I thought it might help to know where "nullius in verba" comes from, so I asked Anne Groton, a professor of classics at St. Olaf College, about it. Here's her reply.
From: "Anne H. Groton" <firstname.lastname@example.org> To: Barry Cipra <email@example.com> Subject: Re: FW: Re: [HM] Nullius in verba Date: Fri, 29 Oct 1999 06:54:28 -0500 (CDT)
The quotation from Horace comes from his first Epistle, lines 13-15 (in dactylic hexameter):
Ac ne forte roges quo me duce, quo lare tuter, nullius addictus iurare in verba magistri, quo me cumque rapit tempestas, deferor hospes.
"And lest by chance you ask by which leader, by which household god (i.e., by which school of thought) I am sheltered, I, bound to swear according to the dictates/prescribed formula (literally, 'into the words') of no (particular) master, am carried off as a guest, whithersoever the storm takes me."
The "you" is either the reader of the poem or Horace's patron Maecenas, to whom the poem is dedicated.