"Kramer vs. Kramer" is a movie about a custody fight. Ted Kramer is an ad man who has no time for his wife and young son. Joanna Kramer can't take it anymore and walks out: she has to "find herself," as the phrase goes. A year or two later she comes back to announce, "I want my son."

What makes it so wrenching is that Ted has meanwhile discovered the bonds of fatherhood. Usually Hollywood locates love in bed. "Kramer" shows where love in the real world spends most of its time: in the kitchen, the living room, the park -- places like that. Love isn't eternal; it's day-to-day. It brings home the bacon and fries it. It wipes noses. It makes the bed. Sometimes it yells.

You know all that. But you'll be surprised, emotionally ambushed, to see it on the wide screen. I myself am a flinty soul, but my own eyes leaped, flowed and finally squirted. It was all I could do not to fill the theater with the exquisite sound of my sobbing and honking.

Both parents appear a little too noble, and the little boy is just a shade too cute. But any excesses in the script are more than made up for by its general subtle power, and by the perfect acting of Dustin Hoffman, Meryl Streep and Justin Henry.

The film indirectly raises a much neglected issue. Ted has not only sentiment but justice on his side. Yet he is up against a profound legal prejudice: that a child is something like the property of the mother. Ted's lawyer warns him at the outset that he will have a hard time keeping his son -- even though Joanna has deserted both of them. She hasn't visited or communicated, and (it goes without saying) has paid no support. A father who behaved as she has behaved, and who proceeded to demand custody, would be laughed out of court, assuming he could find a lawyer to take his case.

This too is straight from real life. Just as there are faces only a mother could love, there are mother only a judge could believe. In custody battles a mother's record usually counts for less than her sex.

There is something to be said for a presumption in favor of one parent, other things being equal. It may not be fair, but it saves fighting. Conventional inequalities, Samuel Johnson observed, carry no invidious personal reflections. and full equality breeds contention and envy: the loser feels stigmatized as the inferior parent.

Still, when one parent runs off, he or she should forfeit any favorable presumption. Besides, any such presumption is most certainly at odds with current notions of sexual equality. Aren't fathers entitled to "equal protection of the law"?

The feminist movement has been uncharacteristically silient on this question. No wonder: the whole movement for equal rights would lose a lot of steam if it were widely realized what it would mean for men to gain equality, too.

As things now stand, women have a whole series of unilateral rights with respect to children. If a woman is pregnant, the decision whether to abort is hers alone. If she wants to have the child destroyed, her husband has no say in it. If she chooses to bear it, he must support it, whether he wants to or not. With the advent of no-fault divorce, she can throw him out of the house with the assurance that the children will remain with her, at his expense. And if she wants to leave for a while, she can do so with the understanding that she has a good chance to reclaim the children in the future.

Assuming the sexes have identical rights, all this cries out to heaven and the Supreme Court for redress. Maybe the Equal Rights Amendment will take care of it. But feminists avoid the subject, if indeed it ever occurs to them.

All of which suggests that the women's movement is far from a movement for full sexual equality. As with most so-called reform movements, it is really a demand for privileges and exemptions. Such demands are of course made in the name of "rights," but of course that's the only way you can get away with calling for privileges nowadays.

The law has traditionally distinguished between men and women. It is simplistic to talk as if this were nothing more than the oppression of one sex by the other. In the movie, this point is deftly caught when Joanna, testifying in court, explains that she has left home because the marriage was oppressive to her.

No doubt many men have felt the same way. Things are tough all over. If only suffering were schematically distributed, we could releive it all by passing laws and amendments. But it isn't, and we can't.