LORD Louis Mountbatten died of the Ulster disease. The time bomb that blew up his boat also killed his 14-year-old grandson. They are among the latest victims of the disease, along with the British soldiers who were killed yesterday by another bomb, in a separate incident, not far away. As usual, it is the Provisional IRA that claims what it calls credit -- although credit is not a term that most people would use in connection with planting bombs, the most indiscriminate and least courageous methods of killing.

Lord Mountbatten was one of the genuine heroes of World War II, and a man of great political skill. He was also a cousin of Queen Elizabeth II. By taking him as a target, the IRA clearly intended a victim of large symbolic meaning to his country. The bombing campaign seems lately to be aiming more closely at public figures.

If you were to ask the bombers what they were trying to accomplish, they would reply that they seek to drive the British out of Northern Ireland and to unite it with the Irish Republic to the south. The IRA clings, as an article of faith, to the thought that Bitain keeps troops in Northern Ireland for the sole purpose of oppressing and harassing the Irish people. That logic conveniently overlooks the fact, hard as rock, that two-thirds of Ulster's population are Protestants, obedient to a leadership that remains deeply hostile to the Irish Republic. To the IRA's crazy zeal, the Ulster Protestants respond with a sullen and obdurate determination to give up nothing. If the Protestant community in Ulster had been willing to grant the Catholic minority equal political rights a dozen years ago, this whole decade of guerrilla warfare, with its nearly 2,000 deaths, would never have happened.

But Lord Mountbatten is a peculiarly ironic target for a movement like the IRA that sees itself as the enemy of imperialism. The Indian government yesterday declared seven days of state mourning in memory of the man who presided over its transition from a British colony to an independent nation. Lord Mountbatten was the last viceroy of India and the first governor general. He embodied an enlightened solution to imperial crisis.

In Ulster, by way of contrast, the antagonists seem almost to welcome the idea of stalemate. Britain has showed a degree of resentment at the unrequested advice that it has recently been getting from American politicians. But it is necessary to say that this transatlantic nudging springs from a deep anxiety in this country that the British government has abandoned all political initiatives as equally hopeless. It seems to have decided grimly to leave the army to do what it can in Ulster, while the rest of Britain gets on to more rewarding things. Lord Mountbatten and his generation brought democratic self-government to India. No one has yet managed to do as much for the violent and unhappy province of Ulster.