There was an old book I read called "The Endless Line of Splendor". The theme of this book is that when justification by faith is truly understood by the people of God revival breaks out. Maybe a more God-centered way to say this would be that when revival breaks out the people of God come to a deeper understanding of justification by faith. The experience of the believer in Christ becomes focused and transfixed on the scriptural truth that we are freely accepted through the finished work of Jesus on the cross for us. Because of the forgiveness offered freely in the name of Jesus, I and all who believe, are justified or declared righteous in the sight of God. This experience Luther described as the experience of being "simultaneously saint and sinner". In one moment, we see that we are unholy in ourselves and are simultaneously perfectly loved and holy and healed in Jesus Christ. We, as our minds are opened to the truth of this one true Gospel, are both laid low and lifted up. The believer in Jesus does not know whether to sit still or to jump for joy. Truly, holiness and mercy meet at the foot of the cross as the lover of God comes to see the grace of God.
This knowledge of God makes us holy, humble and happy all at the same time.
The revivalists of history (excluding Finney) therefore were vigilant and passionate for the doctrines of Sovereign Grace. For only through a proper display of God's grace could people have "the love of God shed abroad in their hearts". It was this display of Sovereign Grace through the Gospel, where a person sees in all their being that God has called them completely unconditionally, I say that again completely unconditionally, that leads a person to have pure affections for God. Love for God is poured out in the heart of the person who by the Holy Spirit comes to know the Gospel of free justification or justification by Grace alone through faith alone through Christ alone through the foolishness of preaching. This is why Reformed doctrine or bible doctrine was so important to the revivalists of the past.
The desire of the pastoral preacher is to create, in the being, in the person of the listener, a passion for God that is stronger than the grave. The faith and practice of the Christian pastor and preacher is that Christianity is the answer to our "psychological" torment and pain. It is the knowledge of God's sovereign grace and love that brings a person into peace and joy. We are secure in the love of God like a well-parented child. This was the passion of Richard Baxter and the Puritans who were called experimental theologians in their day. By experimental, they mean theology that deals directly with the experience of the soul and the nurture of what we would call today healthy psychology. I know this sounds self-centered but it is the opposite. As preachers of Grace, we are saying the only way to be holy, humble and happy is to be God-centered. Piper explains it by saying this, "God is most glorified when we are most satisfied in Him alone". Being satisfied, like a lover on his honeymoon, is what Piper is talking about. It is this passion and love for God that is "to the glory of His marvelous grace".