The Merchant of Venice stays relevant because our modern sensibilities inform how we tangle with its complex characters. Without subtext, we cannot rationalize the central relationships. Moreover, no character is especially likable, though Portia and others have enough dimensions to make them interesting. It falls on the adapters and performers to make sense of bizarre motives and irrational hatred. Now at the Shakespeare Theatre, director Ethan McSweeny and his cast are thoughtful enough to imbue the play with the passion and wit it requires. Some situations are more thoughtfully handled than others, but the first-rate production and a storytelling masterstroke are a substitute for the occasional lapse of nuance.