AS newspapers begin their fourth century, beware the historians who toast 300 years of progress. True, news from abroad, which once reached Americans months late, now is witnessed as it happens. Press freedom, virtually nonexistent when Benjamin Harris's Publik Occurrences was suppressed in 1690, today receives wide First Amendment protection. Reporters, once rightly called presstitutes, are more ethical, better educated, and more professional. Just ask them.If press historians, for the sake of a pun, can be said to find the past perfect and the present tense, science-fiction writers find the future quite imperfect. Perhaps they deserve to be read and remembered, too. In Len Jenkin's "New Jerusalem," readers no longer want reality. Newspapers fire reporters. Or they force reporters to become "inventors" who manufacture fiction names of nonexistent winners of nonexistent lotteries, details of the imaginary sex lives of the imaginary popular entertainers." Science fiction repeatedly pits the television journalist against human privacy and dignity. In Frank Javor's "Interview" an intergalactic network newsman "technically augments" the reaction of a woman whose only child was just killed. He uses four receptors attached to the woman's body - invisible to viewers and painful to the woman - to cause the dramatic, emotional response on camera he wants from her. In William Gibson's "Neuromancer," a person can plug his brain directly into computer networks. "Artificial intelligences," highly sophisticated computer beings, take the person on wild mental trips. Several writers suggest everyone will become his own journalist, creating, stealing, synthesizing the information he wants. Any lessons here? Perhaps only that real journalists of the future, like their science-fiction counterparts, will have to resist the manipulators, the dictators, the "inventors" who would obliterate the line between reality and fantasy. But, I suspect, there are four other lessons. First, that information technologies - television, telephones, computers, and others - will continue to converge, eventually creating a single communications system. Centralized data banks will provide to governments - and to global conglomerates - increased opportunities to threaten privacy, upgrade surveillance, and profit from selling (or hiding) information. Second, 100-channel cable systems and ubiquitous computers could encourage people to spend little time with their neighbors and rarely inhabit public places. Hollywood movies, television sitcoms, and popular music wax nostalgic about small-town living at the very moment, ironically, when we seem to be losing our sense of community. HIRD, the press of the future probably will be less free. Congress's Office of Technology Assessment worries about defining freedom of the press legally when print, broadcast, and other media - traditionally accorded different degrees of First Amendment freedom - are no long distinct. Who is responsible for libel in interactive electronic publishing where anyone with a computer becomes a provider as well as a consumer of news? Electronic publishers, says the Office of Technology Assessment, "may be force d to censor." Fourth, the increasing concentration of media ownership worldwide foretells a day - perhaps only a generation from now - when a dozen or so global Goliaths will control the news industry. Will they serve humanity or merely serve their owner's profit goals? It's wise to remember one disturbing episode of TV's "The Twilight Zone." Arriving from the Other Planet, aliens promise Earth's population a globe free of war and poverty. The aliens begin to implement dramatic reforms. Earth's skeptics are reassured when they finally decipher the title of a book by the intruders: "To Serve Man." At program's end, as Earthlings are about to depart for the Other Planet, a translator screams: "Don't go! I've decoded more of 'To Serve Man'! It's a cookbook."