Washington ? The restatement of the United States’ fundamental defense doctrine issued by the Bush administration last week substituting pre-emption of potential threats for containment of aggression is probably the most dramatic and far-reaching change in national security policy in a half-century.

But it is also part of a pattern of radical revisionism in basic governmental philosophy and structure engineered by George W. Bush, who is quietly rewriting the classic definition of conservatism.

The word, as this president uses it, has little or nothing to do with the traditional conservative inclination to preserve the status quo. Instead, it suggests a very bold and risk-taking readiness to re-examine, revise and restate basic tenets of government. It is a pattern that now pervades Bush’s economic, social and foreign policy and makes this, in some respects, a truly radical government.

Consider economics. The centerpiece of Bush’s policy is his belief in the efficacy of tax cuts under any and all circumstances. It was hardly novel for a Republican president to push for lower tax rates early in his term, as Bush did last year. And the budget surpluses then accumulating caused opposition Democrats to agree that revenue reductions, slightly smaller in scope, were appropriate.

What is different is Bush’s insistence that tax cutting should continue, even with the return of budget deficits and even with the prospect of staggering, long-term additional spending on the military, homeland defense and the war on terrorism. Facing deficits in his second year, Ronald Reagan acquiesced in Congress’ rollback of some 1981 tax cuts. In a similar situation in his second year, the president’s father made the same concession to a Democratic Congress. This George Bush has broken the pattern.

Consider education. The hallmark of conservative thinking has been the insistence on local control of schools. Bush has pushed through the largest expansion of the federal role in education of any president since Lyndon Johnson, not just in dollars but, more importantly, in standards of performance and measures of achievement, backed by real sanctions.

Consider social programs. Bush has backed an ongoing effort to shift the line on church-state relations, bringing civil and religious authority much closer together. He proposed direct public funding of parochial schools and applauded when the Supreme Court approved the Cleveland voucher plan. He has lobbied hard for legislation that would route much more federal money aimed at meeting the needs of troubled individuals and families through churches, synagogues and mosques. For good or ill, he is trying to narrow a gap that has existed between the clergy and the government since the start of this republic.

Consider retirement security. In the face of cautions from members of his own party and strong criticism from the Democrats, Bush has kept on his agenda the proposal to change the Social Security program that staple of New Deal policy to permit individual workers far more freedom to devise their own basic pension plans, with all the potential risks and rewards such a change might entail. If Republicans regain control of Congress in this election, he almost certainly will try to make this concept law.

And now Bush has put before the world, first in his West Point speech and last week in a formal state paper, a fundamental revision of American foreign and national security policy.

That policy developed in stages, from the imperialism that marked the decades before World War I, to the isolationism that prevailed between the wars, to the bipartisan “containment” policy that evolved during the Cold War. The common characteristic of the whole 20th century was the readiness of the United States to respond to threats to its security and its reluctance to initiate conflict or issue ultimatums to anyone. When aggressors pushed forward, we pushed back hence, Korea, Vietnam and the Gulf War. But we did not start fights ourselves.

Now, with the doctrine of pre-emption justified by the all too real threat of terrorism, Bush is proposing to scrap that distinction. Instead, he asserts the right of the United States, as the only superpower, to judge the degree of potential danger itself and to take whatever action it deems necessary to eliminate that threat.

You may think any one of these changes is wise or foolish. What is remarkable is that all of them have come in so short a time from the hand of a man whose campaign seemed so bland and whose election was so narrow. Bush really is redefining what it means to be a conservative.