In his youth he had vowed to consecrate his life to the conversion of the African slaves and native Indians of his adopted country, and arriving in Maranhão early in 1653 he recommenced his apostolic labors, which had been interrupted during his stay of fourteen years in the Old World. Starting from Pará, he penetrated to the banks of the Tocantins, making numerous converts to Christianity and European civilization among the most violent tribes; but after two years of unceasing labour, during which every difficulty was placed in his way by the colonial authorities, he saw that the Indians must be withdrawn from the jurisdiction of the governors, to prevent their exploitation, and placed under the control of the members of a single religious society.