In first-century Rome, philosophical education was for boys from well-off families. Musonius Rufus gave two lectures against this that have survived: that women too should study philosophy, and that daughters deserve the same education as sons. His reasoning was sober and therefore hard to refute. Women received the same reason, the same inclination toward virtue, the same liability to error. Whoever wants his wife to be sensible, just and courageous must therefore teach her what he teaches his son. His opponents feared that educated women would become bold; Musonius answered that philosophy makes nobody bold, but everybody more reasonable.
A custom everyone around you considers normal turns out, on inspection, to be indefensible. Going along costs nothing; objecting makes you an oddity.
What the custom was and what people thought of it: not his. What he taught was. Musonius did not change the Rome of his day, and that was never the test. He did what fell inside his box, and two thousand years later it is still there; his opponents are forgotten.
Which taken-for-granted thing around you could you not defend on inspection? And what is the small thing you could say or do about it?
Yours, Not Yours · A Stoic practice ground · All cases