Though forged in the fires of the early nineteenth-century evangelical revivals, Primitive Baptists became the most significant opponents of the burgeoning antebellum evangelical movement. The Primitives were Calvinists who despised missionaries, Sunday schools, Bible tract societies, and the other accoutrements of evangelical Protestantism. This article contends that a feeling of uncertainty dominated Primitive Baptists' lives, catalyzed their movement's rise, and fueled their strident opposition to the theological and organizational changes shaping churches across the country. For Primitive Baptists, it was their questioning–especially their experience of persistent doubt–that set them apart from evangelicals. The uncertainty that colored Primitive Baptist selfhood motivated believers rather than paralyzed them. It propelled them toward a community of like-minded souls, and it stirred those souls to action as a more ardent brand of evangelical Protestantism crowded church pews. It is in the Primitives' uncertain selves–not in their theology or their socio-economic condition–that we find the most compelling explanation of their movement's unlikely rise.