QUEBEC'S SEPARATIST movement, as a crucial force in Canadian politics, is now ended. Its great advocate for the past 17 years, the Parti Quebecois, voted at its convention in Montreal last weekend to loosen fatally its commitment to the cause. It continues to favor an independant Quebec in principle, but it no longer intends to make independence the issue in the next provincial election. The vote was an acknowledgment that, among French Canadians, the impulse toward national independence has been fading fast. The party's membership is falling, and the surge of enthusiasm for sovereignty that carried it to power in Quebec nine years ago will no longer keep it there. The leadership of the Parti Quebecois decided that, if it wants to stay in office, it is going o have to set aside indefinitely any serious talk of separation.

This outcome of the separatist challenge is a triumph for Canadian political democracy. There was a time, in the middle 1970s, when it seemed that Canada was not far from splitting into two -- or perhaps more -- fragments. It was not easy to see the terms on which French-speaking and English- speaking Canadians might be reconciled. But the federal structure held.

One reason was the language law that the Parti Quebecois enacted, requiring much wider use of French in the province. That met the sharpest grievance of the French-speaking population -- that they frequently could not use their own language to earn their livings and carry out their business in a province in which they were the majority by nearly four to one. One consequence of that law was a shift by some businesses to Toronto, an unwelcome reminder of the economic costs that national independence might impose. But there's more to it than that.

In Quebec 25 years ago, the English-speaking minority was urban and educated -- the managerial and professional middle class. Quebec's working class, and the countryside, mostly spoke French, and among them the average level of education was well short of a high school diploma. But in the 1960s, after years of political passivity, French Canada began to press aggressively its claims to equality -- generating the separatist movement.

Now, nearly a generation later, the French language is far more widely used in business in Quebec. More important, the tremendous expansion of higher education has greatly increased opportunities for young French Canadians, and expanded the numbers of them in technical and managerial jobs. Language lines no longer follow so closely the boundaries of social and economic class. The separatists' failure as a party of political revolution owes much to their historic success as a party of social reform.