In the Neonian Baptistery, Saint Paul stands opposite Saint Peter. Paul of Tarsus was a Jew and, initially, a persecutor of Christians. While travelling from Jerusalem to Damascus, he had a vision that left him blind and led to his conversion. Unlike Peter, Paul did not meet Christ in person but encountered him through faith, and is considered the first theologian of Christianity. A symbol of the Ecclesia ex gentibus, he is the one who made Christ known to the Gentiles – those who were not part of the chosen people.
Paul is also represented according to iconographic canons born in the Roman catacombs. In the Neonian Baptistery, his face is rendered through a skilful use of delicately laid tesserae. They outline his high and balding forehead, defined in volume by small insertions of white and gold tesserae, like highlights. He has black hair and a dark, pointed beard, just as the philosophers Plato and Plotinus wore it, and his gaze is absorbed and thoughtful – a reference to his activity as an intellectual.