grace, in Christian theology, the free favor of God toward humans, which is necessary for their salvation. A distinction is made between natural grace (e.g., the gift of life) and supernatural grace, by which God makes a person (born sinful because of original sin) capable of enjoying eternal life. In general, the term grace is restricted to supernatural grace, usually considered as the keystone of the whole Christian theological system.
Supernatural grace is usually defined as being actual or sanctifying. Actual grace turns the soul to God; sanctifying grace confirms and perpetuates the ends of this conversion and makes the soul habitually good. Most theologies (except in Calvinism), wishing to maintain humanity's freedom in addition to God's complete freedom in granting grace, distinguish prevenient grace, which frees a person and awakens him or her to God's call, from cooperating grace, by which God assists to salvation the free person who seeks it.
When God seems to confer on a person such actual grace that his or her conversion appears inevitable, the grace is said to be efficacious. The apparent difficulty of claiming that grace may be efficacious while a person is free was explained by St. Thomas Aquinas on the ground that it was a peculiar nature of this grace granted to some people that it should be ineluctable; it was this doctrine that Luis Molina and the Molinists disputed. Differing in effect from efficacious grace is merely sufficient grace, which, while sufficient to conversion, may be rejected by a person at will. Calvinism rejects merely sufficient grace, holding instead that grace is irresistible.
In every Christian theology God is considered to grant grace quite freely, since its gift is far greater than any person can merit. As to which persons are offered this grace, there is great difference. The generality hold that it is offered to people who place no obstacle in the way of salvation rather than to those who neglect what ways to grace they have been given; the Jansenists (see Jansen, Cornelis), however, believed that grace was not given outside the church, and the Calvinists hold that it is offered only to those predestined to election.
Sanctifying grace may be said to succeed justification as actual grace precedes it. The operation of sanctifying grace brings holiness to the individual soul. The indwelling of God in the soul and the soul's actual participation in God's nature (in an indefinable manner) are the perfections of sanctifying grace. As to the means, there is a serious cleavage in Christianity, notably in regard to sacramental grace. According to Roman Catholics and Orthodox, the grace accompanying a sacrament is ex opere operato, i.e., by God's ordinance the sacrament actually confers grace, the good disposition of the minister being unimportant and that of the recipient being not always a condition; Protestants hold that the sacraments are ex opere operantis, i.e., the faith of the recipient is all-important, and the sacrament is the sign, not the source of grace.
Certain Christian systems have developed quite different ideas of grace, and Pelagianism has its advocates in liberal 20th-century Protestantism. The great emphasis on grace is a distinction of Christianity. In recent years among orthodox theologians there has been a renewed interest in the theology of grace. Among traditional usages, they distinguish three forms of grace: God's communication of Himself to the Christian soul is grace; the favorable attitude of God toward the soul is grace; the ontological modification of Christian life by God's favor is grace.