predestination, or the belief God chooses some people for damnation as well as some for salvation. Catholic scholars tend to deny he held such a view while some Protestants and secular scholars have held that Augustine did believe in double predestination. About 412, Augustine became the first Christian to understand predestination as a divine unilateral pre-determination of individuals' eternal destinies independently of human choice, although his prior Manichaean sect did teach this concept. Some Protestant theologians, such as Justo L. González and Bengt Hägglund, interpret Augustine's teaching that grace is irresistible, results in conversion, and leads to perseverance. In On Rebuke and Grace (De correptione et gratia), Augustine wrote: "And what is written, that He wills all men to be saved, while yet all men are not saved, may be understood in many ways, some of which I have mentioned in other writings of mine; but here I will say one thing: He wills all men to be saved, is so said that all the predestinated may be understood by it, because every kind of men is among them." Speaking of the twins Jacob and Esau, Augustine wrote in his book On the Gift of Perseverance, "[I]t ought to be a most certain fact that the former is of the predestinated, the latter is not." Sacramental theology Also in reaction against the Donatists, Augustine developed a distinction between the "regularity" and "validity" of the sacraments. Regular sacraments are performed by clergy of the Catholic Church, while sacraments performed by schismatics are considered irregular. Nevertheless, the validity of the sacraments do not depend upon the holiness of the priests who perform them (ex opere operato); therefore, irregular sacraments are still accepted as valid provided they are done in the name of Christ and in the manner prescribed by the Church. On this point Augustine departs from the earlier teaching of Cyprian, who taught that converts from schismatic movements must be re-baptised. Augustine taught that sacraments administered outside the Catholic Church, though true sacraments, avail nothing. However, he also stated that baptism, while it does not confer any grace when done outside the Church, does confer grace as soon as one is received into the Catholic Church. Augustine is said to have held an understanding of the real presence of Christ in the Eucharist, saying that Christ's statement, "This is my body" referred to the bread he carried in his hands, and