The Thing Itself
From a summary of Sartre’s Being and Nothingness:
“The human can never know being as it truly is, for to do that, one would have to be the thing itself. To know a rock, we have to be the rock (and of course, the rock, as a being-in-itself, lacks consciousness). Yet the being-for-itself sees and intuits the world through what is not present. In this way, the being-for-itself, already wholly free, also possesses the power of imagination. Even if absolute beauty (to Sartre, the absolute union of being and consciousness) cannot be apprehended, knowing it through its absence, as in the way one feels the emptiness left by a departed loved one, is its own truth.”
— Anonymous author at sparknotes.com