Psychology and theology interface at four levels: theory development, research process, data collection, and clinical operation. At each level they connect in the model of humanness (anthropology) forming and functioning there; and in that model of humanness it is in personality theory that psychology illumes theology and that psychology illumines theology. A theologian who does not take full advantage of the way psychology illumines theology is not serious about the work of theology. A psychologist who does not take full advantage of the way theology illumines psychology is not serious about the field and practice of psychology. Science, Religion, and Health explains in readable style how that interface and mutual illumination works, and why it is crucial for Christian psychotherapists and pastors.