Sitting under high bookshelves stacked with classics, Hoffman offers his own explanation: “It’s not intellectual. You’re mostly aware of what you don’t like. Henry Moore said something like that. You keep chipping away at what isn’t an elephant. And Miles Davis said: ‘Don’t play what’s there, play what’s not there’ — I’ve put it on my wall. We think the conscious is the determining factor, and actually it’s the least reliable instrument. The knowing is the infringement. You find what is exposed.”

Hoffman is genuinely likable. His candor, his ability to expose himself even in a conversation with a journalist, seems authentic. But as with all great actors, there remains the feeling that everything, even his uncompromising dedication to the forbidden territory of the unconscious, is a performance: his longtime friend and “Fockers” series co-star, Barbra Streisand, once said, “You have to be very careful of him. He will say anything.”

It may well be that the truth about him really does lie in something exterior, something in the shell rather than the kernel of the nut. He mentions a quotation from the psychoanalyst Jacques Lacan that refers to “the armor of an alienating identity,” the idea being that if we have too strong a concept of our own identity, we exclude other formations. In the best possible way, he seems to me like a man on the last leg of a marathon journey of escape from himself.

Partly Hoffman is running from the specter of depression: “It’s tactile, a green knot in my stomach,” he says. “I once didn’t work for five years because of it.” But his escape attempt is also a deliberate process of stripping himself to something elemental. “You go back to being a 2-year-old looking at a leaf, the construct of it. You are doing the same thing again. It’s something in the middle that messes you up.”

There have been constant challenges in his life. In his 20s he was burned very badly by cooking oil. He has confessed to being a premature ejaculator. (“As you get older there is nothing better: at my age it takes an hour and a half so I think I’m amazing!” he once told a journalist.) He brushes aside criticism in the British press for a commercial he did for Sky, at the height of the phone hacking scandal. “Sky’s Murdoch?” he says in amazement. “Good thing I didn’t know, or maybe I wouldn’t have done it, what with my well-known liberal views. They got me . . . I put my hands up!”

It’s nearly teatime in Pall Mall. The room begins to fill with a tinkling of cups. Outside, it’s the magic hour. Hoffman shakes his head. “I have never known how something I was doing was going to turn out. With the project, as with the character, it’s always a kind of revelation. I said that to my wife about ‘Luck.’ ”