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.
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.
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!"
[2] Says Spaeth: "From those words I understood the 53d chapter of Isaiah: the Jews bore the sins of the heathen, while they were daily persecuted by them.