For Nero's first five years the empire was effectively run by the emperor's old tutor and the praetorian prefect Burrus. The tutor held that only virtue is good, and that everything else — money, health, standing, the body, the remainder of one's life — is held on loan and can be recalled without notice. He then spent two decades accumulating precisely those things at the elbow of the man doing the recalling, and that contradiction is the pressure the philosophy was written under.
Stoicism had reached Rome as a Greek import, an argument about how to live rightly that had spent two centuries in lecture halls, and the Julio-Claudians made it urgent. Under Caligula, Claudius and Nero, a senator's property, his exile and his death turned on the mood of one man, and the old question of what a person actually owns — what cannot be confiscated — stopped being an exercise and became a survival skill. Seneca answered it from the worst available vantage point: inside the palace.
He had been condemned twice before Nero was born. Caligula, offended by his success as a speaker, ordered his death and was talked out of it on the grounds that a consumptive would die soon enough anyway. In 41 CE Messalina accused him of adultery with Claudius's niece Julia Livilla; the Senate voted for execution, Claudius commuted it, and Seneca spent eight years on Corsica. Agrippina brought him back in 49 to tutor her son, a boy of eleven. Five years later the boy was emperor.
For a while it worked. After Nero poisoned his stepbrother Britannicus, Seneca addressed De Clementia to him — an argument that mercy serves a ruler's own interest, written for a reader who had just demonstrated the alternative. The essay founded a genre and restrained Nero not at all.
In 59 Nero had his mother killed, and it was Seneca who drafted the letter explaining to the Senate that she had plotted against her son and taken her own life when it was discovered. Tacitus notes who came out of it worse: Nero was past the reach of reproach, so the disgrace attached to the man who had written the thing. A year earlier the senator Suillius had attacked him in public over three hundred million sesterces amassed in four years by lending across Italy and the provinces; Cassius Dio later blamed the Boudican revolt on Seneca calling in his British loans. The reply, in De Vita Beata, is the honest one available to him: he is not a wise man, does not claim to be, and a philosopher who describes a virtue he has not reached still describes it correctly.
When Burrus died in 62, Seneca asked Nero to take back the money and let him go. Nero refused, so he withdrew without permission and stopped appearing. The hundred and twenty-four letters to Lucilius come from those last years.
The Pisonian conspiracy of 65 implicated at least forty-one people. One of them named Seneca; Tacitus records no evidence that he joined it, and Nero ordered his death anyway. He opened the veins of his arms, then of his legs and knees when an old and spare body bled too slowly, took hemlock that failed, and died in the steam of a bath, dictating to his secretaries throughout.
Almost everything after that is argument about him: Tertullian claimed him as nearly Christian; by the fourth century a forged correspondence with St Paul was circulating, and Jerome listed him among Christian authors on its strength. His tragedies handed Elizabethan revenge drama its ghosts and its five acts. Montaigne defended him, and Diderot wrote a whole book doing so. Scholars still divide over whether the essays are a hypocrite's self-exculpation or a constructed voice designed to be argued with.
The transmission is not in dispute. Chrysippus survives in fragments; much of Seneca survives entire, in Latin, which is why most readers who meet Stoicism meet it here. He wrote for the person making progress rather than for the sage — a category he was careful to say he did not belong to.