Leading article: A festival of discovery

Many arts events claim to be the biggest and best in the world. The Edinburgh Festival, which gets under way this weekend with the first Fringe events, has one of the better claims. Four weeks of theatre, music, comedy, film, dance, literature and children's events in one of the most beautiful and, crucially, walkable cities in the world takes some beating.

It is also an eminently sociable event, with audiences and performers mingling in late-night bars in a way which rarely happens elsewhere, and the city taking on a hedonistic feel that is in the starkest contrast to the other 48 weeks of the year.

But artistically, both the official Festival and the Fringe need clearer definition. One of the key figures on the Fringe this week accused the main Festival of being too rigid and backward looking. Certainly, there is a need for the International Festival to do more to offer the best in the world. The likes of Peter Brook, the Berlin Phil, the Kirov Ballet, should grace the Edinburgh Festival. Too often, the programming slips from premier league to first division. Genuine experimentation must also be part of the official Festival mix.

But the Fringe must look to itself as well as criticising its older, more conservative sibling. The Fringe attracts a younger, less affluent audience than the official Festival, and it does not always appear to have their interests in mind. Prices for 60-minute performances are increasingly too high for a festival in which audiences expect to see two or three shows a night. Comedians are less likely to be new talent in search of fame, and more likely to be established TV figures trying out their new routine. Theatrical innovation has been thin on the ground in recent years. It was the Fringe, after all, that once gave us Tom Stoppard's first play. It will be a nice surprise if this year's Fringe comes up with a new, serious playwriting talent to set the world alight.

Edinburgh in August is about three things: excellence, discovery and fun. The last is guaranteed. But excellence and discovery cannot be so easily promised when there continues the inexorable takeover of the Fringe by established TV comedy acts and of the main Festival by the safe and solid rather than the challenging and the world class. Even the biggest and best arts festival in the world needs to avoid complacency.