Two European missionary teams, one Catholic and the other Protestant, encountered each other in the Tamil country in the first decade of the eighteenth century. They acted as if and thought that their goals were irreconcilable, even if the Protestants in Tranquebar admitted that the Catholic Jesuit proselytism in the region had been efficient as “preparatio evangelicae” for the Protestant mission. Jesuits and Pietists were not only rivals; they also collaborated, uneasily and unequally, in collecting, processing, and disseminating knowledge. Missionary linguistic and medico-botanical expertise was considered an indispensable proselytizing tool, and it showcased their “scientific” achievements that were admired and envied in Europe. Both Pietists and Jesuits of this period were fighting the early Enlightenment atheists while feeding them the materials from the missions. Both missionary groups were also victims of Enlightenment historiography. Despite their theological differences, they were far closer in their practices than either the missionaries themselves or their historians, who have mostly written from the same denominational perspective, have been willing to acknowledge. In part this was because the Protestants, especially their mission's founders, relied on both texts and converts produced by their Catholic rivals.