The letter to Gratian was written in the summer of 376. Symmachus' cheerleading of the new regime (see here and here and here) had been recognized by the court, and he had been chosen for the task of reading to the senate an imperial letter which announced the execution of the hated praetorian prefect of Gaul, Maximinus.
The letter is addressed to Gratian specifically, but at times breaks into the second person plural, not only because it is conventional when there are multiple emperors to do this, but also because Gratian was the guardian of his young half-brother, Valentinian II, who had been proclaimed dubiously shortly after his father's death, and reluctantly recognized by the senior emperor, Valens, and Gratian.
To Gratian Augustus
I know that it arose through the love of which you generally judge leading men worthy, that I was employed as the reader of your sacred oration. But when I think that that speech in every way outshone whatever other rescripts that the senate has heard up to this point, I think that I too am esteemed higher than the rest; after all, for great affairs, as for great comedies, selected actors are placed on stage. In reciting plays the same honour didn’t belong to Publilius Pellio as Ambivius, nor did equal fame befall Aesop and Roscius. 2. Therefore, most excellent emperors, I embrace as offered by the divine what you planned so well for me. Your praise, lord Gratian, is my duty, since you are so spirited that when you bring healing to the republic you summon the help of my voice: for you have reduced public disorders into tranquility. It scarcely stood in your way that we all lay prone - such a great crime had the men who possessed the highest positions through wicked means unsheathed. 3. That Maximinus, savage because of his favourable fortunes, the trampler of judgments, unable to end feuds, ready to enter them, has expiated with capital punishment for everybody’s tears. Now this shines through for mankind: the senate holds its ancient rights; it is permitted to live, it is no regret to have been born, and all things look to safety; danger comes to none from poverty; the republic has restored itself to antiquity, spirits have changed from shadow into pleasant daylight, after you gave encouragement to virtue. 4. We see care taken with equal vigilance so that the corn supply is brought in to sate the city more generously, a general cleansing boils away the wickedness of money-coiners, the assessor does not tip the scales to increase the gold from the provincials, a thousand other things -- if I wished to continue about them, I’d be caught out as having consideration for your glory but none for my own incapacity. For no prudent man corrupts oracles with mere human words
5. Therefore, may your divine mind, young Augustus, the glory of the Roman name, be carried in the chariot of its own eloquence. In offering thanks we abase ourselves in humble fashion, better suited to the comic slipper than the tragic buskin, now that rhetorical flair has begun to be a possession of empire: for, as I know, you have given a hospitable place in your palace to the Muses. May this turn out well for you [both] and for your piety, since you have no memory of haughtiness or indolence, those faults of loftier fortune. When you are well, it brings adequate health to me. The good fortune besought in public prayers will ensure for your clemency that the opportunity of advancing your plans will prove as great as the pleasure in describing them. Farewell.