This article aims to provide a social, as opposed to a strictly religious, context for Jesuit missionary mobility at the beginning of the 17th century. It is focused on Milan, capital of the Catholic reformation and a strategic place for the Spanish Habsburg monarchy. It uses Indipetae letters, written by Jesuits applying for a mission, their life stor ies, and focuses on the case of the correspondence between a missionar y in Paraguay and the archbishop Federico Borromeo. While knowledge about the foreign missions reaches the European public of the cities in various ways, the departure of missionaries is clouded in myth and uncertainty. The widespread desire to go to the Indies among the youth paves the way for the decision to join a religious order. While only a few actually proceed to a mission, this movement indicates that the whole society can be said to consent to the catholic missionary movement out of Europe.