Impeccable by William Swan Plumer is a pastoral work written to encourage believers unsettled by rising theological error in post-Civil War America. Plumer defends the biblical truth that Christ, as the incarnate Son of God, was not only sinless but incapable of sinning. This doctrine affirms the absolute sufficiency of Christ’s obedience and the unshakable certainty of our salvation. In a time when Christological confusion persists, Plumer’s clarity remains deeply relevant for the Church today.