Jacques Parizeau is thinking of us again. The cuddly irredentist is pressing for a referendum on Quebec's sovereignty by next year - not for his sake, as he so often maintains, but for ours. ''This uncertainty has to end,'' he said this week. ''It's extremely damaging . . . both for Quebecers and for the whole Canadian climate.''

But Parizeau has not gone completely soft on Canada. In the same appearance, he vowed that a sovereign Quebec would keep using the C$, and there's nothing we can do to stop them. ''All it would take is to declare the C$ legal tender in Quebec and, voila, it's done.'' Chortle, chortle.

True. In fact, it needn't even take that much effort. The US$ circulates as the unofficial currency in many Third World countries, with or without their governments' approval. The only use in calling something legal tender is to prohibit the circulation of other currencies. All the same, it's unclear why Parizeau should be so keen on aping their example.

Certainly Quebec would benefit, both in convenience and credibility, from retaining what is becoming the hardest currency in the group of seven industrialized countries (assuming it remained so after separation). Business would be spared the transitory upheaval of changing the denomination of prices at home, and the transaction costs thereafter of exchanging currencies at the border.

A newly minted Quebec currency, moreover, would be a frail vessel indeed to push out into the storms of international investor sentiment. The price would likely be a period of ferociously high interest rates until the new government had established its anti-inflationary credentials. But if security were all Quebec wanted, it would stay in the country.

Of course, Quebec could tie its currency - the Frontenac? - to the dollar, Canadian or American, by means of a fixed exchange rate. In the long run, this would ensure that Quebec would have to lock step with the target country's monetary policy. Either this arrangement would be permanent, or it would not. If it were not, it would be no help in convincing investors Quebec would not eventually lean to inflation. If it were permanent, it would be far easier, and equal in effect, just to keep the C$. There are costs, however, both economic and political, to this.

Economically, it would mean Quebec could not devalue its currency as the terms of trade demanded. Devaluation is a false cure, if carried out by means of inflation. The foreign exchange rate falls, but domestic prices rise, so any depreciation is nominal, not real. But there are circumstances in which the market itself will demand that the currency rise or fall, to balance trade and capital flows.

In Quebec's case, the brunt of adjustment would have to be borne by domestic, rather than external, prices. That's why Parizeau himself used to argue against it. Indeed, it is an open question, even among economists who are not plotting to dismember the country, whether Canada, with the diversity of its regional economies, constitutes an ''optimal currency area.''

Worse, Quebec would have no control whatsoever over its own money supply. This is one way, to be sure, of guaranteeing the independence of monetary policy from political control. As a matter of pure economics, that might be desirable, on balance. But it hardly befits a sovereign nation. The whole point of sovereignty, surely, is to seize control of the levers of government. If the single most important policy instrument is to be left out, it rather spoils the fun. Why, it's almost - what's the word? - humiliating.

In fact, it would leave Quebec with less sway over the central bank than it has now, and far less than it is likely to have under a revamped Bank of Canada. As things stand, the Quebec vote is the decisive factor in electing the federal government, which in turn chooses the governor of the Bank of Canada (and exercises ultimate control over policy), who is himself unusually powerful within the bank - Alan Greenspan would like John Crow's authority.

There is increasing support for the provinces to be given a hand in selecting the bank's directors, who would be given real decision-making power. Even the impeccably hard-money C.D. Howe Institute endorses the idea, with qualifications. There is simply no prospect - zero, nada, rien - of an independent Quebec being given a seat on the bank's board, let alone the equal representation of sovereigntist fantasy.

So if Parizeau means what he says, the net effect of declaring independence, in this as in other areas, would be to reduce Quebec's autonomy, not to increase it. And Jacques thinks Don Getty's dumb.