We must now consider the vices contrary to peace, which belong to deeds: such are schism, strife, sedition, and war. In the first place, then, about schism, there are four points of inquiry:
(1) Whether schism is a special sin?
(2) Whether it is graver than unbelief?
(3) Of the power exercised by schismatics;
(4) Of the punishment inflicted on them. _______________________
FIRST ARTICLE [II-II, Q. 39, Art. 1]
Whether Schism Is a Special Sin?
Objection 1: It would seem that schism is not a special sin. For "schism," as Pope Pelagius I says (Epist. ad Victor. et Pancrat.), "denotes a division." But every sin causes a division, according to Isa. 59: "Your sins have divided between you and your God." Therefore schism is not a special sin.
Obj. 2: Further, a man is apparently a schismatic if he disobeys the Church. But every sin makes a man disobey the commandments of the Church, because sin, according to Ambrose (De Parad. viii) "is disobedience against the heavenly commandments." Therefore every sin is a schism.
Obj. 3: Further, heresy also divides a man from the unity of faith. If, therefore, the word schism denotes a division, it would seem not to differ, as a special sin, from the sin of unbelief.