The (London) Times is celebrating its bicentennial by re-establishing its reputation as "the thunderer." When Geoffrey Howe, the foreign secretary, recently delivered a long criticism of President Reagan's Strategic Defense Initiative ("Star Wars"), the Times cleared its throat and called Howe's speech "mealymouthed, muddled in conception, negative, Luddite, ill-informed." Didn't like it.

Howe endorsed research into strategic defense, but expressed both doubt that it could produce a feasible system and dismay that it might. Howe favors what Reagan abhors: the policy of deterrence purely through mutual vulnerability. And he is disconcerted by the thought of an SDI success that would require retiring the 1972 treaty banning antiballistic missile systems. In his speech he called the ABM treaty a "keystone in the still shaky arch of security we have constructed with the East."

Howe flatly asserted that deterrence "will continue to work." His reasons for such faith were promptly subjected to withering analysis by Richard Perle, who serves Reagan as an assistant secretary of defense and was here attending a conference Howe should have attended, a conference on realism about Soviet objectives.

Perle noted that Howe's 27-page speech contained not even a phrase about the enlarging pattern of Soviet violations of that 1972 "keystone" and other arms control agreements. Howe conceded the incontestable, that the Soviet buildup has exceeded "the reasonable requirements necessary for the defense of the Soviet Union." But he rushed to say, in extenuation, that it is reasonable for the Soviets to be unreasonable: "Historical experience has inclined them towards over- insurance."

That thought is suspiciously like the crackpot Kremlinology that a wit once called "preemptive empathetic paranoia." That is, a hard history has made Russians neurotically concerned with security, so we should try to think like a neurotic and refrain from any policy that could seem, to a neurotic, provocative.

Howe's "overinsurance" theory is, Perle said, an unpersuasive explanation of the addition of 8,000 Soviet warheads since the arms control process began in 1969, 4,000 since SALT II was signed in 1979. For persons unenthralled by the mirage of arms control, the explanation is that the Soviets have sought and achieved strategic superiority for the intimidation that flows therefrom.

Soviet violations of the ABM treaty have been combined with deployment of 13,000 surface-to-air launchers to defend against U.S. bombers. How does Howe see in that a Soviet commitment to mutual vulnerability?

Those and other defensive measures, combined with unprecedented expansions of Soviet offensive weapons superior in quantity and quality to U.S. weapons, are designed to menace the U.S. retaliatory capacity, which is the U.S. deterrent. There is no reason for Howe's serene belief that Soviet policy is benign acquiescence in mutual vulnerability.

The reasonable explanation of Soviet enthusiasm for the ABM treaty is, Perle said, cause for caution in today's context of the SDI debate. In 1972 the United States began deploying an ABM system superior to the Soviet system. The Soviets agreed to ban deployments while permitting research (which at that time they admitted could not be limited because limits could not be verified). U.S. research slowed, Soviet research raced ahead, Soviet treaty violations became brazen. The Soviets have deployed twice as many phased-array radars (on which an ABM system might be based) as the United States had planned to deploy in 1972.

Today's Soviet aim in Geneva is to induce similar unilateral paralysis in U.S. strategic defense. Ten days after Reagan's March 1983 speech proposing SDI, the Soviets issued a statement deploring the devotion of scientific resources to military projects, and especially defensive systems. The signers of the statement included the scientists running Soviet strategic-defense programs (which are larger than U.S. programs), the architect of the Moscow ABM system, the head of the military laser program and the designer of the most lethal Soviet missiles.

Howe, his ears ringing from the Times' thunder, should appreciate the civility of Perle, who did not ask, as the Times implicitly did: Why does the Iron Lady suddenly have a papier-m.ach,e foreign secretary? The Times darkly suspects that the lady has been beguiled by an idea and smitten by a person.

Prime Minister Margaret Thatcher may be, the Times says, "distancing" Britain from the United States, the better to be an independent "bridge-builder" to the East. That, says the Times, would be "one of the most ill- fated British decisions since the era of appeasement."

Well, she did say "I like Mr. Gorbachev," but she rather more than likes Mr. Reagan. And although the Times has changed a lot since the days when it was a piercing voice of appeasement, dramatic change, especially in a leftward direction, does not seem to be in Thatcher's repertoire.