One of the answers is being a dad to his two boys, James, 8, and Henry, 2. Becoming a father is a classic catalyst for getting one's shit together—but in Farrell's case it was a slow-acting cure. "When I had James, I made a decision not to change," he says. "I literally said, 'I'm not changing! I'm gonna be his friend!' Like a fucking 28-year-old drug-addicted drunk friend is exactly what my 6-week-old son needs." After two years of substance-fueled fatherhood, he thought, "Why am I resisting?"

"That was a whole by-product of fame," Farrell says. Not changing was his way of staying true to his Dublin roots, of keeping alive his outsider status and his sense of himself as removed from the drive and ambition it takes to fuel sudden fame.

"There's a form of expat guilt," he says. "I feared people at home would think I'd changed. So my Irish accent got stronger in America. This was me coming in and going, 'I don't give a fuck!' But, of course, not caring is a form of caring."

His public image was the product of a great deal of effort to make his ascent look effortless. "I wore the same fucking pair of boots for 10 years," he recalls, laughing. "From Cape Town to Tibet to L.A. to Dublin without laces. The same fucking grubber boots that I bought for fucking 20 pounds in a market in London. Initially I wore them because I didn't want to care about how I looked, and then they became my identity. They became my character. And then I wouldn't wear anything else—the idea of it put the fear of God in me."

In 2000, Farrell met the director Joel Schumacher in London to read for a part in the Vietnam-era army drama Tigerland. "We read 44 actors in three days," Schumacher recalls. Farrell, who was doing some TV in Ireland, was an hour late for the audition.

"He had a T-shirt on, a motorcycle jacket, I'm not sure if he'd had a couple beverages by this point," Schumacher says. "He walked in the room and it was the same feeling I had when Julia Roberts came to my house when she was 20. It's almost a little like falling in love—I can't explain it."

Schumacher told him to watch Hud and Cool Hand Luke, and he cast him as the lead in Tigerland and again in Phone Booth (2002), his breakout role. Within a year, Farrell was working with Steven Spielberg on Minority Report, and a year after that he was in Oliver Stone's Alexander, reportedly making $10 million.

One way to keep the folks at home from thinking he'd gone Hollywood was to put them on a plane and import them for premieres and parties—so that they'd go Hollywood too: "I'd fly over loads of uncles and aunties. I think the most I brought over at one time was 30 friends and family. 'Cause the money back then was fuckin' stupid, man! It was so stupid."

In truth, the money isn't so bad now either. What's really changed is his relationship with status and the strangeness of his chosen profession. Get him talking about the good/bad old days and you quickly realize that celebrity itself was one of the mind-altering substances he indulged in, grappled with, and is finally beating, one day at a time. My name is Colin, and I'm a movie star . . . [Forgiving applause]

"It's very easy as someone who has in his life a certain amount of material wealth, but the best thing about fame is debunking it," he says. "The best thing is that you get to go, 'Oh shit—I've just knocked a big one off my list and it does not lead to happiness.'"

• • •

"Aww, it's funny, man—these fucking interviews . . . "

Farrell arches those famously emotive eyebrows—they could be twin shaggy characters in a Dr. Seuss book or a pair of Afghan hounds up on hind legs—and the look says: Are we really going to keep talking about the old exploits?

We've cooled off in the pool and rehydrated and are now returning to the sauna. I've sweated out more toxins in an hour than Farrell's seen in seven years, but here we are still talking about his past.