This essay is a comparison of the teachings of Socrates and Jesus on non-retaliation and love of enemies as they appear in Crito 47c-49d and Republic I, 331e-336a, and in Matthew 5:38-48 and Luke 6:27-36. It asks in each case precisely what the authors meant and how they grounded their conclusions.
Socrates held that one must never do harm to another even in return for harm received. His arguments were based on his general theory of virtue and on certain ambiguities in Greek ethical language. Ultimately the arguments are based on a form of self-interest; retaliation is a form of injustice and hence harmful to the one who practices it. He does not propose a doctrine of general non-violence, nor does he ever say that one must actually love one's enemy.
The gospel texts go beyond simple non-retaliation and make positive love of all enemies, inside and outside the community, an absolute command of Jesus. It is a positive attitude and is not based on hope of love in return. God will reward it, but the primary motive is imitation of the Heavenly Father, whose daughters and sons the disciples are. Enemy love does not give them this status; rather it flows from the fact of discipleship.