I wonder how to handle Difficult Arts if a character wants to write books about them, more specifically, I am slightly in doubt about the ability requirements. Does the character have to have an art score of 5 and is only allowed to write one tractatus for five levels of his score or is the minimum requirement a score of 2 and the maximum number of tractati hlaf the score?
I could argue for both. On the one hand the rules for writing about Arts are clear, and as Difficult Arts are treated like Arts in nearly every other respect (+3 bonus for puissant, magical defense 0 score/5) there shouldn't be an exception. On the other hand one could argue that you invest as much experience to acchieve a specific art score as you need to acchieve the same score in an ability, and so it would seem reasonable that you already know enough to write something worth reading when you reach the score of two.
Actually I lean to that second interpretation, but then I would have treated Difficult arts like abilities with respect to the effecs of the 'Puissant Art' virtue and 'Magical defenses', too. So I might be wrong again.
Of course, if the first interpretation were true, then this should mean that I could use the writing rules of abilities for accelerated abilities, too. Hm, I don't want to consider this.
I would say that by the RAW you should treat difficult arts as Arts, including the part about how to write about them. That said, I think it would make more sense to allow characters to write about them as if they were Abilities (and, conversely, to write about Accelerated Abilities as if they were Arts).
I'd note that if you make the Hermetic Arts into Difficult Arts, not changing the book-writing rules makes life much more difficult for Hermetic magi. Also, consider the scores for teaching an apprentice - if these are not changed to 2 (15 XP), teaching apprentices just became a major obstacle.
Would this be correct? If my character were to write about an accelerated ability, he would use the rules for writing about an ability?
If not, what is the (valid) counter argument?
I'm not sure either, but searches of HMRE, RM, and TC&TC all failed to turn up any answers as to how to resolve books written on Difficult Arts/Accelerated Abilities...
Looking at Hedge Magic, where it describes Difficult Arts and Accelerated Abilities, after listing the differences (how much xp is necessary to progress) is clearly states "this is the only difference between a Difficult Art and a normal Art" and "Accelerated Abilities [...] are otherwise treated as Abilities in all respects". Since none of the differences listed mention writing books, then the general rules apply, Difficult Arts are treated as Arts and Accelerated Abilities as Abilities.
If you want to change it (and I can certainly see why you would), you'll need to adopt a House Rule.
RAW is pretty clear: Other than how they advance for xp cost a difficult art is an art and an accelerated ability is an ability. You can train an accelerated ability. When you write about an accelerated ability decreasing a summae level adds 3 quality. So on and so forth.
I suggest houseruling it though. Things get crazy if Elder Sahirs for example can provide a study source of 60. Or even a more normal Sahir providing a study source of 30.
