There is great debate in Christian circles regarding the veracity of a letter attributed to Christ that was written either by him or a messenger. Eusebius is most famous for his ten book history of the Christian Church. A contemporary of Constantine the Great, the first Christian Roman emperor, he wrote extensively about messages exchanged between King Agbar and Jesus. In the early 20th century it was still hoped that archaeologists might find documents that proved the authenticity of this correspondence. The communications were written in a Syriac language.