The person and work of the Holy Spirit is perhaps the most neglected doctrine in contemporary Reformed theology, and the consequences are evident. Practical deism abounds within the church today, and our grasp of the sovereignty of God is more akin to Islamic determinism than Christian theism. Much of the teaching we hear regarding sanctification is almost completely devoid of the role of the Holy Spirit. We have relegated spiritual warfare to the realm of the fanatical and have grown largely complacent about the work of Satan and the demonic world. What’s more, our piety, our prayers, our preaching, and our evangelism and mis- sions have suffered. We are at a critical moment in our generation, and the most crucial question of our day is whether or not we will recapture a robust biblical understanding of the most neglected doctrine of our day— the person and work of the Holy Spirit.