worshiping gods are recommended for those who are not receptive and ready to receive the self-knowledge.

 It proves that the concept of god, karma, heaven and hell are ideas created by religion, to help for those who are incapable of grasping. The concept of god and goddesses and karma are part of the ignorance. By worshiping god and goddesses one accepts the false self as true self, thus he is unfit for self-knowledge. Therefore concept of god is not the means to acquire the self knowledge. That is why Buddha rejected concept of God, religion and scriptures. 

Therefore, it is necessary to make sure why the religion, concept of god and scriptures are not the means to acquire Self-knowledge or Brahma Gnana or Atma Gnana.