Stage of Endarkenment

In the year of Homecoming, Mills has chosen to take the Scottish Enlightenment as a departure point. Getting a design duo on board who have been described as "William Morris on acid" perfectly encapsulates his curatorial vision: cheeky, ambitious, questioning and clever. The message is clear: don't expect a straightforward celebration of that remarkably fertile period in Scotland's history when science, philosophy and culture bloomed. Robert Burns barely gets a look-in.

"There's no automatic right for anyone, Burns or otherwise, to be in the programme," says Mills, ready to pounce on the subject as soon as it arises. In three years he has shown that the one thing we can expect from his programming is the unexpected. "If I'd decided we weren't going to play ball with Homecoming, that would be our decision. The independence of the Festival programme is important. I felt strongly that Burns would be on everyone's lips and it was important to recognise the many other poets and artists who lived and breathed in this country."

So Mills has instead commissioned the first staged production of Robert Henryson's The Testament Of Cresseid, by a neglected Scottish poet who inspired Shakespeare.

On the flipside is the universally renowned JM Barrie, though this Peter And Wendy comes with a kick, staged by the New York company Mabou Mines, who brought their surreal version of Ibsen's Dollhouse to EIF in 2007.

Mills' third programme is full of tensions between what we know about the Enlightenment and what we think we know, just as last year his theme of European borders stretched to include the Middle East. "It's about questioning, not closure," he says concisely. This is why a piece from Singapore on diasporas sits alongside generous amounts of Handel and Bach, and why the most bombastic homecoming comes in the shape of rebel Aberdonian choreographer Michael Clark.

"As much as everyone talks about Edinburgh being a serious and worthy place, under the surface bubbles all sorts of things that mean it's a good Festival city," continues Mills as we settle down in his office in the Hub. He looks relaxed in the midst of one of his busiest weeks – launching the Festival in Edinburgh, Glasgow and London before heading to Dublin and New York. He may be without his signature velvet coat, but his tongue remains as sharp as his tailoring. "It's about treating our culture in a robust way," he says of his decision to look beyond, around and askance at the Enlightenment, resulting in, for example, the world premiere of a play about the last woman to be executed for witchcraft in Scotland, written by Rona Munro and directed by the Traverse's Dominic Hill. This occurred just 18 years before Adam Smith and David Hume began their conversations about rationalism, humanity and civilisation.

"We're not simply saying, isn't Scotland great?" Mills says. "I think the mature thing to do, if one is focusing on Scottish culture, is to focus warts and all. I want to suggest that the thing we love most is the thing we should take most seriously, and the thing we take most seriously we should be prepared to critique as well as cuddle."

Mills, never one to miss an opportunity for intellectual wordplay, has termed the less illuminated side of the coin Endarkenment. "What I mean by Endarkenment is that every culture that is enlightened is always struggling out of a sense of darkness," he says. "Look, our science has never been more important than today and yet creationism flourishes in the bosom of the most scientifically advanced country on Earth."

Mills seems as fired up as ever, though he does ask me at one point: "Do you think people will go to this?" I wonder if the economic recession is casting a shadow. "I actually think it's easier," he argues. "If we're in a recession, we're forced to think about what we really care about. What I really care about is not making money. I am deeply sympathetic to people who have lost money. I think that's the pits. But broadly we need to stand up for the values that describe and define our humanity. We need to demand more of ourselves."

In any case, Mills has yet to see the impact of the recession with many companies losing grants. "Yes, yes, that's a joy just around the corner," he notes wryly. The Scottish Government is "doing everything it can in difficult circumstances", but he does feel more use could be made of EIF in the run-up to the 2012 Olympics. "I don't care how people come to this country and fall in love with it," he says. "Let's get them in the door, and use the Festival as a much more potent diplomatic tool than is currently being done."

In the midst of so much change across the festivals, from a guest director at the Book Festival to Intelligent Finance pulling its sponsorship of the comedy awards at the Fringe, EIF has remained the constant. Last year, as the box office debacle at the Fringe rolled on, EIF enjoyed its biggest ticket sales yet. "Yes, in a way we're the stable force," he laughs. "Having been the new boy on the block, three years in I'm one of the old timers. But if we think we can get away with being smart-arsed and brilliant at the expense of someone else, that's very shortsighted and profoundly ungenerous. It's interesting to remind ourselves how fragile all our lives are in Festival land." v

Edinburgh International Festival 2009, August 14 until September 6. Public booking opens April 4 (0131-473 2000) www.eif.co.uk