TODAY IS the day they are commemorating the president's first six months in office, so we will join the fun. The administration thus far has shown these defining characteristics. 1) It is very much, perhaps distinctively, the creature of its leader, a president who is relaxed, a delegator: he is clearly comfortable in the job and not afraid of limiting his hourly, minutiae-bound involvement in it, and with this approach, paradoxically, he has strengthened his capacity to govern forcefully, to make things happen. 2) The administration is reacting with vast energy and commitment and self-confidence to its own sense of mission and that of its basic constituents, and this accounts for both its achievements and its shortcomings.

At the time of the president's election, there was in this country a general consensus, much larger than that reflected in the actual Reagan vote, for correcting and reversing a lot of trends associated with Democratic liberalism and establishment dogma in both domestic and foreign affairs. The question is whether the administration, in responding to this mandate, is not in certain areas being as extravagant and doctrinaire and undiscriminating itself as were the perpetrators of all those various excesses it is trying to cure.

Mr. Reagan has shown himself as skilled at the politics of making a government perform as he was at the politics of getting elected. Witness the unexpected accomplishments of his ambitious plans for federal budget cuts. The president and David Stockman and company knew they had to move very fast, concentrate all attention on this issue, grease and/or contend with Congress where and as necessary and let nothing take precedence over their early assault. It worked, at least insofar as budget cuts beyond anything previously thought possible were made. One part of the downside of this strategy has been that preoccupation with the budget battle has either caused or been used as a justification for neglect of other business.

We will be frank with you: we couldn't be more pleased that some of this business has been neglected. On a variety of civil liberties, civil rights and so-called "social" issues (all political issues are social, even the ones that seem to be about geology), the administration has yet to get its act together or issue promised policy statements. We can wait. Congress and the Court are already doing plenty in this realm that strikes us as ranging from mischievous to miserable, and we do not have enormous faith in this administration as a prospective rescuer of the situation.

The general vacuum that has resulted from all the highly trained attention on the economic program has been filled or not filled as you would expect according to the caliber of the people doing other jobs. For example, although the administration's overall deregulation campaign has yet to be brought to fruition at Transportation, some practical, if difficult, decisions have been made, while at the Energy Department -- and in fact in the whole field of energy policy or lack thereof -- the indifference and inaction have been marked. Likewise, the president's concentration and that of his top aides on getting that economic package through must be accounted one reason that within his national security group there has been such institutional dishevelment and noisy political discord.

But the concentration on that package is not just a cause (of certain other behavior). It is also an effect, a result, the end-product of a kind of zeal that has led the administration to override everything in its way. Some things deserved to be overridden. But others didn't, including certain values and commitments a federal government and a decent society should preserve. And so, as it awaits the general benefits promised by a dubious economic theory, it has put at risk -- by some of its welfare, Social Security and other federal domestic program cuts -- the minimal well-being of persons who are already at the bottom of the economic heap. And when you combine this with the bias of the Reagan tax program toward the rich and the evangelical and somewhat careless way in which the overhaul of certain policies affecting blacks is being approached, it takes on an aspect of coldness and indifference probably utterly at odds with what the president intends.

This all-or-nothing attitude is evident as well, of course, in Mr. Watt's Interior Department and to some extent in the administration's attempt to reconstruct foreign and defense policy on some basis less wishy-washy and inconclusive than that it inherited. But the commitment, again, often seems without its inner discriminations -- on arms transfers, and nuclear non-proliferation, to take two examples. We are among those who believe much of the administration's reaction and that of the public against prevailing national security nostrums was justified. But we often get the sense of being in the presence of an overreaction, a self-certainty and slavishness to doctrine that, whether in the human rights field or that of Third World dealings or arms control, could propel the government from sensible actions to reckless exercises in theoretical point-proving.

It will take much time to test out the validity of Mr. Reagan's foreign policy assumptions (especially concerning U.S.-Soviet relations) and also that of his economic bet. And it takes more than six months to tell how much of an administration's early conduct is here to stay for the whole four years. So everything is in doubt. And this is above all true of the big question: namely, whether this administration will be a four-year reaction -- a fluke -- impelling a wayward political establishment to correct its course, or whether it marks the beginning of something solid and big. But we will say two things with certainty. One is that if the administration overreaches -- as it now seems inclined to -- in its attempt to counter the defects of the Democratic past, it will hand Jimmy Carter his best revenge. The other is that this administration would be enormously improved by the existence of a strong and intelligent and coherent Democratic opposition. But that is nowhere to be seen, and it is one thing, even in a political culture that holds presidents accountable for everything from heavy rainfall to baseball losses, that can't be blamed on Ronald Reagan.