the early bishop Clement (1 Clement), and a letter by the bishop Polycarp. Three other texts are preserved in the form of a letter, though scholars question whether these writings were ever really intended to function as such: 2 Clement, which is probably an ancient homily or short sermon that has been attributed by tradition to Clement of Rome; the Letter of Barnabas, which is a sermon or theological tract by an unknown author; and the Letter to Diognetus, an early apology, or defense of the Christian