James Ussher (1581-1656), one of the most important religious scholars and Protestant leaders of the seventeenth century, helped shape the Church of Ireland and solidify its national identity. In Catholicity and the Covenant of Works, Harrison Perkins addresses the development of Christian doctrine in the Reformed tradition, paying particular attention to the ways in which Ussher adopted various ideas from the broad Christian tradition to shape his doctrine of the covenant of works, which he utilized to explain how God related to humanity both before and after the fall into sin.

Perkins highlights the ecumenical premises that underscored Reformed doctrine and the major role that Ussher played in codifying this doctrine, while also shedding light on the differing perspectives of the established churches of Ireland and England. Catholicity and the Covenant of Works considers how Ussher developed the doctrine of a covenant between God and Adam that was based on law, and illustrates how he related the covenant of works to the doctrines of predestination, Christology, and salvation.