The Three Forms of Unity

The Heidelberg Catechism did not stay a regional teaching document. Dutch Reformed synods adopted it during the long conflict with Spain, and the Synod of Dort formally confirmed it in 1618 and 1619 alongside the Belgic Confession and the canons the synod itself produced against the Arminian Remonstrance, binding the three together as what Dutch Reformed tradition calls the Three Forms of Unity.

Office bearers, ministers, elders and deacons in churches descending from that tradition subscribe to all three as a unit, so the catechism functions less as an optional teaching aid than as one leg of a confessional standard alongside two documents in a different genre altogether, a confession of articles and a set of conciliar canons. Its reach followed Dutch emigration far beyond the Netherlands, into Reformed churches in North America, South Africa and Indonesia, and it remains in active use for catechetical preaching in congregations that keep the old fifty-two Sunday cycle. Its standing among the three forms has not stopped it from being the most read of them on its own merits. Where the Belgic Confession and the Canons of Dort are consulted mainly by office bearers and students of doctrine, the Heidelberg Catechism's first answer is quoted in ordinary Reformed devotion far more often than any sentence from its two formal companions.