active 180 Celsus (Platonic philosopher)

Active in the late 2nd century CE, Celsus was a Platonist philosopher remembered above all for writing The True Doctrine, a critique of Christianity. The original text does not survive on its own, but large parts of it are known because the Christian scholar Origen later wrote a detailed rebuttal, Against Celsus.

What makes Celsus interesting is the way he argued: not just as an opponent of Christianity, but as a thinker shaped by the philosophical and religious world of the Roman Empire. He drew on Platonic ideas, defended traditional religion, and challenged Christian teachings as he understood them.

Because so much about his life is uncertain, modern readers know him mostly through his ideas and through the responses he inspired. Even so, he remains an important witness to the intellectual debates of the 2nd century, when philosophy, religion, and public life were tightly intertwined.