Over the past decade, theoretical debates in the anthropology of religion have made few references to Jewish case studies. In contrast, research on Islam has heavily, and productively, influenced the field. The most influential of this work has focused on the very devout—religious activists, piety movements, and the newly religious. Recently, though, scholars have questioned whether this focus skews our sense of the lives of religious subjects. The analytical focus on religious activists, critics contend, obscures the dynamics of ambiguity, openness and indeterminacy that irrevocably shape peoples’ lives. It is with this critique in mind, I argue, that the anthropology of Jews and Judaism can contribute to broader debates in the anthropology of religion. In this paper, I foreground the dynamics of ambiguity, openness and indeterminacy in religious observance by looking not at religious activists, but Yiddish language and culture activists, or “Yiddishists.” Drawing on ethnographic research conducted in New York, I focus on the relationship between people’s engagement with Yiddish and their—real and potential—engagement with observant Judaism. For a number of people with whom I worked, ambivalence, about religious practice, and indeterminacy, about what their engagements with Yiddish might mean for the religiosity of their current and future selves, structured their encounters with the Yiddish language and with other Yiddish speaking communities. Focusing on the place of religious observance in the lives of language and culture activists, I ultimately contend, offers one way Jewish studies scholars can bring dynamics of ambivalence and indeterminacy into the cross-cultural analysis of religion.