THE INTERNAL SECURITY issue lay comatose in Washington after Congress unplugged its previous life-support sytems -- the House Committee on Un-American Activities and the old Senate subcommittee on internal security -- during the mid-1970s. Now the issue has been resurrected and has gained a new fulcrum in the security and terrorism subcommittee, created by Strom Thurmond after the Republicans won control of the Senate last November and Mr. Thurmond became chairman of the Judiciary Committee. Chaired by Sen. Jeremiah Deaton (R-Ala.), the subcommittee has stirred deep anxieties among civil libertarians about a possible return to McCarthyism.

Nto only internal security but the word "McCarthyism" itself became denatured during the 1970s. Even the friends of Spiro Agnew and Richard Nixon found it a convenient charge to level against overly inquisitive -- or slanderous -- congressmen and reporters, and only weeks ago the Rev. Jerry Falwell attacked the American Civil Liberties Union for allegedly using "old McCarthy scare tactics" in criticizing the Moral Majority. "McCarthyism," in short, has become a politically contentless notion.

During the early 1950s, when Joseph McCarthy was in power and in fashion, the "ism" meant something more precise and ominous. For a half-decade, the frenzied pursuit of communists in government and of ideological heresy in general polarized political life in Washington. Sen. McCarthy and his companions manipulated the internal security issue for headlines, exaggerated the actual dangers of communist infiltration in America and destroyed the chances for normal political relationships within the government, first under President Truman and then into the Eisenhower presidency, until the Senate finally condemned Mr. McCarthy in 1954. Behind the shield of congressional immunity, he had sought to persuade the public of the shameful untruth that anti-communist Truman liberals and Norman Thomas socialists drank from the same poisoned doctrinal well as the American disiciples of Joseph Stalin and that all of these should be deprived of ordinary political amenities and right. these should be deprived of ordinary political amenities and rights.

Today that time of ravaged careers and reputations, the "McCarthy era," finds some defenders, but not very many. If anything, the historical distortions of the period fashionable today misconstrue and misread McCarthyism's malicious impact much as Sen. McCarthy himself wildly overstated the notion of communism's pervasiveness in the United States. This latter-day misconstruction holds that there was no such thing as Soviet espionage -- rather than that the charge was hurled at people who weren't Soviet agents as well as at those who demonstrably were. And it also involves believing, falsely, that there were no far left or even Stalinist folk within the political culture -- rather than that the American political system must protect the rights of such people to hold and propagate offensive views. Nor do young people and propagate offensive views. Nor do young people in the 1980s learn enough about the struggles fought by the resisters to defend civil liberties in that earlier time of widespread fear.

For those in the center, both McCarthy's view of reality and today's dubious correctives pose major problems; the one exaggerated the internal security problem while the other denies it entirely. Throughout this century, the internal security pendulum has swung from periods of overreaction such as Sen. McCarthy's worst years to times when the country disregarded the issue, as if inattention alone would dispose of the problem.

Those now reviving the internal security issue in Washington should study carefully its turbulent past. Years ago, the poet Marianne Moore described her craft as one that involved the portrayal of imaginary gardens with real toads in them. Unfortunately, all too often in this century, those in government who have raised the issue of "subversion" have cultivated "imaginary gardens," while the more difficult job of tracking the "real toads" -- foreign agents and their American accomplices -- has been left to professional counter-intelligence specialists.

Rarely have legislative probes been effective in uncovering / spies and traitors, whether of the right or the left. At the same time, the threat posed today to American society both by foreign agents -- pursuing, more often than not, high-technology secrets in lasers, microelectronics and new weapons systems -- and by internationally connected terrorist groups remains genuine and serious. Whether or not the new subcommittee on security and terrorism can play a serious role in helping to meet this threat is a subject to which we will return.

For the moment, it remains only to caution the subcommittee against taking any steps that might fulfill either the wild hopes of its sponsors in the "old boy" internal security network or the comparably extravagant fears of its detractors. Both groups, each for its own reasons, await some rowdy "last hurrah" of Red-baiting. Both sides gird to restage their ideological fantasies of the McCarthy era. Political common sense alone should encourage the subcommittee to disappoint these expectations, to focus instead on the "real toads" of espionage and terrorism, and to avoid -- at all costs -- another destructive trek through McCarthyism's "imaginary gardens."