I came across this sentence from Cicero in my revision of conditional sentences:
non potest iucunde vivi nisi cum virtute vivatur = it is impossible to live happily except by living virtuously.
Why is vivi (the present passive infinitive) used, and not vivere (the active infinitive)?
I can't seem to find anything in any grammar books on this. I would be grateful if someone could explain it to me.
Thank you in advance!