Martin Luther has daddy issues: The 16th-century theologian (as portrayed by basset-eyed Joseph Fiennes in this passionately square biopic) is searching for a deity that loves him unconditionally -- unlike his pragmatic earthly father, who reacts to his firebrand son's ''heretical'' attacks on clerical corruption by counseling him to ''try and keep your big mouth shut.'' Anachronistic idioms aside, I wish Luther had made a bit more use of its father figures, fleshly and divine. They're the film's only avenues of personal insight into the man who sparked the Protestant Reformation.
The rest of the action is all heady theological badminton, as vigorously thoughtful as it is piously historical. Fiennes delivers polemics against relics and indulgences with the flair of a stand-up comedian: ''Eighteen out of 12 apostles are buried in Spain,'' his Luther muses to a laughing crowd. But the man himself all but vanishes in a Bosch-like tangle of minor characters and textbookish details. Rising above the throng is the great wreck of Sir Peter Ustinov, who, as the canny, saucy German Prince Frederick, distinguishes both himself and the movie.