Question I: What kind of sin schism is

The name of SCHISM is derived from the verb scindo (I rend), as St. Bonaventure notes in speculo animae, cap. 1. From this word begins to shine forth what sort of sin Schism is: For schism is a disjunction by which one separates himself from the unity of the Church, as it is a certain mystical body, consisting of the faithful of various conditions as members mutually connected, especially with the Head, the Supreme Pontiff, the Vicar of Christ. So reports St. Bonaventure in declaratione terminorum Theologiae. It is defined more briefly by the Angelic Doctor in the place cited here near the end: Schism is the illicit dissension of those among whom unity ought to exist.

The Fathers insert this, when they say that by Schism a man is separated from the Church, as Jerome says in cap. 3. ad Titum; that the unity of the Church is rent, as Irenaeus says Lib. 4. cap. 43., and Cyprian in Lib. de unitate Ecclesiae.

HOW, however, one rends himself from that unity will be perceived once the reason of the unity of the body of the Church is recognized, which consists in an analogical proportion to offices, and to the unity of the human body, in which the members are various, deputed to various offices: some for working, as the hands; some for seeing, as the eyes; some for speaking, as the tongue, lips, palate, etc. For so in this mystical body some are destined for laboring in holy works; others for seeing and providing; others for speaking, teaching, instructing, etc. Hence the Apostle often expounds the state of the Church with this metaphor in his Epistles, as Rom. 12., 1 Cor. 13., Ephes. 4.

HENCE indeed the reason of Schism appears, which is: refusing to conduct oneself in the manner proposed by the Church, and suitable to oneself, among those working and subject to the Supreme Head, to whose governance the whole body is subject.

I assert, therefore, first, that Schism is a mortal sin.

It is proved by 1 Cor. 1. where the Apostle gravely enjoins: Let there be no schisms among you; for to separate oneself from the unity necessary for salvation is a great sin.

I assert that Schism is a special mortal sin.

It is proved, because by Schism the singular bond of Charity is broken, as the Apostle teaches, 1 Cor. 12., saying: Let there be no schism in the body, but the members should be mutually careful one for another, etc. And Ephes. 4.: Bearing with one another in Charity, careful to keep the unity of the Spirit in the bond of peace. One body, and one Spirit; and below: The whole body, compacted and connected by every joint of administration, according to the operation in the measure of the increase of every member, makes the increase of the body unto the edifying of itself in Charity. See also St. Bonaventure in 4. dist. 13. dub. 4. litt.

THEN it is proved from the Fathers, who say that by Schism Charity and peace are violated; so St. Cyprian Lib. de unitate Ecclesiae, where he offers wondrous things on this matter; Augustine Lib. de fide, et Symbolo, cap. 10. et Lib. 2. de Baptismo contra Donatum, cap. 6.

It is proved third, because each one is bound to will, for himself and his neighbor, that good of Charity, and of peace, and of communion in the same body of the Church.

HENCE you can know that someone can be a Schismatic even if he is not a heretic, if, namely, he separates himself from obedience to the Pontiff whom he nonetheless believes to be the Vicar of Christ. For heresy, besides the scission, adds a perverse dogma, as St. Bonaventure notes in centil. in the place to be cited.

The Fathers recognized this distinction: Chrysostom homil. 11. ad Eph., Augustine de fide, et Symbolo, cap. 10. et Lib. 2. contra Cresconium, cap. 7., Jerome in 3. ad Titum, as St. Bonaventure notes in speculo animae, cap. 1.

MOREOVER this disobedience is not against some simple precept, say, of fasting, but is rebellious disobedience against the very Pastor; as Valencia notes (disp. 3. quaest. 15. puncto 1.), Cajetan (in summa, verbo Schisma.). The Angelic Doctor warns, however (p. p. centil. sect. 26.), that Schism usually leads into heresy, that is, into a heretical dogma; namely, that the Church is not to be obeyed.

There will also be Schism if one separates himself from the members of the Church by refusing to conform himself to the other members in the rites: from which it is clear that even the Pope, should that supposition occur, could become a Schismatic, as Turrecremata notes (lib. 4. summa de Ecclesia, part. 1. cap. 11.), Cajetan (hic, art. 1.), Bannes (ibi), Valencia (loco cit.). This would happen if he excommunicated the whole Church; if he refused to use the ecclesiastical rites, etc. See these Doctors.

MOREOVER I say this would come to pass if the Pontiff were so to behave; for I hold that God will ever stand by with a special providence, lest the person of the Pontiff fall so, just as he has ever stood by, lest any Pontiff fall into heresy or Schism. See the authors cited.