The question of the nature and validity of the vow of chastity itself was central to the sixteenth-century debate on the necessity and value of clerical celibacy. Catholic writers before and during the Reformation defended both the validity of monastic vows in general, and that of chastity in particular. The issue at stake was not only whether vows should be kept, but whether it was possible for man to merit his salvation by making such promises. It was not denied that chastity was a difficult state to maintain; rather the emphasis was placed upon its efficacy in the salvation of the individual, and the promise of God that He would provide for those who called upon Him. The promise of celibacy demanded of the clergy fitted them for their priestly and sacrificial function. Since priests were expected to live a life that approached the heavenly, it could not be argued that this manner of life was readily obtainable by all. To achieve such perfection was regarded as a sign of the divine favour that separated the priest from the laity.