The Sunni-Shia split is political in origin, not theological.

Evidence

Shi ite and Sunni Muslims share the same basic beliefs in the unity of God, the apostolate of Muhammad, the finality and perfection of the Qur’anic reve­ lation, and the principles and obligations of the holy law. Apart from the crucial issue of the imamate, there are no major theological differences between them, and only relatively minor differences of ritual and law—though the latter, in such social matters as marriage and inheritance, may at times acquire a dispro­ portionate significance. There is thus no meaning to the parallels that are some­ times drawn between the Sunni-Shi a cleavage in Islam and the schisms and heresies that have riven the world of Christendom. The original difference in Islam was political, concerning candidates for office. But in the course of the centuries, as the two main groups grew apart, other differences arose, the most important of which were psychological and emotional—the differences of mood and direction resulting from their greatly different experience. This is true not only of the differences between Sunni and Shi ite Muslims, but also of the many disagreements that arose among the Shi a themselves, dividing them into in­ numerable schools and sects. Here too the differences were in origin political— about which of several claimants was the rightful imam, the rightful head of Shi ite and ultimately of all Islam. And here again, in the course of time, other differences—in belief and practice, in tactics and strategy—were added. — Bernard Lewis, From Babel to Dragomans, 1452

Categorization

• XREF: Complicates Christian-schism analogies often used in Western commentary on Sunni-Shia conflict; relates to the reader’s Said-adjacent cluster on how Western frameworks misread Islam. — connects to: The religious-freedom debates were not a Christian-Muslim clash but split Muslim delegates too.; The Sunni-Shi’a split originated from political succession struggles — Deepa Kumar, Islamophobia and the Politics of…, 317; The Sunni-Shi’a split originated from political succession struggle, not theology.
• SEED: Angle: the rhetorical habit of mapping Islamic divisions onto Christian heresy vocabulary as a subtle Orientalist move — how the analogy smuggles in theological assumptions the Muslim divide never had.
• corroborated: 2 independent passages support this claim — Bernard Lewis, From Babel to Dragomans: Interpreting…, 1452