Celsus of Ephesus was a prominent Greek philosopher and writer who lived in the 2nd century CE. He is best known for his work, the "True Doctrine," which critiqued early Christianity and defended pagan beliefs. His writings provide valuable insights into the religious and philosophical debates of his time. Celsus's arguments were significant in the context of the growing influence of Christianity, as he sought to challenge its teachings. His critiques were later addressed by early Christian apologists, including Origen, who aimed to refute Celsus's claims and defend the faith against such philosophical opposition.