The Synod (or General Synod) of Ulster is the forerunner of the General Assembly of the Presbyterian Church in Ireland. It comprises all the clergy of the church elected by their respective local presbyteries (or church elders) and a section of the laity.
In 1726, the Synod expels ministers, grouped together as the Synod of Antrim, who refuse to subscribe to the Westminster Confession of Faith. Later there is a further secession by those who, insisting on the sole kingship of Christ, reject the Confession. In 1763 they organise a distinct Reformed Presbyterian Church, and in 1811 establish their own provincial synod. In 1746, some of the more doctrinaire Calvinists withdraw, forming the Secession Synod.
Within the mainline Synod there is a continuing distinction between ‘Old Light‘ supporters of theological orthodoxy and ‘New Light‘ elements more inclined to defer to conscience rather than doctrine. In the first decades of the 19th century, positions harden with New Light ministers adopting a Unitarian or Arian skepticism regarding the doctrine of the Trinity. In 1829, when the leading conservative evangelical, Henry Cooke, succeeds in pressing the General Synod for a firm declaration of Trinitarian belief they withdraw to form their own Remonstrant Synod.
The departure of the latitudinarian party makes possible a reconciliation with the earlier Seceders. Purged of its heterodox elements, in 1840 the Synod of Ulster joins with the Secession Synod to form the General Assembly of the Presbyterian Church in Ireland.