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.
In 1683 Spaeth reconverted to Catholicism, which he fervently advocated for and praised in a treatise titled Judicium Amoris de Fundamentalibus Quibusdam, Qui Feruntur Erroribus Ecclesiæ Romanæ. Nonetheless, this reconciliation was brief.