My soul lives in my body's house,
And you have both the house and her --
But sometimes she is less your own
Than a wild, gay adventurer;
A restless and an eager wraith,
How can I tell what she will do --
Oh, I am sure of my body's faith,
But what if my soul broke faith with you?

Sara Teasdale

http://www.poemhunter.com/poem/doubt/