QUEBEC IS still a long way from dropping out of Canada. Before things go farther, there will be time for second thoughts and much more discussion. But clearly Quebec is now closer to secession than ever before.

The quarrel fundamentally revolves around civil rights and the differing definitions of them. The French-speaking Canadians of Quebec see themselves as a threatened island on a great continent dominated by English. To preserve their language and the traditions it carries, Quebec's leadership insists on rules that sometimes violate English-speaking Canadians' ideas of personal liberties. Quebec's prohibition of signs in English, including private businesses' signs, has taken on a large symbolic importance. The proposed constitutional amendments known as the Meech Lake Accord would have stated explicitly Quebec's right to preserve its special statusas a "distinct society," and Canada's PrimeMinister Brian Mulroney never entirely suc-ceeded in allaying anxieties that those amendments might conflict with the Canadian bill of rights.

He obtained a letter from several constitutional authorities reassuring Canadians that there was no infringement. But by that time he was knee-deep in demands from other groups demanding similar guarantees. If the constitution was to be amended to preserve the French language, how about further amendments to protect sexual equality, and the rights of aborigines and multi-culturalism in general?

In the end the Meech Lake deal collapsed on the refusal of two of the smallest provinces, Newfoundland and Manitoba, with 6 percent of the country's population between them, to ratify it. A rule of unanimity is always dangerous in a free society. But that was part of the agreement: the Meech Lake amendments would go into effect only if every province accepted them.

The initiative now lies with Quebec, whose middle-of-the-road premier, Robert Bourassa, is being pushed hard by the separatists. Many possibilities lie between the present federation and complete secession, and the conversation now seems to have begun exploring them.

Most Americans probably watch this process with some degree of regret, for this country's inclination runs strongly in favor of national unity. But American policy needs to remain absolutely neutral. As in certain marriages, differences that have become intractable over the years eventually justify divorce -- and no one outside the family can make that judgment. Characteristically, Canadians are meeting the possibility of secession with civility and a careful regard for due process.