The ultimate reality is that there is no separate Me. We are It; or as Vedas say, Tat Tvam Asi (Thou Are That, the all-encompassing Totality)! How do we know that? We can begin with accepting it as a conjecture from the ancient scriptures, written by ancient seers and the numerous seekers that have come before us, when they say that Tat Tvam Asi or Aham Brahmasmi (I am Totality). We then verify this truth for ourselves by experiencing in our own subjective lives.
Why should we trust the cognitions of ancient seers? Why should we trust our fallible subjective experiences? Why should we trust an objective truth about our subjective selves? These are three primary ways of verifying truth claims, also called darshanas in Vedas. These are also very good questions. All logical chains must with some axiom(s).
We can start with the axiom that Consciousness is primary. Consciousness is simply conscious of itself. It is all-pervasive, like a quantum field of intelligence. It is matter and energy in an interchangeable manner. Consciousness is the unified field of all the laws of nature and all those laws can be experienced in one’s own subjective awareness. It is the knower, the known, and the process of knowing, all rolled into one. Thus ‘we’ can know ‘ourselves’ by ‘ourselves’. The way to know one’s self is by stilling one’s mind and refining one’s perceptual ability to directly see the subtler reality, just as one sees the depth and clarity of a lake when it is calm. Newton inductively discovered the laws of gravity within his own consciousness when his attention fell on the falling apples.
Subjective personal experiences are usually the most powerful ways of knowing at a personal level. This can be just as empirical and personal data based as the scientific method. If doing some action, such as waking up early or doing a certain meditation regularly, makes one feel healthy or blissful, one would want to do it again and again. One’s personal experiences can override the received wisdom as well as scientific research and develop into personally useful habits.
Scientific method also relies of an axiom, that of materialism, i.e. material reality is primary. There is no such thing as subjective consciousness except as an ephemeral emergent property of materials. Thus, scientific inquiry precludes the existence of any such thing as an independent self that has a body and a mind? The organizing logic is that of self-preservation. What is the self that is being preserved? There is no cogent scientific theory of life beyond physical existence. There is no realizing the self, only a process of actualizing the ‘hidden true potential of the self‘ without objectively defining that potential.
It is best when all three modes of knowing reinforce each other. It is good to read the scriptures, undergo scientific education, and then verify the received truths in one’s own experience.