Few subjects make believers scratch their heads more than the doctrine of the Trinity. How can God be both one and three? How do the Father, the Son, and the Spirit relate to one another? To be sure, this biblical teaching is mysterious and difficult. Studying the doctrine of the Trinity may be hard work, but it promises great reward for followers of Christ. The doctrine of the Trinity stretches our minds, floods our hearts with joyful adoration, and moves our hands and feet to active obedience.