I have been asked to write an afterword to a collection of outstanding scholarly essays, which taken together, make up the most important volume in English which is dedicated entirely to the Contra Celsum of Origen. This is the longest work of the foremost Christian thinker before Nicaea which survives entirely in Greek; it has a claim to be either the greatest exercise in ante-Nicene apologetic or else the first experiment in a new genre. It is of all the more interest, to classicists and historians a well as to theologians, because it reproduces copious extracts from the text that it is rebutting, thus providing our most substantial specimen of pagan invective against Christianity before Constantine. The difficulties of reconstructing this work, its value as a document of late pagan religiosity, its status as a philosophical text and the identity of the Jew whom it employs as a mouthpiece are all examined in the present book by scholars more qualified to speak on these matters than I am; by contrast there is not so much (though what there is is excellent) on Origen’s response. I propose in this afterword, not indeed to undertake anything close to a full discussion of Origen’s work’s probable goals and the innovative features of the treatise, but to bring out its peculiar character, first by surveying the intellectual milieu in which both Christian apologetic and the polemic of Celsus were born, and then by showing how Origen turned his own book into a deeper meditation on the conflict between the Gospel and Greek culture. In the course of my argument I shall have occasion to comment on other contributions, never in a spirit of contention but always with the aim of amplifying rather than contradicting that which has already been well said.