Hughie O'Donoghue's new exhibition, Corp, which opens at IMMA on Friday, draws together works, made over a period of 15 years, that exemplify his long-term preoccupation with the human figure. It is a big show, and necessarily so, because the Manchester-born painter routinely works on a monumental scale. And it will overlap with another major exhibition of his work, scheduled to take place in the RHA Gallagher Gallery next January.

This, too, will have the figure at its centre, and has been 12 years in the making. It will consist of a group of pictures under the general title Via Crucis, and forms the first part of a project to make a cycle of paintings related to the Passion of Christ. They were first exhibited in Munich in 1997 and, later that year, some of them were shown in Kilkenny during Arts Week. The January exhibition will mark the gift of the paintings to the OPW by the anonymous patron who commissioned them.

It makes sense to view the work in Corp with Via Crucis in mind, not least because of the recurrence of cruciform and sacrificial figures in the compositions, and because O'Donoghue really does paint as if it is a matter of life and death. He has a rare ability to unselfconsciously tackle the big, universal themes. A profound awareness of the past, and of the role of personal histories in the texture of our lives, have informed his work more or less from the beginning, and perhaps contributed to his decision to move to Ireland, where he has strong family connections, a few years ago.

This might make it all sound rather glum, which it isn't - part of the text he's written for the catalogue is actually very funny. His work is serious without being solemn, and it is matched by a certain gravitas in his understated personal manner. He is relaxed, even affable, but also, you soon realise, extremely focused and intense.

Corp is, in effect, a highly selective retrospective that crystallises one thematic concern. "I think quite early on I identified the body as the most significant element in the work," as he puts it. "There is a perception that you just don't paint the figure any more. It's been done, it's a given. But for me it has a centrality to it. To address the figure is to have a dialogue across time." There are several references in his catalogue text to the way people live their lives and vanish into oblivion. Those cited include someone who was presumably a relation in Mayo, Anthony, who died in 1920: "They buried him in the field and marked the place only within their memory so that now it is lost and forgotten." Another is Lowes Noble Rutter, a volunteer soldier who disappeared during the Battle of the Somme: "He disintegrated somewhere in the vicinity of Longeuval . . . It is almost as if he didn't exist." Then there is one of the so-called Bog People, the Bronze Age bodies, probably sacrificial victims, recovered in a remarkable state of preservation, most famously from a bog in Jutland. "I liked the fact that he was anonymous and obviously wasn't very important."

Perhaps the difference here is the symbolic resurrection of the figure. O'Donoghue draws an explicit parallel between this example of preservation and discovery, and the act of painting. "The process of painting is a process of disinterment and recovery. Putting on layers of paint is equivalent to the archaeologist, painstakingly excavating layer by layer, digging into the past." Previously he's talked of pushing paint back and forth across the canvas until he unearths an image. Even when the presence of the figure isn't obvious, it is usually there if you look carefully. In the Sleeper and Red Earth series, for example: "Sometimes the figure is literally buried in the painting, and the image reads more like a landscape, but the figure is there. And I think in the recent work it's there more explicitly."

The progress towards explicitness is a long, gradual process, and has to do with a question he asked himself. "Who is art for? I felt art had to function primarily on the level of feeling, rather than intellect. That's not to say it can't be intellectually engaging as well, but I think all great art has that confrontational, immediate quality. So I felt what I do should be fairly in-your-face. It should be that if someone comes and looks at it they can say: `Right, it's a figure, and go on from there.' "

We should go on, probably, to the issue of meaning, which is where history comes in. "I want to make history painting. Now, history painting is the most unfashionable kind of painting, because it's irrelevant to us. But I want to paint the history of ordinary events. We all wonder about the lives of our parents and grandparents, but what do those lives mean? I remember John Major as Prime Minister announcing that the Battle of the Somme was no longer going to be commemorated officially. It seemed to me to be an extraordinary thing to do, as if to say, we are no longer going to remember, we've nothing more to learn from this. Whenever I go somewhere, I tend to gravitate towards monuments, because they are repositories of the meaning of individual lives."

He draws another parallel, between the skin of the figure and the skin of the painting. As it happens, the surfaces of his paintings are extraordinary. Primarily a tonal painter, he likes to exploit different textural qualities in the space of a single work, using matt and glossy effects, thin glazes and thick accumulated masses of pigment side by side. But a speciality is a leathery, burnished finish, a dull gleam that resembles the patina of many years ageing. "The skin of the paint equates with the skin of the human form. That's partly why the story of Marsyas has been important." The mythical figure of Marsyas, rendered from an image of a classical sculpture, features in a vast drawing, Crossing the Rapido, in the exhibition. It comes from a postcard acquired by his father when he served with the British Army in Italy during the second World War. In recent years, O'Donoghue has been engaged in an ongoing project that amounts to a kind of posthumous biographical portrait of his father's life and experiences.

The Marsyas myth concerns a satyr whose virtuosity on the flute so fired the envy the lyre-playing Apollo that he challenged him to a musical contest, in which the winner would decide the fate of the loser. The muses inevitably judged in favour of Apollo, and the hapless Marsyas was tied to a pine tree and flayed alive.

The story became a popular subject for artists. Its precise meaning is unclear, but an allegorical reading interprets it as an account of spiritual rebirth, the vanquishing of Dionysian passion in favour of Apollonian rationality. Its appeal for O'Donoghue lies also in the explicit equation of skin with paint, first manifested in Titian's great painting of the subject. "At one stage I had a reproduction of the Titian and one of the bog figure photographs on the wall of the studio. But I never work directly from photographs, because memory is such an important part of what I do. Lucian Freud once said he always paints directly from life, in order to avoid the tyranny of memory. I'm all in favour of the tyranny of memory. Because I want to paint how it feels to be in a body, rather than its external appearance." This aspiration also relates to the scale of his work. "I've always liked to work big, because I think the figure should be at least comparable to human scale, and the space around it should be the equivalent of real space, not a fictitious space. And there's the desire to overwhelm the spectator, rather than offer something that is readily consumable." Hence the formidable presence of his work. Seeing it in reproduction doesn't prepare you for the real thing. It's not just the scale, there's also the worn, weather-beaten quality. "A finished painting is a history of its own terrain, and that's important to me, that the struggle is recorded there, the doubts, the bits that became awkward, the tensions of trying to resolve something."

He surveys the dark, sombre expanses of a Sleeper canvas with a rueful smile: "And it all started out so cheerfully."

Hughie O'Donoghue: Corp can be seen at IMMA from October 23rd to March 4th, 1999