Knowing the truth” means the removal of ignorance.+

When you realize you and the world in which you exist as an illusion created out of the invisible Soul or consciousness then you will realize consciousness alone is real and eternal; there is no second thing that exists other than consciousness.

It is not as if something that was not consciousness suddenly becomes consciousness. Rather, "knowing the truth” means the removal of ignorance about one's own existence as consciousness. Thus, to "know the truth” is to "be consciousness."

Consciousness is ever-present. Without consciousness, the world, in which you exist ceases to exist. Consciousness is Self-evident. It is not established by extraneous proofs. It is not possible to deny consciousness because it is the very essence of the one who denies it. Consciousness is the basis of all kinds of knowledge, presuppositions, and proofs. Consciousness is everything. Thus, consciousness is the ultimate truth or Brahman.

The look of an object will depend upon the medium through which the observer views it. In fact, our mental and intellectual conditions determine the world, observed and experienced. The commoner viewing the world will see differently from a Gnani viewing the same world. Each one interprets the world that they see in terms of their existing knowledge. The commoner sees everything based on the ego, therefore, experiences the birth, life, death, and the world as a reality, whereas a Gnani sees everything as consciousness and he is fully aware of the fact that, there is no second thing that exists other than the Soul or consciousness. : ~ Santthosh Kumaar