The "new" work is called Insult to Injury. The exhibition in which it will be shown for the first time, at Modern Art Oxford, is called The Rape of Creativity. And then, in words likely to chill the staff of the Goya museum, he added: “I’ve brought some felt tips with me, so … ” So we've gone very systematically through the entire 80 etchings," continues Dinos, "and changed all the visible victims' heads to clowns' heads and puppies' heads." Jake cites Freud's Civilisation and Its Discontents. "Freud wrote that primary instincts are driven out of children for the sake of secondary gains. I may want to kill someone who is in my way on a bus, but it's better to ask them politely to move aside. Politeness gives me a secondary gain. That's what civilisation is like." So, in his art, is he trying to point out that beneath the veneer of civilisation we're all seething ids and repressed psychotics? "I don't think artists can do anything. An artist can only add shit to shit. Dinos once said, 'Our art is potty-training for adults.' He got that about right." The Chapman brothers are trying to help grown-ups be more civilised? "We're not here to help," he giggles. "We certainly don't care about moral instruction. Our interest in morality is not in being moralists, but in how morality works as a functional pacifier." Many of the brothers' works have their basis in the art of others, of particular inspiration are the etchings of Goya, which the Chapmans recreated in miniature in Disasters of War (1993) and as a life-size sculpture in Great Deeds Against the Dead (1994). Later, they directly appropriated original artwork, adding to and painting over the etchings of Goya, watercolors by Adolf Hitler, and 18 th and 19 th century oils.

They’ve taken Goya’s message – that war can’t be justified, that violence can’t be justified – and transformed it and built on it.” This question goes to the heart of their art, and explains a lot about those cuddly images of children and cutesy animals. The adult insistence that children are innocents corrupted by civilisation is a presumption the brothers want to subvert. "It's a will to believe, as Nietzsche would have put it. You can see it in Picasso, where he has this idea of getting rid of nasty adult instincts and seeing like a child. We don't believe in the idea of innocence, in the same way we don't believe in beauty in art. Celine [the French writer] said beauty is for poodles. He was right." Our interest is in what adults do to children and the image of innocence they project on to them," Jake continues. "Our thought about children is that they're pretty much psychotic, and that through sweets and other forms of coercion they are civilised." Spoken, I say, like a father. "Like a father of three," he says. (Dinos has two daughters.)Would Jake be happy for his kids, aged between three and 11, to see the show? "Of course. There are definitely things I wouldn't want them to see, and which I will protect them from seeing. But the things we've imagined in our art are anaemic compared with what kids imagine. I know it was a long time ago that we were kids [Jake was born in 1962, Dinos in 1966], but we were never innocents, were we?" Many of the works created by the Chapman Brothers’ are installations, or three dimensional environments with multiple facets and nuances. In light of this, we’re sharing a number of videos of their exhibitions, to offer a more complete sense of their art and aesthetic.The Chapman brothers have been working together since the early 1990s. Their art is deliberately confrontational, engaging with such inflammatory subjects and Nazism, the holocaust and religion, while it exploits an aesthetic of obscenity and horror. They appropriate elements from the history of art and philosophical and sociological theory to produce a body of work that derives much of its power from being politically and morally ambiguous, wilfully resisting straightforward interpretation. Significant exhibitions of their work include the Young British Artists (YBA) showcase exhibitions Brilliant! and Sensation. They were nominated for the annual Turner Prize in 2003 but lost out to Grayson Perry. Controversy is one thing but I think the seriousness of the work will go unnoticed. That’s the thing. One of the things that’s never discussed is the seriousness of the work.” But we live in ahistoric, depthless times, not least in art, and it's getting hard to be unimpressed by the sheer dedication of the Chapmans. The artists themselves claim they prefer to be despised as banal anti-humanists than praised piously as humanists. The language of praise we use for art is amazingly limited; if we like a work of art, we feel compelled to find depth, anger, moral fervour, spiritual truth - all the things the Chapmans claim to reject.

Aside from a shared art practice, each brother also has an extracurricular activity. Jake is, apparently, an enthusiastic writer of philosophical and critical texts; Dinos, meanwhile, is an unexpectedly accomplished recording artist. Last year saw his debut, Luftbobler, released on the Vinyl Factory label. A kind of techno album, Throbbing Gristle, Autechre and Aphex were all audible, luftbobbling around. It’s disarmingly good. Ultimately, she says, "What I think this work is all about is waking us up, so we don't sleepwalk our way through 21st Century life."Along with other members of the YBAs, the Chapmans's work was often gleefully tasteless and the brothers seemed to set out explore the topics most likely to cause offence, relishing the controversy they created and using it is as a means of self-promotion. This purposeful provocativeness led to accusations of childishness, and worse, that their work was immoral, and even illegal, and shouldn't be on display to the public.

They are the cleverest of the YBAs (Young British Artists)," says the art critic Matthew Collings. But Julian Stallabrass, lecturer in art history at the Courtauld Institute, has something far more withering to suggest. In his book High Art Lite: British Art in the Nineties, he talks about something that "looks like art but is not quite art, that acts as a substitute for art". The majority of artists purveying this, he writes, "have been content to play the well-remunerated role of court dwarf" while at the same time claiming they are engaged in some ironic exposure of the pretensions of old-style art. There wasn’t a whole lot of good art coming out of the UK in the nineties. The landscape was dominated by the YBAs – the Young British Artists, mostly graduates of the posh Goldsmiths college, all of them very comfortable with self-promotion and massive quantities of cocaine. Some of the art they made was striking, some of it was at best memorable, but real capital-A art was thin on the ground – unless it was being made by Jake and Dinos Chapman. Violet and white bursts of colour, the clown heads and puppy faces are astonishingly horrible. They are given life, personality, by some very acute drawing, and so it's not a collision but a collaboration, an assimilation, as they really do seem to belong in the pictures - one art historical antecedent is Max Ernst's collages in which 19th-century lithographs are reorganised into a convincing dream world. What the Chapmans have released is something nasty, psychotic and value-free; not so much a travesty of Goya as an extension of his despair. What they share with him is the most primitive and archaic and Catholic pessimism of his art - the sense not just of irrationality but something more tangible and diabolic. This is pure Freud; in a 1927 essay, Humour, he asserted that, “Humour has something liberating about it, but it also has something of grandeur and elevation… the ego refuses to be distressed by the provocations of reality, to let itself be compelled to suffer. It insists that it cannot be affected by the traumas of the external world; it shows, in fact, that such traumas are no more than occasions for it to gain pleasure.” As Dinos puts it, “If you can laugh at someone while they’re beating your head in, they’re not beating your head in.” His depictions of torture, rape, starvation and execution have long fascinated the British artists, informing their work and eventually leading them to inform his.Children who visit the gallery will get some protection from the Chapmans' more grotesque imaginings. "We're scatter-hanging the gallery," explains curator Selina Levinson, "so we can put the most upsetting images higher up." How does Jake feel about this cunning if sanitising hang? "In this case we have been relaxed about it. We have to be respectful of [the gallery's] thoughts about what the public and the trustees will find acceptable." Their large Hell landscapes, such as Hell (2000) and The Sum of All Evil (2012-13), are at once monumental in scale and minutely detailed. These apocalyptic landscapes, teeming with miniature figures, depict scenes of excessive brutality involving Nazi soldiers and, in more recent works, McDonald’s characters. The grotesque and often surreal violence of the scenes is offset by the overwhelming detail and painstaking labour evident in these and many of the Chapmans’s works. Of course, the Chapman Brothers didn't intend anything like that. Ready, as ever, with a dense rationalisation, Jake riposted: "Our intention was not in any way to trivialise the Holocaust." Rather, you see, it was a comment on the innate inadequacy of artistic responses to such genocide. "This is an event that's beyond representation. Using toy soldiers is a way of emphasising the impossibility of that. Here are these little figures that are totally incompatible with the pathos they're supposed to support."