Celebrated among the ascetical and mystical writings are: the _Ladder of Paradise_ of St. John Climacus (6th century), the Conferences of Cassian (about 416), the _Libri V de Consideratione_ of St. Bernard (d. 1153). St. Gregory the Great’s _De Cura Pastorali_ is a systematic work of pastoral theology, and is regarded as a classic. (b) The Medieval Period (12th to 16th century).--The method of the moralists of this period differs from that of the Fathers in that the former is systematic and philosophical, and more proximately adapted to the use of confessors. The masterpiece of scientific Moral Theology is of course found in the _Summa Theologica_ of St. Thomas Aquinas (d. 1274). Works of casuistry were composed by St. Raymond of Pennafort (about 1235), by John of Freiburg (d. 1314), by John of Asti (about 1317), by Angelus of Chiavasso (about 1476), by Sylvester Prierias (d. 1523). The _Summa Theologica_ of St. Antoninus of Florence (d. 1459) has been called an inexhaustible storehouse for manuals of casuistry. Among the ascetical writers are: St. Bonaventure, the Seraphic Doctor (d. 1274), John Gerson (d. 1429), John Tauler (d. 1361), Bl. Henry Suso (d. 1366), and Denis the Carthusian (d. 1471). (c) The Modern Period (16th century to the present).--Characteristic of this period are the commentaries written on St. Thomas, the controversies over the systems of conscience, the appearance of numerous manuals and special treatises, and the attention given to changed conditions of society and ecclesiastical discipline. Noteworthy among modern works are: the Commentary on St. Thomas by Cajetan (d. 1534); the writings of Bartholomew de Medina (d. 1581), called the father of moderate Probabilism; the _De Paenitentia_ of Lugo (d. 1660), a handbook that combines speculative and casuistical theology; the _Roman Catechism_, which was issued by the authority of the Council of Trent in 1566; the _Theologia Moralis_ of St. Alphonsus Liguori (d. 1787), a work whose authority is universally recognized; the celebrated treatise on the virtues by Lessius (d. 1623); the classic work of Suarez (d. 1617), _De Religione_; the _Summa Casuum Conscientiae_ of Toletus (d. 1596); the commentaries of Francis de Victoria (d. 1546), which are writings of extraordinary merit. More recent works are so numerous that it is impossible to mention them here. 18. Among the many modern works on Moral Theology which have been published abroad, not a few are in the vernacular--in German, French, Italian, Spanish, etc. While they are not intended to replace the Latin text-books used in seminaries, these are nevertheless a very great help to a fuller knowledge of the matter treated and to a more ready use of it in the work of the ministry.