EVERY FRIDAY AFTERNOON in Moscow, Idaho, a strange commotion overruns Main Street. A stream of young men and women parade down the sidewalk, wearing black academic gowns that billow and flap as they walk. Some pore over Latin textbooks or thumb flashcards of ancient Greek vocabulary, nearly tripping at the curb. They are students at New St. Andrews College on their way to disputatio, a weekly assembly held in a movie theater downtown. The college itself has no room large enough to accommodate all 150 students at once: it occupies a single unassuming brick building a few blocks away, one that a stranger might mistake for the refurbished husk of an old savings and loan. Passers-by on their way to the Pita Pit or Hodgins Drug barely give the students a second glance. Not a few residents, however, have fought hard to keep them out of downtown. Founded in 1994 by the elders of a fast-growing and radically...