Modern Orthodoxy is a form of American Judaism that affirms the traditional tenets and practices of Orthodox Judaism while at the same time maintaining an openness to contemporary cultural and intellectual developments. Beginning in the post-World War II era, Living in Both Worlds shows how a fledgling Modern Orthodoxy carved out an identity separate and apart from unacculturated ultra-Orthodoxy to its right and Conservative Judaism to its left, and follows its development through the first quarter of the twenty-first century as new, divisive issues such as feminism, LGBTQ rights, and the spread of academic biblical scholarship challenged its coherence, and a rejuvenated ultra-Orthodoxy contested its religious legitimacy.