Dattatreya's Song of the Avadhut :~ Non-duality is taught by some; some others teach duality. They don't understand that the all-pervading Reality.+

Dattatreya's Song of the Avadhut 1.36-42:~ Non-duality is taught by some; some others teach duality. They don't understand that the all-pervading Reality is beyond both duality and non-duality.

This does not mean that consciousness, which is the ultimate truth or Brahman is a negative concept or a metaphysical abstraction, or a nonentity, or a void.

Consciousness is second to none. Consciousness is not another. Consciousness is all-full, infinite, changeless, Self-existent, self-delight, Self-knowledge, and Awareness. Consciousness is the essence. Consciousness is the formless knower of all that is known. Consciousness is the formless Seer and the Seen. 

Consciousness is transcendent and formless Witness. Consciousness is impersonal and without attributes, formless, without special characteristics, immutable, eternal, and non-agent. Consciousness is above all needs and desires. It is always the Witnessing Subject. It can never become an object as it is beyond the reach of form, time, and space. Consciousness is non-dual, one without a second. It has no second thing besides it. Consciousness is destitute of difference, either external or internal. Consciousness cannot be described, because description implies distinction. 

Consciousness cannot be distinguished from any other than it. In consciousness, there is not distinction between substance and attribute. Awareness is the very essence of consciousness and is the ultimate truth or Brahman or God in truth.

The attributeless consciousness is impersonal and pure. Consciousness becomes a personal or attributed consciousness only through its association with illusion, which appears in the form of the mind or the universe (waking or dream).  

Attributed consciousness and attributeless consciousness are not two different consciousnesses. Attributeless consciousness is not the contrast, antithesis, or opposite of attributed consciousness. The same attributeless consciousness appears as attributed consciousness. The mind and the soul are one in essence.  The essence is consciousness.  Thus, consciousness is second to none.

The attributed consciousness appears in the form of the mind. The mind is in the form of the universe. And the universe appears as a waking or dream. Thus,  the mind, universe, waking, or dream are one and the same thing. 

The universe is a reality from the standpoint of the waking entity.  The universe is unreal from the standpoint of the Ataman, which is attributeless consciousness.

The practical life within the practical world is the reality from the standpoint of the waking entity, which is attributed to consciousness. It is the same consciousness from two different points of view.

Attributeless consciousness is real and eternal, the ultimate truth from the transcendental standpoint; attributed consciousness is the illusory consciousness that appears as the universe and is a reality within the illusory waking experience.

The universe is an illusion from the standpoint of the Atman or consciousness. The practical life within the practical world is the reality within the illusory waking experience. The three states are the product of ignorance. 

Ignorance is the cause of experiencing the illusion as reality. When ignorance vanishes through wisdom then consciousness alone will prevail as the ultimate reality or Brahman or God in truth. Thus, consciousness is absolutely real and eternal.

The illusion or the mind or the universe, which appears as waking or dream is the product of ignorance. The unchanging consciousness appears as the changing mind through illusion. Illusion or mind is a mysterious indescribable power of consciousness that hides the real and manifests itself as the unreal: mind or illusion is not real, because it becomes unreal when one attains Self-knowledge. 

The mind or waking remains a reality until ignorance is there. When nondual wisdom dawns then the waking experience becomes unreal. The superimposition of the illusion on consciousness is due to ignorance.:~Santthosh Kumaar