[2] In 1776, at the age of sixteen, on the recommendation of James Butler, Archbishop of Cashel, Lanigan received a burse to study at the Irish College at Rome.
He sailed from Cork to London, where he was robbed of his money by a fellow-passenger; but fortunately a priest afforded him a refuge in his house until a remittance from home enabled him to continue his journey to Rome.
By the advice of Pietro Tamburini, an open supporter of Jasenism, he left Rome and accepted the chair of ecclesiastical history and Hebrew in the University of Pavia,[5] where he worked as a professor from 1789 to 1796.
[7] In 1793 he published his Institutionum biblicarum pars prima (Pavia), a learned work concerning the history of the books of the Old and New Testaments; the two other parts which he had planned were not written.
After an unsuccessful attempt for an appointment to a parish in his home diocese, he wandered on to Dublin, where he was taken in as an assistant priest at the old Francis Street Chapel, by the vicar-general, Father Hamil, a fellow student of his Roman days.
Dr. Moylan, however, raised difficulties; he proposed that Lanigan should first sign a formula used to test the Catholicity of the numerous French clergy who were taking refuge in Ireland at that time.
[5] Through the influence of Charles Vallancey, Lanigan found work as a sub-editor at the Royal Dublin Society, translating, cataloguing, and proof-reading.
After a few years, he was appointed assistant librarian and began to work on his Ecclesiastical History of Ireland from the first introduction of Christianity among the Irish to the beginning of the thirteenth century, which was not, however, published till 1822 (4 vols., 8vo, Dublin).
He wrote frequently to the Press in favour of religious equality for Catholics, and fought vigorously against the proposed Royal Veto in connection with Irish episcopal elections.
[8] In 1813 his health began to fail, and he was granted a leave of absence to return to his home at Cashel, where he was tended by his sisters; he recovered sufficiently to resume his duties in Dublin.