815. The sin of unbelief is, committed either directly or indirectly. (a) It is committed directly, when one rejects what pertains to faith (its acts, objects or motive); (b) it is committed indirectly, when one guiltily places oneself or others in the occasion or danger of unbelief. The dangers against faith will be considered after the sins of unbelief (see 848-886).
816. Direct sins of unbelief are those opposed to the elements that belong to the nature of faith and that are contained in its definition (see 751, 798). (a) Opposed to the act of assent are sins of non-assent or dissent (see 817-839); (b) opposed to the certitude and firmness of assent are sins of doubt (840-846); (c) opposed to the right object of faith are sins of credulity (847); (d) opposed to the motive of faith is rationalism (847).
817. Sins of non-assent are those by which one omits to make an act of faith when one should. This kind of sin will be treated when we come to the commandments of faith as to its internal and external acts (see 925 sqq.)
818. Sins of dissent are sins of commission, and are of two kinds: (a) privative unbelief, which is the want of faith in one who has heard the faith sufficiently and should realize the obligation of embracing it, but who refuses to believe, although he makes no opposition to faith; (b) contrary unbelief, which is the want of faith in one who has heard the faith and its motives of credibility sufficiently to know the duty of embracing it, and who not only refuses to believe, but even accepts the errors opposed to faith.
819. What is the gravity of sins of dissent, doubt, and rationalism? (a) From their nature, these sins are always mortal, for they refuse to God the homage of the intellect and will that is due Him, deprive man of the beginning of spiritual life, and lead to eternal condemnation (Mark, xvi. 16). (b) From their circumstances, these and other sins against faith may be venial (see 180-184). Thus, if a man refuses to believe or accepts error, not having sufficient knowledge of his obligation or not fully consenting to the sin, his fault is venial subjectively or formally.
820. Are sins against faith more serious than all other kinds of sin? (a) From their nature, sins against faith are worse than sins against the moral virtues, for the former offend directly against God Himself, but not so the latter. Hatred of God, however, is a greater sin than sins of unbelief, as will be shown when we treat of sins against charity. (b) From their circumstances, sins against faith may be less serious than sins against the moral virtues. Example: A venial sin against faith is less serious than a mortal sin against justice.
821. With regard to the effect of sins against faith on good acts it should be noted: (a) an unbeliever is able to perform works that are ethically or naturally good (Rom., ii. 14), and the Church has condemned the opposite teaching of Baius (Denzinger, _Enchiridion_, n. 1025). (b) an unbeliever is not able to perform works that are supernaturally good and meritorious (see 112).
822. Contrary unbelief (see 818), which not only refuses to believe but also assents to contrary errors, has three degrees according to the greater or less number of truths denied or errors admitted in these three degrees. Some theologians see different species of unbelief, while other theologians regard them as only accidental modes or circumstances of the one species of sin.
(a) The most extensive denial of faith is found in infidelity, which rejects both Christ and His revelation. To this form of unbelief belong atheism, agnosticism, pantheism, paganism, polytheism, animism, and denials of Christ and Christianity. The chief religious bodies today that profess such errors are: Confucianism, Taoism and Shintoism (founded in China and Japan), which are polytheistic and practise idolatry and ancestor worship; Brahmanism (founded about 14 centuries before Christ), which is polytheistic or animistic: Buddhism (founded 6th century B.C. in India), which is polytheistic and practises idolatry; Zoroastrianism (founded in Persia about the 7th century B.C.), which is dualistic; Mohammedanism (founded in Arabia in the 6th century A.D.), which makes Mohammed and his religion superior to Christ and Christianity, and rejects the Trinity and the Incarnation. (b) A less complete departure from faith is found when Christ and His revelation are accepted as contained in the figures and prophecies of the Old Testament, but rejected in their fulfillment and development in Jesus and the New Testament. This is the error of Judaism, which today has about 15 million adherents.
(c) A still smaller degree of rejection of faith exists when Christ is recognized as leader and teacher, but not all of His revelation is accepted. This kind of error is called heresy, and those bodies which profess it are known as sects. The chief heresies in times past were Gnosticism and Manicheism in the first centuries; Arianism and Macedonianism in the fourth century; Nestorianism, Monophysism and Pelagianism in the fifth century; Monothelism in the seventh century; Iconoclasm in the eighth century; Photianism in the ninth century; Albigensianism in the eleventh century; Waldensianism in the twelfth century; Wicliffism in the fourteenth century; Hussism in the fifteenth century; Protestantism in the sixteenth century, and Modernism in the twentieth century. Today, the erring Christian groups outside the Church are the Orientals, called Orthodox, and the Protestants.