In the runup to the Academy Awards this year, Ron Howard’s film, A Beautiful Mind, caught a remarkable fusillade of criticism from various Cassandras ranging from Matt Drudge to Andrew Sullivan. With the film now released on DVD and video, it’s worth reviewing the controversy.

The movie, a “biopic” adapted from the Sylvia Nasar biography of Nobel Prize-winning mathematician John Nash (Simon & Schuster, 1998), “left out” important things, the critics said. It did not describe a homosexual affair Nash had apparently had as a young man. Late in the mud-slinging, Drudge dredged up accusations (against the real Nash) of anti-Semitism. One wonders if the critics actually read the book. The movie leaves out a whole lot else.

More important, screenwriting is all about what you leave out.

Nash had a number of what might be called “gay affairs,” but that would be stretching it. They were, more accurately, desperate neurotic lurches driven by terminal geekiness, a near-autistic inability to relate to other people. It is unclear whether Nash ever consummated any of these fumbles. One such included an unbidden crawl into a 15-year-old boy’s bunk — what would today be called an assault. And in 1954, Nash pulled a George Michael in a Santa Monica beach restroom and got busted. The local cops turned him over to their pals in the security department of the RAND Corporation, where Nash was doing top secret work. RAND fired him, and told him to get out of Dodge.

Before that, in Boston in 1952, Nash had begun an affair with a woman, Eleanor Stier, who was older than he. By the following year, Eleanor was pregnant, and gave birth to a son, John David Stier. Nash, a snob about social status, looked down on the working-class Eleanor and never gave the slightest hint he might marry her. Indeed, he abused her and his son by neglect for years. Nash’s cruelty in these two relationships is almost beyond description. Nash married Alicia, the wife pictured in the film, some years later, and had another son, also named John — as though the first son did not even exist.

One way or another, the critics raised most of those “omissions.” But for a screenwriter, that’s just part of the unwieldy territory. There’s more.

John Nash worked in a milieu — higher mathematics — beyond the understanding of, literally, 99 percent of the population. For most people, mathematics means arithmetic. I got a 650 on the math SAT in 1965, when the scores really meant something, and I could not follow a single mathematical proof or example in the book, A Beautiful Mind. That was the daily stuff of life for Nash. How do you represent his work?

And how do you represent his professional life? Nash worked in a loosely knit, but devoted, community of perhaps 200 mathematicians and academicians, the best in the world, many of them with incomprehensible (to a movie audience) foreign names — all of them working on ideas that set them completely apart from the rest of the world.

When Nash went nuts — he succumbed to schizophrenia in his twenties, which ruined him for decades — he fell into bizarre fantasizing that included anti-Semitic world conspiracies, crackpot numerology, and a determined attempt to renounce his identity, even his citizenship, as an American. He abandoned his wife and son (the legitimate wife and son, that is; the illegitimate pair he had long ago renounced) and bounced around the world for years. Alicia divorced him, though they did stay together, after a fashion. For a screenwriter, the geography alone is crazy-making.

So: You’re a screenwriter, you look at this material, and you know certain things. You know that if you’re going to work with a hot movie star (Russell Crowe), if you’re going to have that movie star play a hero, there are certain things you cannot do. You cannot make him an abuser of woman and children, an anti-Semite, or a weenie-wagger. You cannot present the abstractions of mathematics, not really, to a general audience. You cannot let your story get hijacked by politically loaded revisionist emotionalisms, like the gay agenda. You absolutely cannot show the worst of schizophrenia, which is not romantic, but heartbreaking, even disgusting. Childhood? Back story? Forget about it — no time.

Here’s how you focus: You’ve got one of the great mathematical geniuses ever, who at a young age develops a theory at first poorly understood, but which later becomes pivotally important in economics. He goes crazy, so crazy he loses everything. But his friends and his wife stick by him because, as one of those friends says, “He was worth doing the very best for.” His colleagues eventually let him hang around Princeton, being crazy, being “The Phantom,” as he was known in those years. And eventually, through something like grace, Nash comes out of it. (Few schizophrenics do.) He gets a handle on delusional thought, and puts himself back together. And right about that time, the world as a whole recognizes him with the grandest prize of all, the Nobel.

That’s the story: Redemption through grace. Anything that gets in the way of that, you leave out. You leave out the illegitimate son and neglected mistress, you pare down the cast to a half-dozen important colleagues, you forget about any locations except Princeton and MIT. Scratch the divorce. You make up a hallucinatory filmic language to convey both Nash’s genius and his insanity, even going so far as to create three wholly imaginary characters to people Nash’s delusions. You stick with the friendship, the support, the love, and the ultimate triumph.

You keep the true emotion, and you keep the emotion true. You don’t hurt the book; the book is still there, for anyone who wants to read it. You don’t do anything cheap. And if you are a wonderful filmmaker like Ron Howard, you make the best biopic since Pride of the Yankees.