Zach Sherman posted in the Atrium discussion forum this apologia by St. Athenagorus. He was defending the Christians to Marcus Aurelius.
Although what I have said has raised a loud clamor, permit me here to proceed freely, since I am making my defense to emperors who are philosophers. Who of those who analyze syllogisms, resolve ambiguities, explain etymologies, or [teach] homonyms, synonyms, predicates, axioms, and what the subject is and what the predicate—who of them do not promise to make their disciples happy through these and similar disciplines? And yet who of them have so purified their own hearts as to love their enemies instead of hating them; instead of upbraiding those who first insult them (which is certainly more usual), to bless them; and to pray for those who plot against them? On the contrary, they ever persist in delving into the evil mysteries of their sophistry, ever desirous of working some harm, making skill in oratory rather than proof by deeds their business. With us, on the contrary, you will find unlettered people, tradesmen and old women, who, though unable to express in words the advantages of our teaching, demonstrate by acts the value of their principles. For they do not rehearse speeches, but evidence good deeds. When struck, they do not strike back; when robbed, they do not sue; to those who ask, they give, and they love their neighbors as themselves.
For the Christian, the goal of our instruction must always be love from a pure heart and a good conscience and a sincere faith. If we are teaching our students how to win debates while not inspiring in them a good conscience, if we are teaching them how to manipulate arguments in defense of their own beliefs rather than nourishing in them a sincere faith, if we are teaching them how to get their own ends (even for the right side) rather than cultivating in them a pure heart, and worst of all, if we are confusing them about the nature of love and in any other way setting anything other than Charity, than Christ-like love, as the goal of our instruction, then we are not giving a Christian education.
Thought itself must be an act of love or it cannot be thought with a pure heart, a good conscience, or a sincere faith, and without those manifestations of inner integrity the thought cannot help but be contorted. This cannot be brushed aside by creating a category we call academic or, perhaps even more misguided, practical, and letting those things interfere with the heart, conscience, and faith of our students.
Read it again. What is the argument for Christianity?
“Who of them have so purified their own hearts as to love their enemies?”