what's wrong with Maybe?

I have refused to live
locked in the orderly house of
     reasons and proofs.
The world I live in and believe in
is wider than that. And anyway,
     what’s wrong with Maybe?

You wouldn’t believe what once or
twice I have seen. I’ll just
     tell you this:
only if there are angels in your head will you
     ever, possibly, see one.

-Mary Oliver, The World I Live In