The theme of the testimony of the Spirit of God is found in various Biblical writings, but it has received inadequate attention in recent theology, Biblical studies, and the philosophy of religion. This book corrects that inadequacy from an interdisciplinary perspective, including theology, Biblical studies, philosophy of religion, ethics, psychology, aesthetics, and apologetics. The book includes previously unpublished work on the topic of the testimony of the Spirit in connection with: its role in Biblical literature, an ontology of the Spirit, conscience and the voice of God, moral knowledge, religious diversity and spiritual testimony, psychology and neuroscience, community and language, art and beauty, desire and gender, apologetics, and the church and discernment. The book includes a General Introduction that identifies some key theological and philosophical topics that bear on the topic of the testimony of the Spirit, and it concludes with a bibliography on the testimony of the Spirit. The book pursues its topics in a manner accessible to a wide range of readers from various disciplines, including college students, educated non-academics, and researchers.