You and I  

You rely on what I say about you (as do I).
You use me for my purposes I'm ignorant of.
You are given to utter what I must intimate.
You are the Urtext: I have done the illustrations.
You are the ultramarine in which I am enisled.
You are the ultimate: I'm intermediate, and so
If you are Ithaca then I must be Ulysses;
I roam indiscriminately toward your urgent shore,
I learn inductively what is understood for you.
I improvise over your recurring undersong.
In and out my mind moves while you have your ups and downs.
I illuminate the darkness that you usher in.
I am a bad liar; you are as good as your word.

--John Hollander, from Powers of Thirteen (see also here and here)