In Western Christian theology, grace has been defined, not as a created substance of any kind, but as "the love and mercy given to us by God because God desires us to have it, not necessarily because of anything we have done to earn it", "the condescension or benevolence shown by God toward the human race". It is understood by Christians to be a spontaneous gift from God to people "generous, free and totally unexpected and undeserved" – that takes the form of divine favor, love, clemency, and a share in the divine life of God.
It is an attribute of God that is most manifest in the salvation of sinners. Christian orthodoxy holds that the initiative in the relationship of grace between God and an individual is always on the side of God.
In Eastern Christianity too, grace is the working of God completely, not a created substance of any kind that can be treated like a commodity.
The question of the means of grace has been called "the watershed that divides Catholicism from Protestantism, Calvinism from Arminianism, modern [theological] liberalism from [theological] conservatism." The Catholic Church holds that it is because of the action of Christ and the Holy Spirit in transforming into the divine life what is subjected to God's power that "the sacraments confer the grace they signify": "the power of Christ and his Spirit acts in and through [each sacrament], independently of the personal holiness of the minister. Nevertheless, the fruits of the sacraments also depend on the disposition of the one who receives them." the Sacred Mysteries (sacraments) are seen as a means of partaking of divine grace because God works through his Church. Catholics, Eastern Orthodox and Protestants agree that faith is a gift from God. Ephesians 2:8; "For by grace you have been saved through faith, and that not of yourselves; it is the gift of God". Protestants almost universally believe that grace is given by God based on the faith of the believer. Lutherans hold that the means of grace are "the gospel in Word and sacraments". That the sacraments are means of grace is also the teaching of John Wesley, who described the Eucharist as "the grand channel whereby the grace of his Spirit was conveyed to the souls of all the children of God". Calvinists emphasize "the utter helplessness of <people>apart from grace." But God reaches out with "first grace" or "prevenient grace" that each person may accept or reject. The Calvinist doctrine known as irresistible grace states that, since all persons are by nature spiritually dead, no one desires to accept this grace until God spiritually enlivens them by means of regeneration. God regenerates only individuals whom he has predestined to salvation. Arminians understand the grace of God as cooperating with one's free will in order to bring an individual to salvation. According to Evangelical theologian Charles C. Ryrie, modern liberal theology "gives an exaggerated place to the abilities of people to decide their own fate and to effect their own salvation entirely apart from God's grace." He writes that theological conservatives maintain God's grace is necessary for salvation.