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.