Seneca opens Letter 114 with a provocation. Why, he asks, do certain eras produce a degraded, mannered style of writing? His contemporaries might blame literary fashion, the influence of popular teachers, the drift of taste. Seneca's answer cuts deeper: it's about character. As the speech, so the life. When a culture's values slip toward display and away from substance, its prose goes with them.
This isn't a complaint about bad grammar. Seneca is diagnosing something more interesting: the way a person's inner condition leaks out through the sentences they build. Choppy, breathless writing that never completes a thought? That's a mind chasing novelty rather than truth. Swollen, over-decorated prose? A man hiding behind ornament because he doesn't trust what's underneath. He writes to Lucilius about the fashionable style of their own day — short staccato epigrams, glittering surfaces, sentences that wanted to be admired at every turn rather than to say anything durable.
"As each person lives, so does he speak."
His favorite example is Maecenas, Augustus's great literary patron and one of the most powerful men in Rome — a man Seneca clearly likes as a human being. But Maecenas's prose was notorious: twisted syntax, staggering metaphors, sentences that seemed to have been written while drunk on their own cleverness. Seneca quotes him not unkindly but relentlessly, line after embarrassing line. The portrait that emerges isn't of a bad writer but of a man who wore robes to avoid looking at himself. Maecenas was famously soft in his habits — ostentatiously unsoldierly, given to luxury — and his style matched. The prose is the man.
What Seneca wants from writing, and from a person, is the same thing: integrity in the original sense, the quality of being undivided. A sentence that means what it says. A life that is what it appears. He comes back to this from different angles throughout the letters — in Letter 40, he argues against rapid-fire speech, the person who rushes breathlessly through an argument having nothing to say and hoping you won't notice. In Letter 75, he tells Lucilius that a letter should read the way a friend talks at close range, without performance. And in Letter 59, he worries about hollow words, the way language can be deployed to simulate feeling rather than carry it. Form is never merely form.
Susan Sontag spent her intellectual life testing this claim from both sides. Her early essays — collected in Against Interpretation (1966) — are deliberately flashy, combative, designed to provoke. She later described that style as a kind of armor, a way of being impressive before anyone could be disappointed. As she got older, and especially after her first cancer diagnosis, the prose changed. Illness as Metaphor (1978) is spare and exact; the later journals, published posthumously as Reborn and As Consciousness Is Harnessed to Flesh, show a writer stripping ornament away as the stakes rose. The style tracked the person, decade by decade — which is exactly what Seneca would have predicted.
You don't need anyone's biography. Read a page of their prose with care and you'll know something true about them — more, perhaps, than they meant to show.