We engage in an act of poetic meaning-making forewarned and forearmed. The warning is necessary: readers will have to roll up their sleeves and collaborate meaningfully with the poet to make the poem. Hence, the poet needs to play fair: leave the right margins unjustified and lots of white space around the piece. That signifies" Poem: Beware. Reader, if you are not willing to do your part, turn the page."
Poems omit, hint, and sometimes -- as Plato remarked -- they may even lie. The reader has to accept that the writer is not exactly playing fair. But the reader has been fairly warned and should know what is expected and be willing to provide it, as the poet took special pains to provide something worth struggling with. The two thus form co-contractors, bound to work together to make the poem.