Church division constitutes a grave sin

Church division constitutes a grave sin because it ruptures the fundamental spiritual reality that defines Christian identity. According to Thomas Aquinas, schism is a special sin precisely because it involves the deliberate intention to separate from the communion of love that unites the entire Church through the Holy Spirit.[1] This isn’t merely an organizational or administrative matter—it strikes at the heart of what the Church is meant to be.

Scripture depicts believers as members of a single body animated by one Spirit, creating a supernatural unity that transcends individual identity.[2] When division occurs, this organic wholeness fractures. Schism represents the breaking of ecclesial communion itself.[1] The severity lies not in disagreement over secondary matters, but in the act of severing fellowship and establishing rival communities that deny the other’s legitimacy.

The gravity intensifies because division typically stems from motives that contradict Christian virtue. The early Church identified “lust for power” as a primary cause of schism.[1] More broadly, schism emerges from personal pride, political ambitions, and the insistence on one’s own will rather than submission to the body’s unity.[1] Proverbs identifies “one who sows discord among brethren” as something the Lord abhors—schism is an abomination.[3]

Importantly, even when doctrinal disputes arise, Augustine maintains that schism remains sinful, though it may sometimes represent the lesser of two evils.[4] The Church’s unity reflects Christ’s own prayer and mission, making its fracture a wound against His body and a scandal to the world.

Jesus prayed that believers “may be one” so that the world would believe He was sent by the Father. (John 17:20–23) Paul’s rhetorical question—“Is Christ divided?”—captures the fundamental absurdity and offense of schism. (1 Cor 1:10–13)

[1] Johann Auer, The Church: The Universal Sacrament of Salvation, ed. Hugh M. Riley, Johann Auer, and Joseph Ratzinger, trans. Michael Waldstein, Dogmatic Theology (Washington, D.C.: The Catholic University of America Press, 1993), 8:398.
[2] Sereno D. Clark, “Free Communion,” Bibliotheca Sacra (1867), 494.
[3] Terence Peter Crosby, Opening up 2 and 3 John, Opening Up Commentary (Leominster: Day One Publications, 2006), 70.
[4] Graham Tomlin, Navigating a World of Grace: The Promise of Generous Orthodoxy (London, United Kingdom: SPCK Publishing, 2022). [See here.]