RONALD REAGAN is evidently prepared to risk much higher inflation. He is calling for large tax cuts, beginning next January, that can only accelerate the inflationary trend. He justifies it by speaking emotionally of rising unemployment, and he demands "immediate action by Congress to reinvigorate the economy." Meanwhile, the Democrats, through clenched teeth, repeat that there will be no tax legislation this year. The Democrats find themselves the party of fiscal rigor and caution, while Mr. Reagan and the Republicans are prepared to run large dangers to get the country moving again.

Neither party, as you might imagine, is entirely happy with its new posture. The Carter administration is beginning to offer heavy hints that its opposition to tax cuts will expire on Dec. 31. Next year it would be prepared to contemplate tax legislation on a grand scale -- although, unlike Mr. Reagan, the president is not inclined to indicate the precise size or shape of the cuts.

Mr. Reagan has favored for some time a proposal to reduce individual income taxes 30 percent over three years. But there is a difference at least of degree between embracing the idea in principle and pushing unconditionally for legislation this summer to begin taking effect within six months. Further, Mr. Reagan adds, in the fourth year "these cuts must be made real and permanent" by indexing the tax brackets to the inflation rate. Mr. Reagan and his advisors deny that these cuts would make the inflation go faster. They would make the economy grow, Mr. Reagan argues, and he would end budget deficits by rooting out waste.

That argument lacks verisimilitude. The tax cuts and the inflationary risks are too specific and imminent; and references to reduced spending and the crusade against waste are too vague and remote. It's not as though Mr. Reagan were the first candidate, after all, to run on a promise to hold down the budget and go after waste.

But Mr. Reagan's tax plan at least serves the useful purpose of reminding voters that tax legislation in 1981 is all but certain, and the nature of that cut needs to be carefully debated. It's not at all clear that the right answer is the broad reduction in individual income tax rates that both parties have generally favored in the past.

Next January, when the new term begins, the American economy will present the president with uncomfortable choices. It's reasonable to assume that the recession will have touched bottom by then, but with slow recovery to follow. Suppose that unemployment in January is 8.5 percent and inflation, even at the bottom of the cycle, is still around 9 percent. To which of these numbers, both exceedingly high, should the president then give priority?

Mr. Reagan is saying that he would attack unemployment first, using the conventional method of cutting taxes, and take his chances on controlling inflation later in the recovery. As a matter of historical interest, we note that just four years ago, when the numbers were lower but the choice was exactly the same, Mr. Carter made the same decision.