The Prophet of Islam — born in Mecca around 570 CE, a merchant who received revelations he identified as the word of God, who united the Arabian Peninsula under a new monotheism, and whose life, teaching, and example became the foundation of a civilization that at its height stretched from Spain to Central Asia and remains a living force for 1.8 billion people — and a figure whose historical reconstruction is entangled with theological commitment in ways that make him one of the most studied and most contested persons in history.
Muhammad is the most influential person in history who left no written record. Everything we know about him comes from sources compiled generations after his death, by communities with strong reasons to present him in specific ways. The Quran — which Muslims hold to be God's word, not Muhammad's — was assembled into canonical form under the third Caliph. The hadiths — reports of his sayings and deeds — were compiled in the 9th century, two hundred years after his death, by scholars who were simultaneously doing history and theology. The historical Muhammad and the theological Muhammad cannot be fully separated, and the attempt to do so is itself a contested act.