ABC Entertainment president Fred Silverman restrained himself when I reached him by phone in Hollywood to ask his recreation to an ABC pilot called "SOAP." He said, matter of factly: "It's boffo."

That, in show business terms, means that Silverman is more than pleased with the progress of a project that could have the same impact on television programming that "All In The Family" had eight years ago and that "Mary Hartman, Mary Hartman" had more recently.

"SOAP" is not a takeoff on the afternoon Soap operas. Susan Harris, who wrote it, and Paul Yunger Witt, who with Tony Thomas is producing it, told me on a recent visit to Hollywood that it was a comedy melodrama.

Harris said it owes nothing to "Mary Hartman, Mary Hartman," which she has seen only a couple of times. She thinks "MH.MH" is satire. Some would disagree with Harris on that point. I sometimes have the feeling when I am watching "MH, MH" that it is not so much a satire about American life as a documentary.

I have not seen the pilot of "SOAP," but I have read the script and its accompanying "bible" - the outline Harris has provided for the development of 42 characters over a period of five to seven years.

Unlike "MH, MH," SOAP is about two upper-middle class families in Connecticut, the Tates and the Campbells. The families are related through Mary Campbell and Jessica Tate, who are sisters.

Jessica is married to Chester, a stockbroker who watches skirts as avidly as he does the Dow Jones Industrial Average. She is having an affair with the young tennis pro at the country club. So is her daughter, Corrine, a girl who is either a nymphomaniac or very anxious to please.

There is also a son, Billy, who seems normal, and another daughter, Eunice, who never smiles.

Rounding out the Tate household is Benson, a black cook-housekeeper who hates all whites except Billy and major, Jessica's father. He served with Patton in World War II and has suffered from amnesia ever since. He still wears his uniform because he thinks the war has never ended.

The Campbell household is just but loony. Mary Campbell, when she was young, wnated to marry Chester, but wound up marrying Johnny Dallas, a member of the Mafia who ran Rockland County for the D'Annuzio family. They had two children, Danny, who is normal except that he doesn't think his brother, Jodie, is gay - a fact that was escaped no one else.

Now, the plot sickens. There are two big secrets in the Campbell household. One is that Danny is really the issue of Mary and Chester Tate. The other is that Danny's stepfather, Burt Campbell, who is in the construction business, killed Danny's supposed father, Johnny Dallas.

I mention all this not in any conscious effort to confuse you. What has fascinated me about this pilot since I first heard about it last year is the possibility that a series like "SOAP" can not only get on the air, but that if offers so many scheduling possibilities.

Harris and Witt think there is enough material to sustain the show for two time slots a week. Silverman said he has not yet made up his mind where it will go. He said it could run twice a week, or once a week as an hour show in prime time.

He even held out the possibility that ABC might run it at 11:30 p.m., right up against Johnny Carson on NBC. It is that kind of a show, and it tells a great deal about how far television has come since Norman Lear persuaded CBS to give "All In The Family' a chance.

A great many of us like to talk about the Golden Age of television (the 1950s). The fact is the television comedy has come a long way in the past eight years. Norman Lear was able to break open the door television executives wanted to keep closed on comedy that appealed to anyone past puberty.

Y"SOAP" probably will open that door wider, and not because it is salacious or suggestive. It will be successful because it is outrageous. It is so far-fetched that people will accept it as pure make-believe. You can do almost anything in television - and get away with it - if people don't think it applies to them.