Both precepts seem plausible, even if one is harsh and one loving, and both are chewily written. The entire play is like that: ideally worded, ingeniously structured, sinewy and swift. It never lets you, or poor Sister James, reach a conclusion as to which, if either, of her superiors is right. By the time Shanley takes the astonishing step of having Aloysius interrogate Donald’s mother — Quincy Tyler Bernstine, scoring big in a short but vividly counterintuitive role — you no longer know what you believe.