Sometimes I envision an imaginary first man on earth. I see him rising, dusting himself off and then mounting a log to see what his new world looks like. About to jump off the log, he pauses. Knowing nothing of gravity, having never seen another person jump, he might well think that a leap would carry him for miles -- like on the moon. Eventually he jumps and immediately comes down. A lesson has been learned. From now on, he will assume that when he jumps he will come down -- what happened in the past will happen in the future. History is a great teacher. It is also a great deceiver.

I thought of that man and of history around the time Gary Hart withdrew from the presidential race. The cause of that debacle was said to be his relationship with part-time actress Donna Rice, with whom he spent part of a weekend in Washington. Everyone agreed that Hart had been done in by poor judgment and, of course, lust. In the popular imagination, he had been seduced by a woman. Actually, he had been seduced by history.

This was irony on an epic, even Grecian, scale -- a kind of intellectual jujitsu in which what you know is used, like your own weight, against you. In Hart's case, it was his knowledge of history. Probably no contemporary American political figure is as keen and determined a student of our history.

To a degree, it was this knowledge that made Hart the Democratic front- runner. He recognized that America was approaching a generational watershed. John F. Kennedy's generational triumph happened 27 years ago. It was time for a new generation to assert itself. He would be its leader.

But if history informs, it also blinds. The challenge to the press that Hart so casually uttered -- "If anybody wants to put a tail on me, go ahead. They'd be very bored" -- appeared the same day that The Miami Herald story on Rice appeared, but it had been tossed off with the confidence of a man who knew he would never be taken up on it. After all, history said so. Not since Grover Cleveland had a presidential candidate's sex life been an issue.

Indeed, a maturing American press, craving respectability, had looked the other way when Franklin D. Roosevelt's presidential train stopped in New Jersey so his mistress, Lucy Rutherford Mercer, could board. And Kennedy, whom Hart studied and emulated, had carried on in the White House. Official Washington, that sewing circle of politicians, journalists and hostesses, even knew the names of some of the women but kept the information to themselves. This was not the people's business.

There was ample reason for Hart to conclude that the press would never break its self-imposed taboo. His only bad judgment was to rely on history, on what he knew about how the system worked. Less sophisticated politicians might have feared a voyeuristic press. Not Hart. He knew better.

What happened to Hart also happened to Richard Nixon. Once again, here was a student of history, particularly of the presidency. Nixon, too, was seduced by his own knowledge -- by what history said was and was not possible. What was not possible was that the judiciary would compel a president to surrender his diary, even in the form of tape recordings. It simply had never happened.

A president who knew something about history could comfortably think that only he could avail himself of his private tapes. He could use them to rebut the charges against him. It was inconceivable that they could fall into the hands of his political enemies. Yet that's what happened. And while in hindsight Nixon may appear incredibly dumb for not destroying the evidence against him, he was in fact doing the logical thing. He had history on his side.

Ironically, the same knowledge and experience that ultimately brought down Nixon also handicapped his "enemies," the press. The more a journalist knew about American politics, the harder it was to believe that the Watergate burglary could be connected to the president of the United States. This was not just another political dirty trick -- not like tying up an opponent's phones. This was a criminal act and one that seemed to make no sense. Why burglarize the Watergate offices of the Democratic National Committee? What could be there, as opposed to George McGovern's campaign headquarters? A burglary was an act of desperation, and Nixon, in June of 1972, had no reason to be desperate. McGovern was almost certain to be the Democratic candidate in November, and Nixon was almost certain to beat him.

For these reasons, some pretty canny political journalists minimized the Watergate story. It took two local reporters, Bob Woodward and Carl Bernstein, to keep at it. Unencumbered by any first-hand knowledge of campaign politics, not yet admitted to the inner circle of Washington know-it-alls, they naively pursued a political story as a police story -- and helped bring down a president.

Hegel referred to the "cunning of reason" -- his synonym for history. It can be studied. But the knowledge gained from it is limited when predicting the future. Nixon relied on it, and it let him down. Hart did the same. One man was seduced by power, the other by lust, but they were betrayed by their knowledge. They assumed the past was prologue. It was not. It was just the past. ::