The Appearance of the World ~ Thomas Matzinger
Consciousness is the 'appearance of a world'. The essence of the phenomenon of consciousness experience is that a single and unified reality becomes present: If you are conscious, a world appears to you. This is true in dreams as well as in the waking state, but in dreamless deep sleep, nothing appears: the fact that there is a reality out there and that you are present in it is unavailable to you; you do not even know that you exist.

Consciousness is a very special phenomenon, because it is part of the world and contains it at the same time. All our data indicate that consciousness is part of the physical universe and is an evolving biological physics plus biology -- more than a fantastically complex, dancing pattern of neural firing in your brain. What sets human consciousness apart from other biologically evolved phenomena is that it makes a reality appear 'within itself'. It creates inwardness, the life process has become aware of itself.