Sinless

Impeccability is the absence of sin. Christianity teaches this to be an attribute of God (logically God cannot sin, it would mean that he would act against his own will and nature) and therefore it is also commonly, but not uncontroversially, attributed to Christ.

Early Christians questioned whether the victorious saints in heaven could sin. The widely influential Eastern Church Father and theologian Origen of Alexandria maintained that they could. Official Roman Catholic doctrine holds that they cannot. Although Catholics believe in the gift of free will, saints in heaven already see God face to face and are incapable of sinning (see Pope Benedict XII and beatific vision), i.e., they will necessarily remain in God. The Catechism of the Catholic Church states (emphasis added):

1045 For man, this consummation will be the final realization of the unity of the human race, which God willed from creation and of which the pilgrim Church has been "in the nature of sacrament." Those who are united with Christ will form the community of the redeemed, "the holy city" of God, "the Bride, the wife of the Lamb." She will not be wounded any longer by sin, stains, self-love, that destroy or wound the earthly community. The beatific vision, in which God opens himself in an inexhaustible way to the elect, will be the ever-flowing well-spring of happiness, peace, and mutual communion.

1060 At the end of time, the Kingdom of God will come in its fullness. Then the just will reign with Christ for ever, glorified in body and soul, and the material universe itself will be transformed. God will then be "all in all" (⇒ 1 Cor 15:28), in eternal life.

The 13th-century, Dominican theologian Thomas Aquinas taught that souls in Purgatory cannot sin (Summa Theologica, Second Part of the Second Part, Question 83, Article 11, Reply to Objection 3), let alone the saints in heaven. This is the teaching of the Roman Catholic Church, although there are different opinions on the reasons for the impossibility to sin.

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