(clerics regular) which in the modern sense are a category of priests of male religious orders constituted from the 16th century, examples being the Theatines or the Barnabites. The members of these orders are for the greater part priests who take religious vows and have an active apostolic life. While they live in communities, they belong to the order as such rather than to a particular house and their prime focus is on pastoral work rather than a choral office. Background According to St. Thomas Aquinas, a canon regular is essentially a religious cleric; "The Order of Canons Regular is necessarily constituted by religious clerics, because they are essentially destined to those works which relate to the Divine mysteries, whereas it is not so with the monastic Orders." This is what constitutes a canon regular and what distinguishes him from a monk. The clerical state is essential to the Order of Canons Regular, whereas it is only accidental to the Monastic Order. Erasmus, himself a canon regular, declared that the canons regular are a "median point" between the monks and the secular clergy. The outer appearance and observances of the canons regular can seem very similar to those of the monks. This is because the various reforms borrowed certain practices from the monks for the use of the canons. According to St. Augustine, a canon regular professes two things, "sanctitatem et clericatum". He lives in community, he leads the life of a religious, he sings the praises of God by the daily recitation of the Divine Office in choir; but at the same time, at the bidding of his superiors, he is prepared to follow the example of the Apostles by preaching, teaching, and the administration of the sacraments, or by giving hospitality to pilgrims and travellers, and tending the sick. In fact, traditionally canons regular have not confined themselves exclusively to the functions of the canonical life. They have also given hospitality to pilgrims and travelers on the Great St. Bernard and on the Simplon, and in former times the hospitals of St. Bartholomew's Smithfield, in London, of Santo Spirito, in Rome, of Lochleven, Monymusk and St. Andrew's, in Scotland, and others like them, were all served by canons regular. Many houses of canons worked among the poor, the lepers, and the infirm. The clerics established by St. Patrick in Ireland had accommodation for pilgrims and the sick whom