The Apologia
Quadratus is regarded as one of the earliest Christian apologists. Only a single fragment of his Apologia survives, preserved by the historian Eusebius of Caesarea, which argues that the works of the Savior were real and enduring, instancing those who had been healed of their diseases and those who had been raised from the dead, some of whom were said to have survived to later times.
Eusebius praised the work for its intellect and its faithfulness to apostolic teaching. Some accounts identify Quadratus the apologist with Quadratus of the Seventy who served as Bishop of Athens, though sources note chronological difficulties in reconciling the two figures.