Consciousness is unattainable to those who are not properly inquired, analysed and reasoned on the base of the consciousness as self. One becomes aware of the changeable nature of' the experience of duality (diversity) in which man and the world exist.
The experience of duality (waking) becomes non dual (deep sleep)and again becomes duality (dream) this process will go on until it remains as non-dual eternally (death). One has to know one which is aware of these dual and non-dual experiences. The dual (waking or dream) and non-dual (deep sleep) experiences are unreal, and one(witness)which is aware of these experiences which comes and goes is real. The witness is formless consciousness. And consciousness is apart from this experience, since all these experiences are an object to consciousness. Consciousness is within this experience as its formless substance and it is apart because it is not an entity or identity within these experiences.