those who are born again are members of the New Covenant. History Concepts foundational to covenant theology can be found in the writings of Church Fathers such as Irenaeus and Augustine. Huldrych Zwingli and Johannes Oecolampadius were among the first reformers to speak of God's salvation economy under the categories of a covenant of works and a covenant of grace. John Calvin (Institutes 2:9–11), like Heinrich Bullinger (A Brief Exposition of the One and Eternal Testament or Covenant of God), focused on the continuity of the covenant of grace, but taught the substance of what became classic covenant theology in terms of Law and Gospel. Early post-reformation writings, including Zacharius Ursinus (1534–83) in Commentary on the Heidelberg Catechism (published posthumously, 1591), Caspar Olevianus (1536–87) in Concerning the Substance of the Covenant of Grace between God and the Elect (De substantia foederis gratuiti inter deum et electos, 1585), and Scottish Theologian Robert Rollock (1555–99) in A Treatise of our Effectual Calling (Tractatus de vocatione efficaci, 1597), developed the covenant of works and covenant of grace scheme along the lines of the law-gospel distinction. Classical statements of covenant theology can be found in the British Westminster Confession of Faith (particularly chap. 7, 8, 19), as well as in the writings of English theologians such as John Owen (1616–83), Biblical Theology, and An Exposition of the Epistle to the Hebrews. The classical statements among 17th century continental theologians include Johannes Cocceius (c. 1603–69) in The Doctrine of the Covenant and Testament of God (Summa doctrinae de foedere et testamento dei, 1648), Francis Turretin (1623–87) in his Institutes of Elenctic Theology, and Hermann Witsius (1636–1708) in The Economy of the Covenants Between God and Man. It may also be seen in the writings of Jonathan Edwards (1703–58) in Collected Writings of Jonathan Edwards, Vol 2, Banner of Truth edition, p. 950. In the United States, the Princeton theologians (Charles Hodge, A.A. Hodge, B.B. Warfield, Geerhardus Vos, and J. Gresham Machen) and, in the Netherlands, Herman Bavinck followed the main lines of the classic view, teaching the Covenant of Redemption, the Covenant of Works (Law), and the Covenant of Grace (Gospel). Recent well-known covenant theologians in the United States include Michael Horton, J. Ligon Duncan III, Meredith G. Kline, J.I. Packer, Richard L. Pratt Jr., O. Palmer Robertson and R.C. Sproul. This system is taught at schools such as Covenant Theological Seminary, Greenville Presbyterian Theological