Henry Jackson, who has represented the great state of Washington in the Senate for 30 years, has also been nearly every president's unavailable first pick for secretary of defense. He is known as a strong defense man and no sentimentalist. He is, by reputation at least, the Democratic superhawk.

But reputations are often misleading, and Jackson's reputation is too schematic to fit the interesting contours of his views on weapons and war.

He is among the few students of defense who are neither shocked nor disconcerted by the sudden popular discovery of the nuclear menace.

When he met with reporters for breakfast this week, the senator handed out a thick packet of documents showing a long, persistent record of warning about nuclear weapons. In 1953, he told the Senate: "If the road before us continues without turning, the future promises us at best a world living in fear of annihilation."

There has been no turning in the road. The future is here. The same sentiments, appropriately updated, are echoed in Jackson's recent Senate resolution calling for a conservative variant of the nuclear "freeze." When he introduced the resolution, with Sen. John Warner of Virginia as co-sponsor, some smug young people wrote the senator off as a man on a White House errand, seeking to ease the growing pressure on President Reagan.

That idea he indignantly rejects. "It was worked out between Dorothy Fosdick (his national security staff assistant) and myself and no one else," he says.

In fact, in the Jackson file distributed to reporters the other morning, there is a letter to the president dated March 1981 urging "a bold and imaginative proposal for serious arms reductions . . . (at) sharply reduced levels."

If anyone could say why Jackson's authoritative advice has gone so long unheeded, then we might have a useful key to the nuclear dilemma. The problem, after all, has changed only in scale since Winston Churchill defined it vividly three decades ago. The explosion of a Soviet hydrogen bomb, Churchill said, meant that "safety has become the sturdy child of terror." The child has grown adolescent, and less sturdy.

One factor that has thwarted Jackson and others is the tendency of weapons technology to outrun political calculation. For instance, the "mirv-ing" of missiles (placing "independently targetable" warheads on them) and the cruise missile (an updated buzz-bomb with a vastly improved guidance system) are destabilizng by-blows of technology, not subjected to timely forethought of their political effect.

In fact, every effort to grapple with arms technology after the fact seems to yield only greater complexity. Arms control has become the tax reform of national security, as beneficial to arms-control intellectuals as tax-reform bills are to accountants and lawyers and, too often, to few others.

That, presumably, is why Jackson's thoughts are turning to a new investment of energy in the neglected political and institutional checks against nuclear war. The United States and the Soviet Union, he thinks, should establish by negotiation a "joint command post" to exchange critical information and avoid miscalculation. He calls it a "conception in search of an architect." The architect would certainly need to wring more candor and information out from the Russians than they usually provide, as well as allay allied suspicion of any superpower club that seems to monitor the destiny of others without consultation.

But Jackson's "command post" idea does recognize that political instability and miscalculation are more likely than arms races alone to produce unwanted conflict.

Every war in history has had its "blundering generation," as one historian called the American generation of the 1850s that set the stage for the Civil War. Churchill, reviewing the origins of World War I, concluded that "far more than their vices, the virtues of nations, ill-directed or misdirected by their rulers, became the causes of their own undoing and of general catastrophe."

The long innings of the weapons technocrats have not enhanced nuclear stability and probably cannot do so without the political "infrastructure" Jackson wants to build. If political communication and comity break down entirely, no mechanical balance of weapons will suffice to put the world at ease.