In 1776 he was removed to Schwächat to go through a course of Moral Theology. His disgust at his enforced studies, which he regarded as the thrashing of empty husks, increased. He was angry at his removal from the friends he had made at Wardein. Vexation, irritation, doubt, threw him into a fever, and he was transferred to the convent in the suburbs of Vienna, where he could be under better medical care. The physician who attended him soon saw that his patient's malady was mental. Fessler opened his heart to him, and begged for the loan of books more feeding to the brain than the mystical rubbish in the convent library. The doctor advised him to visit him, when discharged as cured from the convent infirmary, instead of at once returning to Schwächat. This he did, and the doctor introduced him to two men of eminence and influence, Von Eybel and the prelate Rautenstrauch, a Benedictine abbot, the director of the Theological Faculties in the Austrian Monarchy. This latter promised Fessler to assist him in his studies, and urged him to study Greek and Hebrew, also to widen the circle of his reading, to make acquaintance with law, history, with natural science and geography, and undertook to provide him with the requisite books. On his return to Schwächat, Fessler appealed to the Provincial against his Master of Studies whom he pronounced to be an incompetent pedant. At his request he was moved to Wiener-Neustadt. There he found the lecturer on Ecclesiastical Studies as superficial as the man from whom he had escaped. This man did not object to Fessler pursuing his Greek and Hebrew studies, nor to his taking from the library what books he liked. The young candidate now borrowed and devoured deistical works, Hobbes, Tindal, Edelmann, and the Wolfenbüttel Fragments. He had to be careful not to let these books be seen, accordingly he hid them under the floor in the choir. After midnight, when matins had been sung, instead of returning to bed with the rest, he remained, on the plea of devotion, in the church, seated on the altar steps, reading deistical works by the light of the sanctuary lamp, which he pulled down to a proper level. He now completely lost his faith, not in Christianity only, but in natural religion as well. Nevertheless, he did not desist from his purpose of seeking orders. He was ordained deacon in 1778, and priest in 1779. "On the Sunday after Corpus Christi, I celebrated without faith, without unction, my first mass, in the presence of my mother, her brother, and the rest of my family. They all received the communion from my hand, bathed in tears of emotion. I, who administered to them, was frozen in unbelief."