But the more we see of Renton, the more obvious it becomes that McGregor has plenty in common with his American idols, and less with, say, the later generation of actors -- Brando, Dean, De Niro -- who might be more easily connected with Renton's streetwise demeanor, his seemingly completely modern edginess. As Renton -- and in almost any of the roles he's played since then, from Iggy Pop-style rock star Curt Wild in "Velvet Goldmine" to the simple-minded bird-keeper, Billy, in "Little Voice" to the hapless kidnapper Robert in "A Life Less Ordinary" -- McGregor shows an astonishing subtlety, an almost disconcerting inner gravity, that owes more to old Hollywood than to its more recent past. In "Trainspotting" in particular, he is, quite simply, a joy to watch -- in the way consternation crosses his face as gently as a cloud drifting across the landscape, or the way his features soften and open up, like time-lapse photography of flowers unfolding, when he takes a hit. You see some fragility in the way McGregor carries his round-shouldered, lanky frame (he dieted down to 140 pounds for the role), but the resolute bounce in his gait also betrays an almost shockingly buoyant confidence. There's a visceral quality to his charm that's both timeless and completely modern: He conjures average-guy sweetness without shambling. He transmits a crackling erotic charge, though he's too much of a goofball to really smolder. The intelligence in his eyes is always readable, and his comic timing shows the agility of an acrobat.

But all that said, McGregor is also maddeningly elusive. I've adored every single one of the performances I've seen, and I've watched him closely, but I find myself dumbstruck in trying to get a handle on him. For that reason alone, it makes sense that McGregor should play the sapling Obi-Wan Kenobi in George Lucas' "Star Wars" prequel, "The Phantom Menace." McGregor and Alec Guinness (who played Obi-Wan Kenobi in the original "Star Wars") are completely disparate actors -- Guinness has always traded heavily on understatement, and always makes a graceful bow to formality; McGregor, far more casual, just seems to wing it, with stellar results. There's a prevailing notion that McGregor generally plays high-strung, vaguely scruffy vulnerable guys, but even the performances that fit that description in the most basic way are all radically different. Guinness is the kind of actor whose looks are hard to pin down -- it always seems as if he could be anyone. McGregor has star quality in spades, but he's always able to slip that quietly into a role, to flesh out all its dimensions without shouting, stretching or wriggling.

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