The New York Trilogy Part II

'But the present is no less dark than the past, and its mystery is equal to anything the future might hold. Such is the way of the world: one step at a time, one word and then the next. There are certain things that Blue cannot possibly know at this point. For knowledge comes slowly, and when it comes, it is at great personal expense.'

[...]

'Blue watches Black, and a little of anything happens. Black writes, reads, eats, takes brief strolls through the neighbourhood, seems not to notice that Blue is there.'

[...]

'Writing is a solitary business. It takes over your life. In some sense, a writer has no life of his own. Even when he's there, he's not really there.
Another ghost.'

[...]

'Does he know you're watching him or not?
Black turns away, unable to look at Blue anymore, and says with a suddenly trembling voice: Of course he knows. That's the whole point, isn't it? He's got to know, or else nothing makes sense.
Why?
Because he needs me, says Black, still looking away. He needs my eye looking at him. He needs me to prove he's alive.'

[...]

'And from this moment on, we know nothing.'

(Paul Auster, Ghosts)