Celsus is a 2nd century Greek philosopher and opponent of Early Christianity.

He is known for his literary work, The True Word (Account, Doctrine or Discourse), written about by Origen.

This work, c. 177 is the earliest known comprehensive attack on Christianity.

According to Origen, Celsus was the author of an anti-Christian work titled The True Word.

This work was lost, but we have Origen's account of it in his writings.

It was during the reign of Philip the Arab that Origen received this work for rebuttal.

Origen's refutation of The True Word contained its text, interwoven with Origen's replies.

Origen's work has survived and thereby preserved Celsus' work with it.