"Reformed theology is not only systematic but also 'catholic,' sharing much in common with other communions that are part of historic Christianity. The sixteenth-century Reformers were not interested in creating a new religion. They were interested, not in innovation, but in renovation. They were reformers, not revolutionaries. Just as the Old Testament prophets did not repudiate the original covenant God had made with Israel, seeking instead to correct the departures from revealed faith, so the Reformers called the church back to its apostolic and biblical roots.
Though the Reformers rejected church tradition as a source of divine revelation, they did not thereby despise the entire scope of Christian tradition. John Calvin and Martin Luther frequently quoted the Church Fathers, especially Augustine. They believed the church had learned much in her history, and they wished to conserve what was true in that tradition. For example, the Reformers embraced the doctrines articulated and formulated by the great ecumenical councils of church history, including the doctrines of the Trinity and of Christ's person and work formulated at the councils of Nicea in 325 and of Chalcedon in 451."
R. C. Sproul- What is Reformed Theology, published by Baker Books, P. O. Box 6287, Grand Rapids, MI., pgs. 28-29.