VISUAL ARTS:AS BARACK OBAMA controversially commented a couple of weeks ago, people cling onto all sorts of things. Often people who are art lovers and well versed in the breadth of art practice tend, when they are looking a painting, to cling onto an image.

They will find little traction in the Hugh Lane gallery's exhibition Unique Act which includes work by five painters, all negatively and perhaps defiantly termed "non-figurative."

One could say that the show demonstrates the range of contemporary non-figurative painting, but that sounds a bit defensive, which isn't the mood that comes across.

The elephant in the room is the word "abstract" which has had bad press since the advent of post-modernism and, it is true, is in any case problematic, particularly in suggesting a degree of removal from the real world into a realm of geometric purity, perhaps.

All of the work in Unique Act, for all the absence of figures and representation in any conventional sense, is firmly rooted in the world in various ways. Strangely enough, you may find it takes longer to look at, and see, a non-figurative painting than a figurative one, precisely because it doesn't provide you with a representational cue to which you can duly respond. Unfortunately, a common response is for a viewer not to bother looking at all.

In terms of age and experience, the five artists cover a lot of ground. One, Frederic Matys Thursz, died in 1992 after heart surgery. Born in Morocco in 1930, from the age of about 10 he was brought up and educated in the United States where he went on to teach, living between New York and Paris.

An exceptionally focused and highly regarded abstract painter, virtually the entire output of his artistic maturity was based on the proposition that paint itself, as a bearer of colour, can convey feeling and meaning. He rejected the apparently common sense idea that a painting which is, say, entirely red, can be described as monochromatic, on the basis that a single physical instance could not encapsulate a colour.

Accordingly his own paintings are for the most part intensively worked, built up, scraped back and rebuilt layer over layer so that they achieve high levels of chromatic density and physical presence.

They often seem to have a tragic quality in the way they are scarred and injured, suggesting endurance and mortality. Our potential response to them is necessarily subjective and depends on whether we are willing to accept the artist's clearly heartfelt belief in the spiritual core of the work.

Seán Shanahan, who is best known for his intensely coloured monochrome panel paintings could surely be regarded as an artistic relation of Thursz's. The surfaces of his work, which can appear completely flat and impassive, are usually, on closer inspection, open to the variation and fallibility of touch. It's notable that in recent years he has become increasingly attentive to the architectural settings of his paintings. Exhibitions have been expressly tailored to particular venues, including, in 2003, Vidar (a reference to Jospeh Conrad), in the Hugh Lane itself.

All of this is worth mentioning because several of his pieces in Unique Act depart conspicuously from that attentiveness to architectural sensitivities.

The four constituent panels, each a different colour, that make up Mike B, for example, abut each other at different heights, so that your eye-line jumps up and down as you negotiate them. It's a bold departure on Shanahan's part, not least because the new work, when viewed in proximity with his single-panel monochromes, actually has the effect of destabilising them.

Where the single-panelled Bud, for example, positively anchors the wall it hangs on and allows us to experience an expansive colour field at leisure, Mike B not only edges us out of each of its adjacent colour fields but sets its cumulative energy against the architectural framework.

The upshot is that something is gained and something is lost: the expanded possibilities of a dynamically unstable pictorial vocabulary come at the expense of sure, incremental advances within a well-tested idiom. It will certainly be interesting to see what Shanahan does next.

The jagged format of his multi-panel pieces recalls what was, for Seán Scully, a breakthrough work, Backs and Fronts from 1981. Scully is the best-known painter in the show and his work has an assurance and authority that is often linked to its assertiveness. At first glance the blocks of toned-down colour from which his compositions are built might seem to substantiate this view, but look again and it becomes apparent that the paintings are much more complex than that.

In fact their effectiveness depends on other equally important qualities, including a feeling for the atmospherics of light and, more surprisingly perhaps, a completely undogmatic openness, so that the surfaces are imbued with a tenderness of spirit underwritten by aesthetic resolve.

Born in Chile, Carmengloria Morales has long been based in Italy, and the habitual formats of her work - diptychs, tondos and arches - hark back to classical religious art.

She builds up her paintings with very broad, forceful, short, brusque brush-strokes, overlapping and at approximate right angles to each other. Her diptychs feature a painted left-hand panel and a blank right.

That might suggest an evocation of plenitude and nothingness, but a blank canvas isn't nothing, it is an object in the world - it ages, it accumulates a history as a thing and her use of the device has not been entirely convincing.

The heavily textured tondos in the Hugh Lane are striking and intractable. Colours and marks meet in her paintings but they remain unintegrated, giving the works an open, even raw quality.

It's sort of accurate, if not quite fair, to describe the work of New York-based Chicagoan Ruth Root as the lightest in the show. Her flat-coloured aluminium panels, hung flush with the wall, have a playful quality, partly because their lozenge forms recall the speech bubbles from comic-strips as much as more formal, high-art sources.

Actually it's a sign of artistic strength that she is able to incorporate lightness and humour in what she does.

There's also a retro, Art Deco elegance to the interlocking, overlapping patterns she makes and the palette she uses.

Unique Act is a rewarding, well-presented show, but remember to go with your mind as well as your eyes open.

Unique Act: Frederic Matys Thursz, Seán Scully, Carmengloria Morales, Seán Shanahan and Ruth Root, Dublin City Gallery, The Hugh Lane, Charlemont House, Parnell Square North, until May 25