On returning to Leipzig in 1686, he published anonymously two years later his first work, "Scriptorum recentiorum decas", an attack on ten writers of the day. His "Decas Decadum, sive plagiariorum et pseudonymorum centuria" (1689) is the only one of his works to which he signs the name Faber. Fabricius then applied himself to the study of medicine, which, however, he relinquished for that of theology; and having gone to Hamburg in 1693, he proposed to travel abroad, when the unexpected tidings that the expense of his education had absorbed his whole patrimony, and even left him in debt to his trustee, forced him to abandon this project. In 1693 he published a doctoral dissertation "De Platonismo Philonis Judaei" which contributed to Philo of Alexandria's losing his position as an "honorary Church Father".