Figures of speech can illuminate or emphasize. In John Keats's "beaded bubbles winking at the brim," those winking beads make the glass of wine more vivid, attractive and temporary. When Shakespeare says, "And with old woes new wail my dear time's waste," he implies that brooding is a destructive waste of time, like a bad argument in court.

But phrases and images have another, almost opposite way of working, too. They create mystery or disturbance or the inexplicable. Emily Dickinson's "I heard a Fly buzz -- when I died" will always have an effect you cannot quite fully describe. You will never see all the way through such language. When Eliot's Prufrock speaks of the evening "spread out against the sky/ Like a patient etherised upon a table," part of the power is the communication of a feeling we can name as numb and vulnerable. But just as important is what cannot be named, the inexhaustible nuances.

These familiar examples have their counterparts in new poetry: images that are satisfyingly clear in one way and excitingly inexplicable in another way. Here is a short poem from Dana Levin's new book, Wedding Day:

Ars Poetica

Six monarch butterfly cocoons

clinging to the back of your throat --

you could feel their gold wings trembling.

You were alarmed. You felt infested.

In the downstairs bathroom of the family home,

gagging to spit them out --

and a voice saying, Don't, don't --

The irrational part of the image, the nightmare quality, makes these lines memorable. The cocoons have a dream-reality, and within that reality is the further dream or imagining of the gold wings trembling. As in a good suspense movie, the ordinary setting magnifies the fear: "the downstairs bathroom of the family home." The Latin root of "infested" is "unsafe," and the voice saying the last two words values the unexpected, the new, over safety. Caution, instinct and good sense want to spit out the infestation of new life, but some other creative spirit, perverse or not, wants to see the unsafe cocoons open. The cocoons, that enfolded and alarming new life, are at once perfectly clear in meaning and perfectly enigmatic.

From another recent book, How We Sleep on the Nights We Don't Make Love, here is an utterly different image that works in a similar way. E. Ethelbert Miller is thinking about violence against civilians in Jerusalem and trying to examine that violence in relation to the courageous, embattled hero of nonviolent disobedience Rosa Parks. The word and image "bus" -- the "omnibus" or "for everyone," a public good -- provides the connection:

Rosa Parks dreams

Rosa Parks dreams about

a bus in Jerusalem. A headless

woman sits in her seat. There is no

driver today. The top of the bus

is missing. On the road a line

of bodies segregated from the living.

They sleep against a twisted metal

frame. Wild flowers stare from

a field.

In much that I read, what I don't understand is merely lost or confusing. In this poem, the limits of understanding become part of the point. The image becomes part of my craving to understand, part of a shadowy contest between fear and hope: fear of the violent forces in any conflict, and hope for victory by heroes like Parks.

An editorial about violence and nonviolence, or freedom and oppression, using these two images, might get into a snarl of difference and similarity. Similarly, a prose statement about an aesthetics of "infestation" might reduce the feeling of Levin's poem to mere platitude or babble. Embracing the irrational along with the rational, poetry can bring the sealed-off clarity of dreams into our world of actual speech. (Dana Levin's poem "Ars Poetica" can be found in "Wedding Day." Copper Canyon. Copyright © 2005. E. Ethelbert Miller's poem "Rosa Parks dreams" can be found in "How We Sleep on the Nights We Don't Make Love." Curbstone. Copyright © 2004.)