Film actors are fragile, and if that sounds patronizing, well, it's meant to be: I am their patron, and so are you.
In return for celebrity and riches and seemingly unlimited access to sex, our movie stars need only stay beautiful - which is hard - and wide open - which is harder. They have to switch off the defense mechanisms that keep the rest of us from imploding. It's no wonder they sometimes medicate themselves to death.
History is full of twenty-something casualties and near-casualties, because young actors party hard and program themselves to hold nothing back. They cling to the image of James Dean, who didn't O.D. but lived on the edge and acted there, too.
There is a kind of willed madness to American Method acting: Actors want to show what they do has a personal cost.
River Phoenix kept his childhood pain alive in "My Own Private Idaho" and "Running on Empty." He told an interviewer he wished he wasn't as conscious as he was, and off-screen he sought unconsciousness at every turn. He died at 23 from a mix of uppers and downers.
I could be talking about Robert Downey, Jr., or Keifer Sutherland or Lindsay Lohan - gifted performers whose crazy freedom became, and in some cases still is, a kind of prison.
But the subject is Heath Ledger.
Apart from the loss to his family, the saddest thing about Ledger's death at 28 is that he was still unformed. Was he a great actor? I don't know, but he was on his way to greatness - nakedly desperate to measure up to the stardom thrust on him so suddenly.
Ledger could have gotten by on charm, as in his first lead role in "10 Things I Hate About You." But he brooded and pushed himself and grew as an artist, at a cost to his emotional autonomy.
As the son who can never please his father in "Monster's Ball," Ledger was so raw he was difficult to watch. He wasn't classically trained, and he couldn't take refuge in craft or use the Method to harness his emotions. He went to scary places.
One of them was in "Brokeback Mountain," where as a sort of gay Marlboro Man his cowboy lockjaw and uncanny low tones were hypnotic. He made you feel the unbridgeable gap between his mythical persona and emotions he didn't dare unleash.
In life, Ledger had license to act out too much, and it didn't help that he'd just finished playing the Joker in the upcoming Batman movie, "The Dark Knight" - a role in which he courted insanity, a wild, limitless freedom.
What happened next we don't fully know. But Heath Ledger's death reminds us what a dangerous art this can be.