Sources: Ignatius of Antioch, Letters to the Smyrnaeans 1–7, Trallians 9–10 (~107 AD); 1 John 4:2–3; 2 John 7; Irenaeus, Against Heresies 1.7.2, 3.18.5.

Docetism (from Greek dokein, to seem/appear) is the earliest and most persistent Christological heresy: the claim that Jesus only appeared to have a physical body, suffered, and died — that his humanity was phantasmal. The theological motivation is understandable: if God is infinite, perfect, and impassible, how could the divine be genuinely embodied and genuinely suffer? The docetic answer: it couldn’t — therefore it didn’t. Ignatius of Antioch (~107 AD) is our earliest anti-docetic witness, railing against those who say Jesus “suffered in appearance only” and that the Eucharist is not “the flesh of our Savior Jesus Christ which suffered for our sins.” His ferocity reflects how seriously he takes the threat. 1 John 4:2–3 gives the test: “every spirit that acknowledges that Jesus Christ has come in the flesh is from God; every spirit that does not acknowledge Jesus is not from God — this is the spirit of the antichrist.” The theological stakes: if the Incarnation is not real, the Atonement is not real — a phantom cannot truly suffer, truly die, or truly rise. Docetism’s persistence across Christian history (it recurs in every generation) reflects the genuine philosophical difficulty of holding divine transcendence and genuine human suffering together — the same difficulty that generates the Christological councils of the 4th and 5th centuries.