Reading Henry James' short story "The Private Life" has made me wonder whether a constitutional convention might not be a good idea after all.

A leading character in that 19th-century tale is Lord Mellifont -- the most charming man in Great Britain. He is handsome, accomplished, self-disciplined, and affects to love everybody. He has a wonderful smile, is altruistic and sincere, and is universally regarded as a good man. He has the knack of saying just the right thing, no matter where he might happen to be, and, above all, excels in the ability to please -- and thereby to dominate -- whatever group he's with.

Such energetic assiduity, James surmises, must take a lot out of the man, and in the beginning of the story he occupies himself with the question of "what really became of him when no eye could see. He rested, presumably; but what form of rest could repair such a plenitude of presence?"

He finds the answer from an actress who has gone out with Lord Mellifont gathering mountain wildflowers. She, being obliged to return to the lodge, leaves the lord alone on a huge hillside. And when she remembers one more thing she had to say to him, and turns back -- no one is there. Nor was there any place he could have gone to. So Mellifont, it seems, takes his rest by poof -- vanishing! -- ceasing to exist until the time comes for him to be in company again. His life, then, is a series of appearances, and is summed up by James like this: "He's there from the moment he knows somebody else is." His wife knows this, and the servants do, and so do those who have been around him long enough. But nobody ever speaks of this thing -- possibly because of the disgrace associated with such an intermittent existence.

It is through the lens of this story that I came to view the complaining around town that has sprung up in the wake of President Carter's two recent speeches: the one on May 26, in which he told the men of the carrier Nimitz that he was gong to increase defense spending; and the one on May 27, in which he told city executives that defense spending had to be cut. Because of the discontinuity in these, people of many political persuasions have been calling Carter a hypocrite.

But isn't that taking a too-optimistic view of the matter? Because if the republic's chief trouble is that we have got a hypocrite in the highest office, all that needs to be done to establish felicity is to vote him out and elect somebody who isn't.

For my part, however, I doubt that Carter is any hypocrite -- and this, in spite of those two contradictory speeches, and the many other clashing announcements that come out of the White House as joltingly opposed as the Redskins and the Cowboys. Because this would imply some sort of crouching, malefic scheming on his part, in highly conscious hours that intervene between pronouncement No. 1 and pronouncement No. 2. But does that interval take place? What really happens, one suspects, is the more innocent process -- which is to say, a pleasing speech, followed by an interval of darkness, followed by another pleasing speech.

This, perhaps, is just politics as usual, and requires no Henry James to make it understood. Nor does it imply that Carter is shallow. After all, Lord Mellifont, in James' story, isn't shallow, and neither is he a hypocrite: However, in some meaningful sense, he is just not there between his public manifestations. And in his case, such discontinuity suggests the lack of a private self. But in the case of a United States president, it implies discontinuity of policy and gives the world a disturbing sense of vacuity -- the lack of any national self at all.

Growling at Carter about this, however, may prove costly sport, especially since his being president in the first place is not entirely his fault. After all, that office, as institutionalized in our Constitution, removes from its possessor any obligation to be there, in the sense of being responsive to those of us who elected him. And it seems to set forward an intermittent socially graceful pleasingness as the highest qualification for the highest office. Thus, since the Constitution itself, with its notion of a remote executive, encourages Mellifont to come forward, it is the Constitution, in part, that suggests an answer to the question most often heard around town: "Why are men like these our only choices?"

Could it be that these are the sort of men the ground rules attract? For, just as some folks get married to end their sex lives, others run for president to end their political lives -- if by that one means the sort of meaty, human give-and-take that obliges one to be consistent.

Our chief executives, by law, are lifted high above all that: are searchingly questioned by no one, are never called to the bar of reason, and need only pop up now and again saying what seems most pleasant at the time -- a system ill-suited to a democracy. And, while that may have worked in the old days, when oceans were wide and penalties correspondingly low, it does not work now. If we put the national welfare over the sacredness of old documents, we would do well to look to it. In recent years, a series of Mellifont-like presidents have led us, charmingly, into futile catastrophes and avoidable humiliation. And this has caused some of us to wonder whether a parliamentary system, in which the chief executive is subject to continuous scrutiny, might not work better. In that way, at least, we could peek every now and then to make sure somebody is there.