Which of our senses do we most take for granted? In the film Perfect Sense, a mysterious plague shuts down humanity's senses one by one, each preceded by an extreme emotion: a profound grief leaves victims with no sense of smell, feeding frenzies precede a loss of taste, fits of rage mean deafness will follow. Ewan McGregor, playing a chef, and Eva Green, as an epidemiologist, meet in the midst of all this and fall in love, even as they themselves lose their ability to smell, taste, hear, or — inevitably — see each other. Fortunately, McGregor has not lost his ability to chat, so Vulture checked in with him about eating soap, taking on his first TV role, and "messy" sex.

Did you spend time with any chefs to prep for your part in Perfect Sense?
I worked with an old friend of mine, Guy Cowans. He has a place called Guy's in Glasgow, and he's also a movie-set caterer in Britain. He became the chef advisor for the movie, for all of the sequences in the kitchen. So I worked with him for about a week, observing, about two or three hours a night, and I actually ended up helping out. I spent a few nights doing service, when it got really chaotic. [Laughs.] I used to be a dishwasher and a waiter when I was 14, 15, 16, so I do have some experience with that, but it's fascinating to watch them keep the orders straight — what steak to cook for how long and all of that. It's really quite something to see. So I was taught how to make several dishes that we incorporated into the scenes. Guy orchestrated most of it; we wanted it to be realistic, for our movements to make sense, so it looked like we knew what we were doing.

You reunited with Ewen Bremner — Spud in Trainspotting — and you act for the first time with your uncle, Denis Lawson ...
That was just delicious. I've waited my whole life to act with Denis. He's directed me [Solid Geometry, Little Malcolm & His Struggle Against the Eunuchs], but Denis is the reason I'm an actor. He's my inspiration. He's the only person to speak to about acting. And Ewen, this is our third film together. We're also in Jack the Giant Killer, acting up a storm together. He pushes himself physically, and goes to great lengths, so he's really exciting to watch.

You both push yourselves to great lengths in the food-frenzy scene. What on earth are you guys eating?
That was actually olive oil he was pouring down his throat! He's not swallowing it, but it looks like he is, doesn't it? My jar of "mustard" was actually custard. It's all stuff you could eat. The guys in the fish market, they were eating big lumps of raw fish, because that's difficult to substitute, so the fish stuff was real. Disgusting, huh? I was lucky not to have to do that one. Oh, and the soap — we didn't have to eat soap. That was a bar of white chocolate, with some kind of foam on it that Guy uses in cooking.

Eating soap is not on my to-do list, although it's a sweet scene in the bathtub. It made me think about how much your sense of smell and taste affect things like falling in love, memories ...
It's really brilliant. It's a simple metaphor, that when you fall in love, you lose your senses. We can't eat, we can't sleep, and it just takes us over. And that would have been good enough, but then the way David Mackenzie shot it was so believable and true, and it somehow elevated the idea way above what I expected. It was a very deep, moving experience. People come up to me and tell me they've had entirely different reactions to it. Some people think it's about mourning the different phases of your life. It just taps into something interesting about the human condition, and it's very unique.

What's your favorite smell or taste, the one you would most hate to lose?
For smell? Oil. Oil and leather. Old metal. Like an oily, old car, an old motorcar or motorcycle. The way when you get off and it cools off, it gives off a rich aroma. For taste? Probably something like a boiled egg with toast, or an avocado with lemon and salt.

There have been a lot of apocalyptic and postapocalyptic scenarios on film lately, but they're usually played for thrills. This is much more a love story. And you've got lots of sex scenes with Eva ...
When the world's about to end, the only thing Eva and I can think about is each other, the need for each other, to fall in each other's arms. We've been reluctantly falling in love, and against our better judgment, at the end of the day — literally at the end of the day for them — what we find is true love. And sex is part of that, an important part of that. It's as intrinsic to this story as music is in Moulin Rouge. I don't shy away from being naked. The Pillow Book, that was about a woman's sexuality, and the idea of not being naked in that is ludicrous. If instead of being naked, you're clutching at a bed sheet, that's nonsense. But I don't like to see the generic Hollywood sex scenes with the bodies glistening — sex is not like it is in some Hollywood movies! Sometimes it's messy, sometimes it's guilty, sometimes it's embarrassing, and you've got to tap into that.

You'll probably have lots of room to explore all of that on The Corrections.
Yeah, but I don't think we'll have to go out of our way. [Laughs.] I haven't seen many of the scripts yet, but it feels like it's going to be accurate to the book, and really detailed. Jonathan Franzen's writing it with Noah [Baumbach], and it looks like we'll have the luxury of time to push deeper through the book and explore parts of the story that aren't in it. That'll be a first.

I was surprised you took the role: I thought you turned down being James Bond in Casino Royale because you didn't want to commit long-term to a role?
Ah, but I didn't turn down Bond. When they were casting it, they spoke to me, and I was one of the actors they considered, but they never quite offered it to me. It's an urban myth!