Johann Peter Spaeth

Johann Peter Spaeth, also known as Moses Germanus or Moses Ashkenazi (1st half of the 17th century in Vienna – April 27, 1701 in Amsterdam) was an Austrian theologian that converted to Judaism.
Lutheran convert.
Amid rumors of impending war, his father, a poor shoemaker, sought refuge between 1642 and 1645 at Augsburg. He was a pious Roman Catholic, and confided his son Peter to the Jesuits for his education. Spaeth later went to Vienna and earned his living as a private tutor. Becoming dissatisfied with Catholic dogma, he embraced Lutheranism (1680). On that occasion he wrote his first work: "Εκιαγραφια, Theologico-Philosophico Ænigmatica". The work found much favor with M. Spitzel, head of the board of theological studies at Augsburg, who recommended Spaeth to many influential personages in Strassburg and afterward to others in Frankfort-on-the-Main.
In 1683 Spaeth returned to Catholicism, which he defended and praised in a work entitled "Judicium Amoris de Fundamentalibus Quibusdam, Qui Feruntur Erroribus Ecclesiæ Romanæ". But this reconciliation did not last. New doubts assailed his mind; and after having mingled with the members of certain dissident sects, such as the Socinians and Mennonites, and after having taken up the study of Hebrew literature and the cabalistic writings, he renounced Christianity and vehemently attacked it. Even the Sermon on the Mount, as requiring an impossible ideality, did not escape his criticism. As for the Christian writings other than the New Testament, he held that until Constantine I founded Christianity they were all drawn from Jewish tradition.
Convert to Judaism.
It seems that Spaeth did not intend to become a proselyte to Judaism, and that his conversion was brought about, as he himself relates, through the following incident: Once a crucifix dropped from his pocket, and it was picked up by a Jew, who said: "It is Israel, the man of sorrow!" Says Spaeth:
Spaeth became converted at Cleves, taking the name "Moses Germanus".
Literary works.
Besides the above-mentioned works, Moses published the following: