In the title poem of her absorbing fourth collection, The Casual Perfect, Lavinia Greenlaw lists some of the desiderata of the state she's talking about, including "A gesture in musical time", and "Description in action". The hope is to evade the familiar channels of interpretation, to exclude anecdote, to let the subject be itself rather than subject to the allegorising habit which can stifle experience until it is merely exemplary. Amen to all that. To make the quick of experience present in a poem is the philosopher's stone for many modern poets.

There is a naive version of this  the one that Yvor Winters called the Fallacy of Imitative Form, whereby for example Lawrence's snake is said to be, well, snaky; and then there is the interesting version, the paradoxical one Greenlaw is concerned with, of which Elizabeth Bishop was a leading exponent, whereby a vast self-awareness is directed at letting things be  landscapes, climates of feeling, people. In "Saturday Night", the sight of girls dancing in the road leads Greenlaw to conclude: "You who pass by can watch / but not enter the world of this place. / You know nothing of its way / of growing tree from shadow / so that all is fixed and root. / You who pass by, pass by." The Yeatsian "pass by" seems at once a joke and a rebuke to presumption.

The figure of the dancer recurs in "Silent Disco": "The look on her face is filling the room. / Someone else would describe it as joyful, / only to you it is space she is taking / and you will never have seen her so clearly, / so within, she forgets herself as seen. / She is pure direction, she is line and ring." In both poems "you" is something more than the familiar demotic replacement for "one": it is the observer, not the observed, who is incomplete. But this is not to say that "you" will have no effect, for example in the imminent developments in "Empty Metaphor". "The last room was a hall of mirrors / where my child stepped past. // Nineteen  about to be described / and yet to meet her explanation. // At the point of exchange / she became so unknown, so clear // that I could not tell glass from air." The background of fairytale may be changing into something grimmer, since the final chamber could be that of Bluebeard. The poem, of course, gains from leaving this unsaid.

What to leave out is a question Greenlaw seems to have considered with great care. "The End of Marriage" takes a bare-bones approach to generate a conclusion in which comedy and horror are hard to separate: "It is often five o'clock. /Her husband has contracted not / to speak of her and she has forgotten / where to go. Where does everyone go?" "The Catch", one of the most memorable pieces in the book, is so economical that it will probably incite some to the very kind of narrative reconstruction that the poem seems designed to prove irrelevant. But meanwhile the final stanza involves a sly recusatio  the device whereby the poet states her inability to deal with a subject, while at the same time dealing with it. It is, she suggests, the very idiosyncrasy that draws her away from "theme" to "variation" that enables the poet to speak of fundamental matters. To be otherwise might involve a cost to the art which enables anything to be grasped at all. "One day I'll learn to listen / to the city beneath the snow, / the agony in the irony, / the lover as I go."

To let things be involves Greenlaw in reconsidering the relationship between self and the world. In her account, offered in landscape pieces such as "Blakeney" and "Severn", we neither stand in a connection of privileged mutual enchantment with our surroundings, nor serve only as aesthetic decorators of them. We are inescapably part of the weather and the landscape. This position is not original (how could it be?) but Greenlaw renders the knowledge that "There is no way home", since we are already here, with an unsparing sensuality and a satisfying, slow-burning music.

In "Blues (That's another Sunday over)" she also proves able to apply her talents to that state of negation that must overtake almost everyone from time to time, when the resources of imagination, curiosity and humour seem inadequate to the facts of the matter. A black, exasperated amusement preserves the poem from complete inertia: "Scene from a novel. Dust falls. / The page won't turn, the stranger won't call. / A town that's sinking sinks us all. // The one road out heads towards sunset. / The young drive as if overtaking death / and the old as if following the dead." Unwelcome though the mood may be, it seems to serve here as a charm against the humourless, Pollyanna-ish piety to which some poets with broadly similar aesthetics to Greenlaw are sometimes prone. Her own intense literariness is always bent on finding its way back to life as well as over the page. With The Casual Perfect, Lavinia Greenlaw has come into her own.

Sean O'Brien's November is published by Picador.