The fourth century saw greater refinement in the differentiation of clergy beyond the three-fold ministry of the second century. (Ferguson, 211)
The bishop became more of an administrator, and the local pastoral care and liturgical leadership passed to presbyters. (Ibid.)
The influence of Ambrose, Jerome, and Augustine made celibacy virtually obligatory in the West on all clerics in major orders. Increasingly in the fourth and fifth centuries bishops were chosen from among the monks, in both East and West, and under Justinian celibacy was imposed on bishops in the East. (Ibid., 212)
The thinkers and writers of this period—especially Augustine in the Latin West and the three Cappadocians (Basil, Gregory of Nazianzus, and Gregory of Nyssa) in the Greek East—laid the intellectual foundations for the Christianization of classical culture. (Ibid.)
