MEANWHILE, WE HAVE an authentic and unvarnished description of President Reagan's own visceral convictions about the budget -- in the transcript of an interview with him that The Washington Times published on Thursday. Since the daily reports on the internal budget debate are being filtered through his staff, it's useful to keep in mind the distinction between the publicly expressed views of the White House as an institution and the personal opinions of its principal tenant. In the end, it is safe to say, these personal views are likely to be controlling.

Through the campaign and since, Mr. Reagan has become increasingly adamant in his opposition to any tax increase. Defending the 1981 tax cut, the great political triumph of his first term, is clearly his top priority in economic policy. What about the budget deficit? The Washington Times's editors asked him that question, and he replied: "The deficit is a result. What you have to get at is the problem, and that is government is spending too much and it's spending too big a share of the private sector." So the second-term priority is to get spending down. It's high public spending that causes trouble, he believes -- not, he implies, the deficit itself.

Parenthetically, our own view is precisely the opposite -- that the deficits will make enormous trouble for this country if they continue to run unchecked. But our purpose here is to trace out the president's logic, not to argue with it.

The Washington Times's interview makes it quite plain that Mr. Reagan continues to hope that economic growth will take care of the deficit. If you can just slow down the rate at which spending rises, he said, you can still cover real needs plus inflation -- and eventually, even if "you can't exactly foretell the day," the growth of the economy will generate the revenues to balance the budget. There is hardly anybody outside the administration -- or, for that matter, inside it -- who has looked carefully at the numbers and who agrees. But, once again, what counts here is Mr. Reagan's view.

As for economists, including his own, Mr. Reagan has quite clearly developed a contemptuous disregard for the breed. Most of them have been saying for three years that those big deficits are pushing the country toward financial disaster. Instead, there's been a marvelous boom that re- elected him in a gigantic victory. The president and the political people around him have simply tuned out the economists.

Deficit trouble ahead? He'll believe it when he sees it. In the meantime, he'll hold firm on taxes, do what he can on spending and, in his usual cheerful and confident manner, hope for the best.