THE ONLY surprising thing about President Reagan's budget for 1983 is that it contains so few surprises. It is a direct application of all his long-held ideas about federal spending: he has kept the faith with his earliest supporters, and with all his promises on that subject.

The next question is whether it's a political virtue to keep the faith with ideas that aren't working and with promises that are getting the country into trouble. This budget ignores all the lessons of the past year's experience as though it had never occurred. As the instrument of the president's broader economic strategy, it is dismaying in its flat refusal to recognize the dangerous inconsistency between the big deficits, pushing in one direction, and the tight monetary policy that pulls in precisely the opposite.

Mr. Reagan proposes another round of reductions in the social programs, on the same scale as last year's. Once again, the most justified cuts are not those most likely actually to be enacted. To make another large cut in food stamps now would be profoundly wrong as social policy, but as a political reality it is more likely to be passed into law than, say, the proposal to hold down the rate at which physicians' fees rise under Medicare. Generally speaking, the social programs that serve mainly the middle class would continue to receive very careful, not to say gingerly, treatment under this budget, while those serving the really poor would not.

The size of the deficit is obviously a matter of the most acute embarrassment to the administration-- and for good reason. Last year's deficit was $58 billion, and as recently as last summer this year's was supposed to be $43 billion. Now the administration says that it's going to be $99 billion. Next year's deficit, again according to the administration, will be slightly lower, at $92 billion. You would be wise to treat that last figure with some considerable skepticism. If you make two adjustments--one for the spending cuts that Congress clearly isn't going to entertain, and one for the excessively optimistic economic forecast--you will arrive at a more likely figure somewhere around $135 billion. The deficit is getting larger not only in terms of dollars, but also in relation to the gross national product, the nation's total output.

Mr. Reagan is correct in saying that the current state of the economy is the result of many years' bad habits. For more than a decade, most of the people in this country have demanded more from their government--especially more personal benefits--than most people were willing to pay for. Under President Reagan's leadership, the scale of the benefits is slowly declining, but the tolerance for the taxes to pay for them is declining much faster. The result is more of the same, with public demands for many kinds of protection far outbalancing any public sense of responsibility to contribute to the common good. The Reagan budget reflects a failure of proportion that is not confined to the purely fiscal. Nor is it likely to be remedied as long as the president, his administration and most of the country continue to evade the true magnitude of the shortfall.