THE VEHEMENT quarrels breaking out over money inside the Reagan administration are not only entertaining but instructive as well. The budget deficit, it now appears, is real and is going to persist for quite a while. In response, some of the most faithful of the administration's conservative idealists have begun to fear that the Reagan revolution is going to get lost in the petty distractions of budget arithmetic. They are dismayed to see decisions being driven by the struggle to get the deficit down. Would it not be nobler, they ask, to rise above mere bookkeeping and move national policy grandly to the right despite it?

You could call it high-budget conservatism, a new phase of the crusade being encouraged by various White House and other enthusiasts. Among the current list of conservative causes, a great many would carry substantial costs. Generally they are in the form of highly focused tax breaks designed to induce you to do what a good conservative administration would want you to do. These proposals come from people who favor letting free markets work unimpeded but, like other people, they are not opposed to tilting those free-market choices, through the tax system, in the direction of reason and virtue. As usual, reason and virtue do not come cheaply.

For example, President Reagan remains warmly committed to tuition tax credits. That means federal aid to private schools. And then there are the tax incentives to encourage investment and development in enterprise zones, in depressed areas like the abandoned industrial neighborhoods of big cities. It's the administration's answer to urban renewal, different but not necessarily cheaper.

Since the administration's strategy to increase private savings hasn't worked, there is now talk of providing more encouragement through larger tax exemptions for interest paid on savings. Interest is a huge component of personal income, nearly equal to Social Security and all the other government transfer payments put together. To reduce income taxes on interest would be another very substantial contribution to the deficit, in the wrong direction.

Perhaps some of these ideas will seem implausible even to readers who consider themselves conservatives. But running through them is a message that is going to get more explicit and seductive as the months pass. It suggests that since the deficit is already so large, and the efforts to reduce it so futile, why bother? Why not ignore it and have a little fun? If that insidious idea begins to pick up momentum, it will sharply increase the threat of rising inflation and much higher interest rates -- a threat that is, in truth, already quite large enough.