Synesius of Cyrene (c.370-c.413) was a Neo-Platonic philosopher who became bishop of Ptolemais in the Cyrenaica. He left behind a small corpus of texts that offer much information about daily life in Late Antiquity, and about the christianization of the Roman world.
This letter, written in 406 after the siege of Cyrene, was sent to a close friend of Synesius, living in Constantinople. Pylaemenes also was the recipient of letters 61, 88, 152, 74, 100, 101, 103, 102, 129, 134, 71, 150, 151, 48, and 153.
Letter 131 is offered here in the translation by A. Fitzgerald.
Letter 131: A Recommendation
 To Pylaemenes
Know well that the definitions of geometry are infallibly true. Moreover, the other branches of knowledge are very proud when they are able, for their demonstration, to borrow something, however slight, from geometry.
 Now there is a certain principle, of course, that two things which are equal to a third thing are equal to each other. I am bound to you by the link of association, and to the wonderful Diogenes by temperament also. Both of you are friends of the one man. You must then be united to one another, even as you are united to the middle link, myself. I attach you, therefore, the one to the other by this letter, in virtue of which the celebrated Diogenes will also give himself up to your honor's friendship, and at the same time, I am sure, he will take in return my own Pylamenes.
 In calling you my own, I think I am saying nothing of which we can either of us be ashamed. Thanks to you he will have, as friends, all others who love me and also such as are useful, owing to their power. It would be doing you an injustice to doubt this. More than any one at any time he stands in need of friends to come to his assistance.
 Well, in a few words, this is his trouble. Diogenes is a loyal young man, noble and full of gentleness and courage at once, just such a man as Plato would have wished to make a guardian in his state. Further, he saw military service while still a stripling. When he had passed out of youth he was given the command of the troops in our country, and in exposing himself to dangers he incurred the obloquy of the spectators. For so do the citizens regard whatever is successful. But this man rose superior to envy. Another might have much to say on this subject, but we resemble each other too much, he and I, in our attitude towards praising and being praised, for further comment. In a word, he has conquered the enemies of his city by his feats of arms, and all evil-minded men in it by his virtue. Although stepping into power while still young, he was not ashamed of his relationship with a philosopher.
 Diogenes, such as I describe him to you, has some troublesome affairs to deal with, precisely, because he is a virtuous man, for every honest man is a gold-mine for scoundrels, and the wicked get their revenues from the other part of mankind.
 An informer is trying to extort money from Diogenes, and now, having failed in that attempt, he has brought an action against him in the courts. As he has not succeeded by this means in getting any of his ill-founded claims, for we have the law upon our side, he has turned to another plan; he is changing the civil suit into a criminal charge by trying to impute to him a misdemeanor, committed before the accused was born.
 Diogenes will not wait to be brought before justice, for we must not give way to a murderous blackmailer, nor can he abandon to this fellow the possessions he has inherited from his fathers and from his ancestors, with the appearance of disgrace in addition. Diogenes, therefore, is in want of sincere, incorruptible, able friends, like yourself, and he shall have, by the grace of God, yourself through me, and the friends who are mine and yours through you. In doing a service to Diogenes every one will acquire a claim to my personal gratitude.