This is an example sentence in Kennedy’s Primer. It is meant to illustrate the use of certain impersonal verbs with an impersonal infinitive. I was wondering why perveniri is passive, but perhaps I have answered my own question because that is just the way Latin is. I would have written pervenire, but then again, my Latin’s not as good as Quintilian’s. I would welcome any references to other grammars.
Here you are.
Impersonal Verbs
Meagan Ayer, Allen and Greenough’s New Latin Grammar for Schools and Colleges. Carlisle, Pennsylvania: Dickinson College Commentaries, 2014. ISBN: 978-1-947822-04-7.
https://dcc.dickinson.edu/grammar/latin/impersonal-verbs
Thank you kindly. That is most helpful.