McCartney has never solved the problem of eternal youth. Most rock-and-rollers look like simps or cynics by the time they hit 35. Others retain the irrepressible exuberance of a Stevie Wonder, or grasp it again in magic moments the way Carl Perkins does on this album's most affecting cut. A few rare ones age gracefully into fresh-eyed wisdom, like Neil Young and John Lennon. But no matter how serious and sensible he gets, McCartney's perpetual boyishness conveys the perpetual callowness of a musical Troy Donahue. I don't think this is intentional--in his personal life he seems at least as adult as anyone I've named, and he's put his hard-earned craft to mature use on this LP. But it might almost be dumb love songs. B