In this classic study, Friedrich Loofs reconstructs Nestorius's thought within the fifth-century Christological controversies. Using Greek and Syriac evidence, including the recently recovered Bazaar of Heracleides, he parses Antiochene and Alexandrian idioms, clarifies hypostasis, prosopon, and physis, and reassesses Ephesus (431) and its aftermath. The style is sober, philologically exact, and densely documented; argument proceeds by patient textual exegesis, presenting Nestorius not as a teacher of two Sons but as a conservative heir of Theodore of Mopsuestia whose positions anticipate elements later consolidated at Chalcedon. A leading Halle historian of dogma, Loofs (1858-1928) worked in the liberal Protestant tradition of Quellenforschung and genetic explanation. His Nestoriana had already collated the fragments; the new Syriac materials and his lifelong interest in doctrinal development equipped him to test inherited caricatures. Writing against confessional simplifications, he aims for a historically fair verdict without denying real tensions. Scholars of patristics, historical theology, and ecumenical dialogue will find this volume invaluable. It models critical sympathy, sharpens tools for reading conciliar texts, and invites a reconsideration of how heresy is constructed. Demanding but lucid, it rewards patient readers with lasting conceptual clarity. Quickie Classics summarizes timeless works with precision, preserving the author's voice and keeping the prose clear, fast, and readable-distilled, never diluted. Enriched Edition extras: Introduction · Synopsis · Historical Context · Brief Analysis · 4 Reflection Q&As · Editorial Footnotes.