"I believe in the infinite potential of the human spirit," says Alan Thicke, as a psychiatrist, early in the premiere of the ABC sitcom "Growing Pains." For a show like this to brandish the infinite potential of the human spirit is like Larry Flynt waiting at home for the Nobel Prize committee to call.

Here we have reached the nadir, the bottom, the subterranean depths that lie beneath the dregs: "Growing Pains," at 8:30 on Channel 7, is state-of-the-art bad, and definitive tastelessness as well. When a snide teen-age son spots Mom and Pop kissing in the kitchen, he snarls, "What's the matter, you guys aren't getting enough?" He also says, "Come on, you can't hit me, Dad; you're a liberal humanist."

"Growing Pains" isn't just an argument for corporal punishment. It's an argument for capital punishment.

Though married 15 years, the parents behave like panting adolescents at a drive-in movie. Dad keeps pawing Mom, and seems to regard the children as irritating obstacles to marital sex. One can only imagine what kinds of perversities this Frankenstein is creating on his psychiatrist's couch. The premise of the show has the wife (Joanna Kerns) returning to the work force after a long absence and the husband dealing with the adjustments, but nothing on the program has much to do with that situation or with the attitudes and behavior of functioning human beings anywhere.

The children are braying brats and the parents cowering twits. Households like this make the Manson family look good. Thicke, who bombed in a syndicated talk show last year, is called multi-talented in his press releases, but the word that comes to mind after his simpering performance here is anti-talented, and that's being generous.

Writer Neal Marlens, who will be atoning for this one for the rest of his life, springs his final nifty at fade-out time: Pop the prankish shrink pulls down his pants to "moon" his son, but the wife walks in instead. "Growing Pains" leaves behind it the entertainment equivalent of soap scum. 'The Other Lover'

A sweet nothing generously sprinkled with scenic San Francisco, "The Other Lover," a CBS movie at 9 tonight on Channel 9, brings as much intelligence and class to the romantic melodrama genre as probably can be brought at this point in time -- and perhaps as much as it can bear, too. No, it isn't "Brief Encounter," but it's brief, and pleasant to encounter, and though the two leads can't exactly act, they pose against each other nicely.

Lindsay Wagner is a married publishing executive and Jack Scalia, the one-time model, is a maverick young novelist (he puts on little round glasses to try to look like a writer), and one day her supple Jaguar bumps into his cute little red Fiat and it's love at first rear-ending. Of course prime-time morality does not countenance adultery, and just as well, and networks don't like TV-movies with unhappy endings, so the tension in the script devolves from wondering not what will happen to the lovers but if the writers will finesse their way out of this situation by the time Gordon Peterson and the Eyewitness News Team are looming on the horizon.

"Equality in the bedroom is like equality in politics; it kills the instinct to participate," quoth the author (hey, this guy's a real intellectual, ain't he?), but that's before the smooching starts. Writers Judith Parker and Susan Title bring the pair together, but it is director Robert Ellis Miller who launches them into deep smooch. One kissing sequence is a rather subtly erotic lips de deux, shot in daring close-up. Our lovers kiss on the dance floor, they kiss by a pillar, they kiss in the car, and of course, they kees kees kees in le boudoir!

Miller, who flatters the material without inflating it, once manages to get the two performers' bare chests pressed together during an embrace -- ooh, la la! He also sustains a long conversation during a cable-car ride, much of it in a single take. A climactic confrontation regarding love and loyalty was edited into a lilting montage of dewy dissolves. Yes, it does look a little like a perfume commercial, but some of those perfume commercials are darn sexy.

"Last night was wonderful," says the writer after the first blissed tryst. "No -- it was more than wonderful." Herewith a prediction: Whatever else happens between now and then, in the year 2085, maybe even in the year 3085, movies like "The Other Lover" will still be made, and there will still be enough of us mushy old pushover types around to lap them up.