On early American frontiers, Indians and Europeans made new cultures on the basis of what one scholar has termed creative misunderstandings . Unable to fully understand each other, diverse peoples invented a shared culture by appealing to what they thought to be the values and beliefs of the other. But what happened when people actually learned to communicate their true values and beliefs across the frontier? This article focuses on language learning and linguistic exchange among Illinois Indians and Jesuit priests in the Illinois mission over two generations. As a second generation of priests became masters of the Illinois language in the 1690s, allowing more sophisticated intercultural communication in Illinois missions, Illinois Indians and Jesuits moved beyond the initial creative misunderstandings of the encounter and came to a realistic assessment of their differences. The ironic result of better communication was the end of an optimistic era of religious syncretism in this most remote Jesuit mission in North America.