Celsus

Celsus (; Greek: Κέλσος. Kélsos) was a 2nd-century Greek philosopher and opponent of early Christianity. He is known for his literary work, On The True Doctrine (or Discourse, Account, Word; Greek: Λόγος Ἀληθής, Logos Alēthēs), which survives exclusively in quotations from it in Contra Celsum, a refutation written in 248 by Origen of Alexandria. On The True Doctrine is the earliest known comprehensive criticism of Christianity. It was written c. 175 to 177, shortly after the death of Justin Martyr (who was possibly the first Christian apologist), and was probably a response to his work.