He studied philosophy and Lutheran theology at Tübingen (1722-1728), and was impressed by the works of Jakob Böhme, and also devoted attention to Leibniz and Wolff.
During his travels, in his eager search for knowledge, he made the acquaintance of mystics and separatists, Christians and learned Jews, theologians and physicians alike.
The Philadelphians influenced him to accept apocatastasis, the belief that all people would eventually be saved; he wove this into his theological system, depending chiefly upon I Corinthians 15 and Ephesians 1:9-11.
“My religion,” he once said, “is the parallelism of Nature and Grace.” Oetinger translated a part of Emanuel Swedenborg's philosophy of heaven and earth, and added notes of his own.
This and his translations of Swedenborg brought upon him the censure of his ecclesiastical superiors, but he was protected by the Duke of Württemberg, and later was appointed superintendent of the churches in the district of Weinsberg.