A covenant is a kind of agreement, treaty, or testament, generally binding two parties in a contractual relationship. The covenant idea is ubiquitous in Reformed thought. ‘Covenant’ explores the key covenants in Calvinism: the covenant of redemption, which was made between the members of the Trinity (the Father, the Son, and the Holy Spirit); the covenant of works, made between God and Adam; and the covenant of grace. Central to this third covenant is God’s work of predestination—the eternal decree of God by which all human beings are appointed either to eternal life or to eternal damnation. The atonement of Christ is also considered.