The five pillars are what a Muslim does; the six articles are what a Muslim holds. They come from the hadith of Jibril, in which a stranger in white with no dust of travel on him sits knee to knee with the Prophet and asks three questions — what is islam, what is iman, what is ihsan — and confirms each answer, then leaves. The Prophet tells his companions that was Jibril, come to teach you your religion. Sunni catechisms have been built on that structure ever since. The sixth article, qadar, is the one that carries the doctrinal weight: it is the ground of the freedom argument that has never been settled. Twelver Shia use a different list of five roots — divine unity, justice, prophecy, imamate, resurrection — which puts God's justice and the imamate at the level of creed rather than of law.