In the discussion thread Apprentices: In my hands... about Apprentices, and in particular about patent problems in this book with grafting some new rules, how to generate apprentices in play, onto already existing rules from some 25 or so books, the book's author wrote the following (as already quoted before):
So the author explains how and why he decided to keep the specific issue of which Virtues a parens can teach to his apprentice open. He did not write rules about it to not hamper player imagination, plain and simple. He did not do so to enable 'canon experts' on the forum to use the rules omission to determine, just what is possible in the ArM5 game world.
I knew then already that such experts would not just vanish because of the author's statement, so pushed on, and got the following whipping of 'canon experts' from Timothy Ferguson - as also already quoted:
You can't have it any clearer and louder, how using Matt Ryan's omission to argue, that all Hermetic Virtues can be taught from parens to apprentice by canon, is playing fast and loose with Apprentices. That omission is explicitly meant to provide an open "basic state from which negotiation ensues", nothing more - and requires that negotiation to take place for each campaign.