Prize-winning scholar Nussbaum argues that opera engages in political thought, conveying moral and philosophical ideas about rights and freedoms, gender, rank, and class. Beyond the libretti, these ideas are expressed in the music itself and in the act of singing. Nussbaum devotes half the book to Mozart, whom she sees as “the deepest philosopher of the Enlightenment,” cognizant of other major thinkers, such as Jean-Jacques Rousseau, Immanuel Kant, and Johann Gottfried von Herder. Mozart was a Freemason, a member of a “quasi-religion, a fraternity based upon ethical commitments,” especially to fostering human dignity. As a Freemason, he was committed to the ideals of freedom, equality, mercy, and fraternal love, as well as to the rejection of religious superstition, class privilege, honor, and revenge. These ideals inform Mozart’s The Marriage of Figaro, The Magic Flute, Idomeneo, Don Giovanni, Così fan tutte, and the lesser-known La clemenza di Tito, operas in which characters commit bad acts motivated by a desire for revenge, but in which mercy and reason prevail. Mozart, Nussbaum asserts, conceived of his operas as political, contributing to the reshaping of human attitudes needed to forge a new public culture. The second half of the book considers operas that further Mozartean themes, including Beethoven’s only opera, Fidelio, “opera’s greatest musical depiction” of hope; Heggie’s Dead Man Walking; Verdi’s Don Carlos, infused with its creator’s “zeal for liberty”; Benjamin Britten’s Peter Grimes and his Albert Herring, dealing with the plight of the outcast; Janacek’s Jenufa; John Adams’ Nixon in China; and Verdi’s Falstaff. These works capture the spirit of optimism and joy that pervades what the author calls “a republicanism of the heart.” In contrast, Nussbaum sees Wagner as the composer whose despair, xenophobic paranoia, and fantasies of cultural purity place him in opposition to Mozartean ideals.