Despite the obvious abuses of these spells, is there any precedent, cannon or otherwise, for the use of mentem spells (Creo, intellego and Rego) to create the "knowledge" of a spell directly?
As in, probe the mind of a maga who has such a spell, "copy it" somehow directly to yourself? If so, wouldn't that also be possible with the arts or abilities in general?
I'm trying to find a more firm "no", such as, sorry - it is actually xp spent on your soul as much as it is in your head, but seems flimsy without the sort of awakened-avatar Mage-Revised style paradigm.
Two, off the top of my head. "Mental Construct Lab" from Covenants, and one of the spirit powers listed in the "Spirit Magic" section of Mysteries. You are in luck. Both require a "Season" or more to "fix" the knowledge, even though it has been directly "implanted". Also, look at "Memory Palaces", also from Mysteries. There are spells to affect memory listed there as well, and guidelines for that sort of thing as well, if I remember correctly.......
It should be noted that you never "learn" a spell, you (re)invent it, even if you are taught or use someone else's lab notes. At the very minimum, the sigil will be different, because each magus' magic is unique. So I would say that at most you can lift the equivalent of Lab Notes from someone's mind (Intelligo, Creo to "fix" it into your mind quickly, maybe some Rego unless he was already planning to think about it), or get him to teach him to you mind to mind (knowingly or not) with enough Rego (and some Intelligo). You still have to spend the season inventing it for yourself afterwards (but you might manage several spells in one season, as per normal rules for teaching or related laboratory abilities).
And I would say the same things for Arts and Abilities: enough Rego can turn anyone into a teacher, willing or not, and Intelligo could turn someone's mind into the equivalent of a summa, which you could memorize instantly with Creo, but you still need to spend the season learning, because knowledge is (usually) more than being able to recite a text word for word. After all, just because someone copies a text does not mean he has studied it, the rule are quite clear on that
Those, and there are other canon (one "n") parallel examples with a caveat of "...because the magic is too variable and unpredictable", or words to that effect.
If you're trying to build your credibility as an SG, we can try to track down specific citations, but if you're an SG, just be large and in charge - you're on the right track.
On the other hand there is a ritual spell that allows you to add a complete text to your memory palace. in one of my previous games one of my players had a mentem specialist who used this ritual to put casting tablets in his head, it wasn't quite as good as learning a spell but it beat trying to spont something.
Would it be plausible to use some Mentem effect to use a fellow mage as a casting tablet I wonder... That seems a little more plausible than "learning" it (which as has been pointed out, would be considered seasonal work),
If it is possible to turn a mind into a bird, I'd say that is certainly possible to turn the knowledge of a spell (part of a mind) into a physical casting tablet. Though I do not think that the Order would be swarming with volunteers...
I like it
I was however thinking more of using an InMe effect to use the targets mind as a "virtual" casting tablet...
HoH:S, p68 covers Memory. The short version is that Hermetic magic currently cannot create Inscribed Memories (learned knowledge) or Procedural Memories (physical skills), but can create Episodic Memories (event memory).
HoH:S, p70 lays out that you can turn a memory into an object and then reference that object.
The problem is that you're pulling a combination of Inscribed (knowledge of the spell) and Procedural (gestures) Memories when you yank out a spell. If the person in mind had the actual Lab Text memorized (and therefore as part of it's Episodic Memory) you can pull it and then copy.
A (Major or Hermetic) Breakthrough should allow you to do it, unless an SG rules that Inscribed and Procedural Memories are part of one's Essential Nature.
Whoa, whoa! That's a rather large leap in logic.
How does the knowledge become written language? How does that written language stay consistent with Hermetic Theory? How does that Hermetic Theory fit the (assumedly very rigid?) format of a Casting Tablet, as opposed to Lab Notes* on same?
Not that it's impossible, but it's far more easily said than done.
(* I like the Lab Note suggestion - that works on several levels for me.)