Music stirs the most elemental passions. It has roused men to battle, celebrated victories, annointed kings and accompanied the dead into the grave. Some of the greatest music has been inspired by sweeping historical events: Beethoven was deeply influenced by Napoleon's victories, Shostakovich voiced the courage and defiance of his fellow Russians starving in the besieged city of Leningrad. In more recent times, music has been harnessed to global events and campaigns to huge effect. Live Aid did - and still does - more to make millions aware of starvation in Ethiopia than any speech. Rostropovich used his cello as a beacon of freedom, playing beside the Berlin Wall. And who can forget the emotional triumph of Bernstein conducting Beethoven's Ode to Joy amid the wreckage of the Wall?

Nevertheless, the concert given in South Ossetia yesterday by Valery Gergiev, the principal guest conductor of the London Symphony Orchestra, will provoke the criticism that as a brilliant conductor of world-class stature, he has demeaned his talents. By putting them at the service of a propaganda celebration of Russian military might, he has crossed the line that ought to separate art from politics, beauty from brutality. He has made his music an instrument of Russian foreign policy, conducting in the name of conquest.

No one should question the sincerity of Gergiev's feelings. He is himself Ossetian. His wife and children still live in the region. He is also a close friend of Vladimir Putin, and may share some of the Russian Prime Minister's politics. He has not made Russian nationalism a leitmotiv of his music. But he is entitled, as is every artist, to his views, and to express them when he sees fit.

Gergiev shares a long tradition of musicians who have championed causes in which they believe, often controversially and at some personal cost. Yehudi Menuhin, whose concerts for Belsen's victims were widely applauded, was criticised by many, especially fellow Jews, for his initiative after the Second World War in proffering the hand of reconciliaton to Wilhelm Furtwängler, the German conductor who continued to play for the Nazis throughout the war. Daniel Barenboim similarly has angered some Israelis by playing concerts in Ramallah and for teaming up with Edward Said, the Palestinian critic of Israel, to found a Palestinian-Israeli orchestra.

The artist - and, therefore, the art - can never be entirely divorced from his or her opinions. The question is whether the artist's cause is just. This is always a matter of judgment. Were Sir Simon Rattle to take the Berlin Philharmonic to Kabul to play for those fighting the Taleban, few in the West would complain. It would not be the same in the Muslim world. In Gergiev's case, he has applied his talents in the name of what this newspaper deems an unwarranted act of war, an imperialist urge resulting in a military intervention. Gergiev has associated his musical brilliance with Moscow's military bullying.

But whatever the criticism, which this newspaper shares, of the Russian actions to which Gergiev has lent his support, it is important to realise that in a Western society this conductor can still play freely, despite his controversial visit. Defiance in Mr Putin's Russia, as in the Soviet Union, results in ostracism. It should not do so here.