Paris — On his first official visit to Corsica this week, French President Francois Mitterrand discovered firsthand why the island remains racked by separatist violence.
In general, Corsicans welcomed Mr. Mitterrand, and major political leaders expressed satisfaction with his new autonomy law and recent proposals for stimulating economic development.
But to protect the President from an attack by the outlawed Corsican National Liberation Front (FNLC), 2,500 policemen were flown in from the mainland.
Police estimate that the FNLC has only about 200 members. But last year it committed more than 800 bombings, and has claimed responsibility for 300 this year.
The bombings are not meant to kill, only to frighten ''continentals,'' as Corsicans call mainland-born French, into leaving the island. If a resident ''continental'' refuses to pay a ''revolutionary'' tax of about $450 to the separatists, while he is away he risks having his car, his shop, or his house blown up.
Explosions have become a part of daily life on the island. A few teachers have been scared into leaving, but businessmen with property on the island have been more hesitant to go. They quietly pay the FNLC's tax.
To end this uncomfortable situation, Mr. Mitterrand originally made concessions. Just after his election, he granted amnesty to some jailed separatists. And last year, he accorded Corsica its first popularly elected assembly, with wide-ranging powers, especially in education and planning.
But the reforms have not satisfied the FNLC. They claim such moves merely disguise continued mainland ''colonization'' of Corsica. Feeding on resentment toward ''continentals,'' who own much of the best land and businesses on the island, and on a code of silence that protects rebels, they escalated their separatist violence.
Mitterrand responded in January by outlawing the FNLC and appointing a well-known policeman, Robert Broussard, to crush the group. Mr. Broussard has made some arrests, but has been unable to end the violence.
Recently, he has taken a new tack - trying to discredit the separatists by attempting to link them with the Mafia. But this has not prompted mass informing against the separatists.
Mr. Broussard's failure to break the traditional law of silence shows how locked in their ways the island's 240,000 residents remain. Feudal-like clans continue to dominate political life, and Corsica remains an agrarian economy with a per capita income 30 percent lower than the mainland's.
Polls show a clear majority of Corsicans want to remain part of France. In last year's regional elections, autonomists won only about 10 percent of the vote. But presidential visits, it seems, are not enough to quash the destructive will of a violent minority.