The Mystical Presence (1846), John Williamson Nevin's magnum opus, was an attempt to combat the sectarianism and subjectivism of nineteenth-century American religion by recovering the robust sacramental and incarnational theology of the Protestant Reformation, enriched with the categories of German idealism. In it, he makes the historical case for the spiritual real presence as the authentic Reformed doctrine of the Eucharist, and explains the theological and philosophical context that render the doctrine intelligible. The 1850 article The Doctrine of the Reformed Church on the Lord's Supper represents his response to his arch critic, Charles Hodge of Princeton Seminary, providing what is still considered a definitive historical treatment of Reformed eucharistic theology. Both texts demonstrate Nevin's immense erudition and theological creativity, contributing to our understanding not only of Reformed theology, but also of the unique milieu of nineteenth-century American religion. The present critical edition carefully preserves the original text, while providing extensive introductions, annotations, and bibliography to orient the modern reader and facilitate further scholarship. The Mercersburg Theology Study Series is an attempt to make available for the first time--in attractive, readable, and scholarly modern editions--the key writings of the nineteenth-century movement known as the Mercersburg Theology. An ambitious multi-year project, this aims to make an important contribution to the academic community and to the broader reading public, who may at last be properly introduced to this unique blend of American and European, Reformed and Catholic theology.