John Calvin (1509–1564) was an influential French theologian and pastor during the Protestant Reformation. He was a principal figure in the development of the system of Christian theology later called Calvinism. John Calvin was Martin Luther's successor as the preeminent Protestant theologian. Calvin made a powerful impact on the fundamental doctrines of Protestantism, and is widely credited as the most important figure in the second generation of the Protestant Reformation.
Aiden Wilson Tozer (1897 –1963) was an American Christian pastor, preacher, author, magazine editor, and spiritual mentor. 44 years of ministry, associated with the Christian and Missionary Alliance (C&MA), a Protestant Evangelical denomination. Among the more than 60 books that bear his name, at least two are regarded as Christian classics: The Pursuit of God and The Knowledge of the Holy. His books impress on the reader the possibility and necessity for a deeper relationship with God.
Timothy J. Keller (born 1950) is an American pastor, theologian and Christian apologist. He is best known as the founding pastor of Redeemer Presbyterian Church in New York City, New York, and the author of The New York Times bestselling books The Reason for God: Belief in an Age of Skepticism, The Prodigal God, and Prayer. Keller has been described as a "C.S. Lewis for the 21st Century", although he has disavowed comparisons to his hero.
Leonard Ravenhill (1907 – November 27, 1994) was an English Christian evangelist and author who focused on the subjects of prayer and revival. He is best known for challenging western evangelicalism (through his books and sermons) to compare itself to the early Christian Church as chronicled in the Book of Acts. His most notable book is Why Revival Tarries which has sold over a million copies worldwide. He was a close friend of pastor and writer A.W. Tozer.