The devil—styled by Calvin as "God’s adversary and ours"—is ubiquitous in the witness of the New Testament. Yet contemporary Christian doctrine generally remains dumbfounded about what to do with him. At the same time, our present is marked by a resurgence in the language of the "demonic"—that is, invocation of pervasive, radical, and perhaps personified evil. In light of this perplexity, Philip G. Ziegler asks pointedly: Can the gospel actually be heard and understood without meaningful reference to this inimical entity? Ziegler presents certain motivations we might have for revisiting the concept of the diabolical as a first step toward a Reformed doctrine of the infernal. Starting with an exhumation of the origins of our religious and cultural reticence about the devil, this study ventures a new diabology grounded in the witness of the Gospels. The identity and activities of the devil are discerned concretely in their manifold contradiction of Christ as the "Way, the Truth, and the Life." The ensuing portrait of the devil yields revisionary consequences for both theology and our conception of faithful living. Through a historical sketch of received approaches to the devil in Western Christian tradition, God’s Adversary and Ours uncoils the default dogmatic architecture of diabology and reflects upon the surrounding doctrines that position, shape, and constrain its treatment. Ziegler leads us on a cautious but determined biblical-theological exploration of the identity, ontology, and agency of "that old serpent," the Enemy, whose image becomes most discernible and salient in direct contact with the person and work of the Savior. Fixing attention upon the figure of the devil in a soteriological context confronts us with what the devil does; what the devil might be trails behind. Treating diabolical temptation, demonic possession, and devilish falsehood in turn, Ziegler demonstrates what resistance to—and faithful disbelief of—these three aspects of the devil’s business might mean for the shape of a Christian life.