You'll find this drawing in visual perception books. Is it a rabbit looking left or a duck looking right? Suppose that you only noticed the duck. You might say "Even I could do a better duck than that".

Just as the drawing isn't "really a duck", so some poems aren't about just one thing. Saying that "the duck could be better" (without considering the consequences of the change for the rabbit) misses the point.

Of course, a poem is full of compromises, but the rabbit/duck is an example of a situation where the two aspects have equal status. Were the conflict between form and content, for example, or one aspect was on the surface and the other somehow hidden, then the decision about which aspect should be damaged for the sake of the other might be clearer. But here, both aspects are equally plain, though one may turn into the other even as we look.

The example challenges simplistic views on symbol-world correspondences. Representationalism isn't abandoned, it's subverted. People who don't find the correspondence between words and the world problematic object to such work because they think

• it's better to do one thing well than two things badly — By do one thing the person presumably means draw one object or write about one object. However, the work would lose much of its point were it replaced by 2 separate, juxtaposed pieces. Art can do more things than merely represent objects. Perhaps the rabbit/duck is doing its own thing well!
  

• it's better to write about real things than just to play with words — Words matter to poets. Sometimes the connection between words matters too, independent of their meaning (as with rhyme). The connection between words and the world matters, and it's this connection which is the focus of the kind of works under discussion. Sometimes we complacently assume the transparency of language. Puns and illusions remind us that our senses can be fooled, that we'd do well to linger on the language sometimes rather than look straight through it.

That said, the Rabbit/Duck remains an example from psychology books. Art objects exist though. Dali (e.g. 'Slave Market with invisible Bust of Voltaire', 1940) and in particular Escher are amongst the practitioners. The precise Escher puns are hard to replicate in words, though examples exist.

Still lonely, a boy far from shore, knowing
it was finished, all over, gone. No missed ache.

...

still only a boy, far from sure. No ring —
it was finished, a lover gone. No mistake
(from 'Not Waving')

More common is where one aspect dominates, but there's a strong consistent allusion.

Our words engage quite cleverly sometimes
across the dark square room,
all disagreements so cautiously unsaid
in a white maze where we never meet
(from 'No more cross words')

Updated Mar, 1997 (quotes are from the author's poems)