I vaguely remember reading about a theory about sexuality that was later discounted.

It was that homosexuals are created by the behavior of their opposite-sex parent. That is, if mommy was mean, a boy would end up gay. If daddy was mean, a girl would become a lesbian.

That sort of thinking has gone the way of the rotary phone, but that old theory would almost seem to be born out in Terrance McNally’s 2013 play, “Mothers and Sons,” currently on stage at City Lights Theater in San Jose.

In it Katharine, the mother of a gay son who had died of complications from AIDS 20 years before, shows up at the Manhattan apartment of her dead son’s lover, Cal. If a mean mother could turn a son gay, Katharine might be such a mother.

Lillian Bogovich is absolutely brilliant as Katharine.

Her face broadcasts her pain and unhappiness. She is crippled by her feelings, although she struggles to maintain what she probably thinks is her serious-minded superiority.

From the audience, it is like watching a person being freshly injured as each emotional hit strikes home. When a thought of her son arises, she is stricken from heart through face.

She criticizes what Cal calls a “remembrance” he organized, 20 years ago for her son and his lover, Andre. It was “a little too gay for me,” she says.

She is bitter to the bone, and angry. She blames Cal, and New York, for her son’s death.

“Andre wasn’t gay when he came to New York!” she exclaims, which got a good laugh from the audience.

Cal eventually defends himself: “I didn’t give him AIDS. I didn’t make him gay.”

“Well, someone did!” she says.

Over the course of this play, we come to understand that Katherine has never been happy. Not as a mother, not as a wife, not even as a child. And she blames everybody else.

Now a widow and a mother who has seen her child die, she wonders if she should end her own life.

But this play is only partly about a bitter woman who has little love in her — Cal is still hurt that she wouldn’t hug him at Andre’s funeral. He was hurting, too, and he was the one who took care of Andre as he was being ravaged by AIDS.

The play is also about how the world has changed since the major AIDS crisis of the 1980s. In those days, Cal had suffered not just the loss of his lover Andre, he had suffered the loss of hundreds, of thousands of gay men. His friends, his community.

Twenty years later, he is happily married to a man 15 years younger than he is, Will. In Andre’s day, gay marriage would have been illegal. Gay relations are now largely accepted — at least on the coasts.

Damian is brought to life by Damian Vega, who is now doing very well in life, hence the Manhattan apartment and the happy marriage. He does everything he can to be polite to Katharine, but there are limits.

Max Tachis, whose excellent career largely began at City Lights, is on hand as Will, husband to Cal. Tachis is always fun to watch, and brings a lot of curves and hills and valleys to his dialogue. Some of which is quite funny, because he is not as worried about being polite, as is Cal.

“We didn’t deserve the dignity of marriage?” he asks during verbal sparring with Katharine. “Maybe that’s why AIDS happened.”

It’s clear she doesn’t see the irony.

“Should I alert you when I’m bantering?” he asks her.

Cal had mailed Andre’s diary to Katharine. She was there to give it back. Both of them are cut and bleeding by memories of Andre, so neither is willing to read it.

Will has no such compunction. He is a novelist. (Did you know this? Novelists always peer under rocks and ask the embarrassing questions.) So he reads some of it, which is modestly revelatory.

The verbal dispute continues among the three, and it is a fine performance, well directed by Jeffrey Bracco. It all has to snap and pop for it to work, and it does, a masterpiece of timing.

“Why did your life get better after Andre’s death, and mine got worse?” cries the woman who will not take charge of her own life.

Eventually the two men probably want to eject Katharine out the window to let her fall in Central Park, but by that time Bud, the young son of Cal and Will, becomes a factor. He’s a sweet kid who wants her to be his grandmother. He gets through to her.

That turn in the plot doesn’t really work — McNally’s bad — but young actor Izaiah Gutierrez certainly tries to make it viable anyway.

There are still thousands of people who have AIDS, so in a sense the “crisis” has not exactly abated. The differences include that the medicine has evolved for the better, and AIDS is no long an automatic death sentence.

And better yet, gay people are finding acceptance in more and more places.

We’re all humans, after all. Gay love doesn’t have to hide in shadowy corners anymore.

The elegant set, by Ron Gasparinetti, furnished by properties designer Miranda Whipple and lit by Mary Baronitis, is great. It’s like visiting Central Park West.