There’s no way to step outside consciousness and measure it against something else. Science always moves within the field of what consciousness reveals; it can enlarge this field and open up new vistas, but it can never get beyond the horizon set by consciousness. [And] since consciousness has this kind of primacy, it makes no sense to try and reductively explain consciousness in terms of something that’s conceived to be essentially non-experiential, like fundamental physical phenomena. Rather, understanding how consciousness is a natural phenomenon is going to require rethinking our scientific concepts of nature and physical being.
According to the yogic traditions of Indian philosophy, consciousness is that which is luminous and has the capacity for knowing... Luminous means having the power to reveal, like a light. Without the sun, our world would be veiled in darkness. But without consciousness, nothing could appear. Consciousness is fundamentally that which reveals or makes manifest because it is the crucial precondition for appearance. Nothing, strictly speaking appears unless it appears to some consciousness. Without consciousness, the world can’t appear to perception, the past can't appear to memory, and the future can’t appear to hope or anticipation. The point extends to science: without consciousness, there’s no appearance of the microscopic world through electron microscopes, no appearance of distant starts through telescopes, and no appearance of the brain through magnetic resonance imaging scanners. Simply put, without consciousness there’s no observation and without observation there are no data.From the introduction and chapter 1 of Waking, Dreaming, Being by Evan Thompson (2014)
Added after 30 December 2014: Alva Noë has this note on the book
Image: Starry Night by Vincent van Gogh (1889) via WikiArt