"Consciousness can be likened to a disembodied eye (in a land where mirrors are non-existent). Such an eye cannot see itself for it is that which does the seeing—the functioning of sight. As is true of all the senses (including the mind, as it is a vehicle and synthesis of them), all that the eye beholds, it very literally is, since all objects of sight cannot be separate from the agency that is the seeing of them. When the eye looks to see itself, it can behold only the absence of itself; and it is this absence that is the foundation of all the objects of sight—the absence that allows and structures their existence. The perfection of functioning for eyes is not being in the way of (i.e., being absent to) what it sees. It is absolutely behind so that all things can be in-front-for-sight. To expand the metaphor somewhat: imagine spinning around trying to glimpse the back of your own head and forever seeing only that which is the perfect absence of it, i.e., what, of necessity by design, is always 180 degrees from the back of your head. But, strangely, this is the only way you can see the back of your own head, for it is connected, indeed inseparable, via its own absence, to all you do see. This is the mind-blowing way that emptiness (absence) and fullness (or form) are united. The Buddha put it thus, in the Heart Sutra:
Here, O Sariputra, Form is Emptiness and the very Emptiness is Form;
Emptiness does not differ from Form; Form does not differ from Emptiness.
Whatever is Form—that is Emptiness. Whatever is Emptiness—that is Form.
The same is true of Feelings, Perceptions, Impulses and Consciousness.
Here is the most profound and most challengingly subtle endeavor of all mentation. Paradox confounds the mind—runs it into an alley and sets it against itself. Naturally evolved to project outwards, to objectify the cosmos by isolating itself from its partner in creation, the mind sees Fullness in Absence, yet knows it not.