The world hasn't suddenly gone crazy. I' only seems that way.

Despite the terrorism that swooped down on the nation's capital this week, there was nothing new in the "madness," and only a little in the methods. Hostage-takoing has an ancient history. What made it seem so suddenly, shockingly different was the pervasive awareness of what was happening while it was happening.

Like the war in Vietnam, it came home, instantaneously brought to the living room by television's on-the-spot coverage, punctuated at the doorsteps by the morning and afternoon headlines, freshened by radio broadcasts in between.

As a federally funded task force on, disorders and terrorism reported in a comprehensive volume just last week, terrorism "impinges on the human consciousness with ever-increasing force, thanks to the miracle of modern mass communications."

The task force director, H.H.A. Cooper, puts it even more succinctly. "To adapt a famous Churchillian epigram," he said, "'Never have so few succeeded in causing so much concern to so many.'"

Common crime and human carelessness take heavier tolls of life and property, even on a worldwide basis. For instance, Cooper points out, during the emergency produced by the Mau Mau terrorism, more Europeans were reportedly killed in traffic accidents within the city limits of Nairobi alone than were murdered by terrorists in all of Kenya.

In the United States, cooper added in a telephone interview, terrorism in all its manifestations is still "a very, very minor part of the crime pricture."

According to FBI crime statisticians, for example, there is one murder every 26 minutes somewhere in the United States. No one even attempts to keep track of how many of those homicides are the result of hostage-takings or other terroristic incidents, but the proportion, experts agree, is minuscule.

In a way, the seizure of more than 130 hostages by Hanafi Muslim gunmen here, or something like it, may have been inevitable after the rash of frightening but less ambitious seizures by frustrated loners in Indianapolis, Silver Spring, Wheaton, Warrensville Heights, Ohio, and elsewhere. Terroristic activity, the task force's 661-page study observed, tends to be contagious. And the probability of escalation is especially high if the first effort to make a stir is relatively modest.

"Often, after the use of novel and seemingly successful terroristic techniques has been widely publicized, they have been imitated and embellished by other terrorists," the task force, which was headed by former D. C. Police Chief Jerry Wilson, reported. "Much quasi-terriristic activity may be explained in this way."

Thus, there was a burst of major bomblings - a dozen within a week - in the fall of 1975. And before the kidnaping of Patricia Hearst on Feb. 4, 1974, an FBI official recalls, there hadn't been a significant number of sensational kidnapings for years, but then suddenly there was a spate of them, such as that of Atlanta Constitution editor Reg. Murphy. Skyjacker D.C. Cooper had a host of imitators after he took over a plane in 1971, collected a ransom and parachuted to earth. Neophyte hijackers started demanding parachutes as a matter of course. Cooper's exploit, the task force pointed out, even led to "structural modificiations in that type of plane to prevent the same technique from being used again."

Mass violence and what task force director Cooper calls "political manifestations of terrorism, the bombing of the U.S. Capitol and that sort of thing" has abated considerably in the United States since the crescendo of antiwar protests in the early Nixon years. Similary, attacks on law enforcement officers reached a peak in 1970, according to the task force report, when 25 were killed or wounded in ambush, then tapered off steadily, down to zero in 1975. Campus disorders hit their high in 1969 with 49; there were non in 1974 or 1975.

Hijackings of U.S. aircraft also hit their peak in 1969 with 40 attempts, 33 of them successful. They dropped sharply in 1973 with the advent of metal detectors and the anti-hijacking treaty with Cuba. According to the FBI, there were only seven such incidents in fiscal 1976.

But while all this has subsided, Cooper feels "the type of private terrorism" that has been occurring lately "is definitely on the increase" in this country.

It's difficult to say how much because records are not kept," he said, "but there's been a tremendous volume of quasi-terrorist behavior" - such as the taking of hostages. (True terrorism, he points out, is really characterized by a prospect os securing a transfer of political power of seizing power by terroristic means.)

A member of the task force, Dade County Circuit Court Judge Seymour Gelber of Miami, said he noticed a "numbing sense of shock" over the Hanafi Muslim incident there, too, again thanks at least in part to instantaneous communications.

"A lot of things that happen in Washington are happening only in Washington," Gelber added. "But this, I think, happened all over. You become a part of it, watching the camera going from one building to another, and then zeroing in on Carter."

A judge in the juvenile-family division of the court system, Gelber said he thinks that the current spate of violence reflects a basic change in society over the past few decades. "It's a new mindset," he says. "I've been working on school violence and I find relationships with authority have changed tremendously. I think we've become more accepting of violence."

But he said he tended to agree that madness, if that's what it is, probably set in some time ago and that we may only how be realizing it.

"In recent times, just the techniques have changed," he said. "We don't have the riots we did, but we have individual acts of violence. It used to be planes that were hijacked. Now it's taking over a building."

In short, said Cooper, the spurts are essentially faddish. "In a way," he said, "terrorism may be something whose time has come - like the hula hoop."