Entertaining the notion of eliminating Magic Theory....
What defines a Bonisagus magus, then? I like my Bonisagus with a monster MT, who can invent spell he can't cast reliably. He is interesting.
Thanks for reminding me of the details. This definitely fits with my contention that the book rules are the single biggest reason for power escalation in the game. Down with the tractatus!
Agreed. Or simply reduce tractatus to a quality of 1 to 5. No need to supress them, but vastly reduing their XP output.
I still like the 3rd edition study rules, though. With limits, since I had a magus spend 4 years learning nothing in those rules.
Or just limit the supply of books? 
Seriously.
People complain about the power creep of Ars Magica, but often times fail to realize that their choices (and perhaps assumptions) are the leading cause of power creep.
Q10+ Tractatus too common? Need to examine how many magi are in the order, capable of writing such a book. How many have they already written? How much do they get in income from the volume? Spending some time designing a few covenants, from the Covenants book I've determined that books and vis stocks are ridiculously cheap and it colors our perceptions on what is possible. I think there are probably too many tractatus floating around in people's sagas, and they are relatively easy to come by.
Books, within the mythic paradigm are just too common. I don't mind there being a variety of books, but, IMO, there should be very few copies. And you should have to go somewhere to get access to them (not just Durenmar). Guy writes a Q12 Tractatus on some Art or Arcane Ability, he's not going to make copies for distribution, he's going to host magi at his covenant, and charge them for the privilege of reading his book. Only when the revenue stream from that falls off precipitously will he even entertain making copies of the book for sale. Make it so that there isn't an exchange of books, or it's very uncommon. Enforce travel and pilgrimages for knowledge and you'll end up with a vastly different game. If it takes a season to get somewhere to read that important tractatus, then it probably takes a season to get back. ReCo teleportation can change this time, drastically, but again, if the quantity of tractatus are limited, then it's not a huge consideration.
I'm beginning to think that there is a foundational set of books out there that pretty much every covenant has, and they're all the same, all copies of an original source work. And then there are a few special books out there that are guarded like treasure. The Q15L15 Summa that only cost 30 bps to buy (where that would only b 3 tractatus), for example. Why does the Q21L6 book exist? I think when designing covenant libraries, more thought needs to be given to the underlying implications that has on the entire world, and not just the covenant.
Changing the mechanics of Ars is a lot harder than changing some of the assumptions we base our sagas on. I would recalibrate those assumptions and choices, first, before trying to manhandle the overall system.
Certainly, but I would point out that the assumption of unlimited high quality books comes from Covenants and so can reasonably be considered to be "official" by players. I for one was astounded by the level and availability of books suggested within that publication compared to the core book. Perhaps this was just my misunderstanding of the core. Given the official nature of Covenants, it seems that subsequent works follow that same model. So in a way it is part of the "rules" (broadly considered).
Covenants provides only a rough guide of how to price things; it does nothing about setting the expectations for what the world is like[1]. It may very well be that it is possible to buy a Q15L15 summa, or dozens of Q10 or Q11 tractatus. On the same side, that could also be possible because the underlying world has multiple copies of these exact texts, and few other books beyond them. Books are precious in the Mythic Paradigm. It's easy, with covenants boiling it down to an arithmetic exercise to forget that the world still needs to be designed and have some consistency. People build the covenant, forget about the world, and when they need something, they assume that they can get it elsewhere, because other covenants were built like ours, right? Well, if they were, then they have many of the same books.
Just because it is part of the rules doesn't mean you can't consider the implications of what those rules do to the world. Look at the implicit assumption I outlined above: my covenant has X, so other covenants have A through H, and we can trade. That shouldn't be the case, especially if XPs and books are a runaway problem in the saga.
[1] Although, I can see, and have felt it's very easy to fall into certain expectations about how the world might work from those guidelines.
I'm not sure it would still be Ars Magica then.
Inventive Genius.
Most people who live within a world attempt to use the way things work to their advantage. Nowadays we have entire professions of people who do that in a formal or semi-formal way, yet people have been doing this for as long as there have been people.
That is to say, people within a world try to optimize.
I'm pretty sure that in what I said, that it was taking it as implicit. Even if you change the rules, and try and recalibrate, people will still continue to optimize. Unless you examine and make certain assumptions explicit within the saga cosmology, you're taking it as implicit that any book does exist, simply because it is possible to mechanically make it exist.
Threre is a lot of effort being spent to recalibrate and move away from a "powerful" setting, when it is the nature of Ars Magica to have powerful magi and it is well within the ability of the SG and the troupe to create a setting that limits their power without trying to redesign the mechanics from the ground up.
I'm not taking that as implicit at all. But I am taking it as implicit is that if it is easy and beneficial to produce a book, there is a high probability that the book will be produced, and that people will organize themselves and create social structures toward that end if doing so is very beneficial. Of course, other people might try to stop that process if doing so is highly beneficial to them.
I read what you wrote and for me that boils down to "Yes, mechanically it makes sense, but since the game mechanics don't model the kind of game we want to see, let's encourage any SG to screw any character who tries to leverage those mechanics--and call it storytelling." (FWIW, that kind of game does often work well, since it generates plot.)
But that's just me. I don't really mind the higher power levels. I like it when mechanics and world mirror each other.
Anyway,
Ken
Then design the magus who writes that Q15L15 summa. What does he look like? Same with the Q11 Tractatus...what does he look like. And then why is he allowing it to be sold willy-nilly throughout the Order, instead of making people come see him at his Covenant and pay for the privilege of reading his magnum opus?
Covenant's provides an abstraction for equipping a covenant with resources. I agree that maybe they could have done better, but I don't think it's as bad as people thing if they just stop and look at what's possible and separate it from what's probable or reasonable.
Covenants makes the problem worse with its (to me) absurdly high quality levels but the problem is tractatuses themselves. I much prefer the early AM model (and the current Summa model) which limits the ability levels that books can pass on based on the knowledge of the author. It's just silly to assume anyone, regardless of Art level, can write a book that an archmage benefits from.
Call me cynical, but I'm pretty sure that the author of the original tractatus rules was in grad school at the time, with perhaps an exaggerated opinion of what a student can add to the body of knowledge...
So, death to tractatuses!
technically, I believe that would be death to tractatus (possibly tractatuus), but never mind that.
I didn't say anything about L15; one only needs L10 to achieve YR7's issues. But.... Com 3 and Good Writer (whatever it's called) gives us q12 I think. Calf and Cow supported by elder magi eager for the next tractatus and Redcaps eager to have more valuable mail to distribute keeps pesky guests away from the covenant. It doesn't even have to be the writer who organizes this. If only there were a well-organized House run by elder magi with resources to commission awesome texts for themselves and their House, read them first and sell them to their friends in the Order for low, low prices and future goodwill... oh wait, I don't even have to make these guys up.
The plural of tractatus is...wait for it...tractatus. 
Students can add a great deal to a body of knowledge, sometimes it provides inspiration. Sometimes it is on an aspect of the subject that the author has previously ignored or discounted, but now needs to understand better. When I taught I learned stuff all the time, granted I didn't teach very long...but I learned.
If you want to get rid of Tractatus, though, it's pretty simple to do so.
Disregard the level, then. Com 3 and Good Teacher. How many of them are in the order? Again, you're making some assumptions, and you can choose otherwise. Very easily, and in fact, probably should. Maybe Redcaps only deliver mail, and haven't learned spells to shrink books down to a size that they can be transported easily? I think our assumptions towards books color the perceptions of the characters. Books are probably rarely copied for distribution. Further, the book can be much more useful when used as a means of bringing visitors to the amazing writer's covenant... And then there's the question of how did his Arts get so good that he could write that L15 or even L10 book? If books weren't the way it happened, then he's going to make sure that he can recoup as many funds as possible...
Those are saga dependent questions, and are easily divorced from the mechanics. Ars is a game where I like to say, sure, you can do anything, but why are you doing that. Asking the why, and then backing that up all the way through can lead to starkly different conclusions. Just because you can make a book by the broad and generous guidelines presented in Covenants for use at the PC covenant doesn't mean one necessarily should, or that the SG and/or troupe as a whole decide to veto the book.
I take things from the perspective that if the PCs can optimize this sort of thing, so can NPCs. The rules for vis study make it prohibitive; the rules for book study make it attractive. So if I were one of the magi running House Tremere or House Guernicus, which would I want to support, especially since I will be one of the first to benefit? If Redcaps don't have a spell to shrink a book, why wouldn't an elder Tremere, Guernicus, Mercere or other interesting party simply spend a season creating this spell? The Tremere could have a filius do the work for him for the good of the House and Order.
I'd rather have more tractatuseses out there because as an elder magus, the more books that exist the more I get to read. This is more important than having entourages tracking mud (and inconvenient stories) into my covenant.
Your question about "why" comes from the perspective of a player wanting to guide a saga in a certain direction. My "why" comes from the perspective of someone in that saga trying to do his thing as best as he can. A magus can cultivate good writers by finding likely apprentices, by making life good for the few magi who have these virtues and even by encouraging cults that initiate appropriate virtues. Heck, good communication is just a few CrMe spells away: A magus can become the change he wants to see in the Order. Or help someone else along. This is much cheaper than studying from vis.
How many times do PCs get the complete opportunity to optimize everything that they want. As an SG, I throw up roadblocks into PC plans all the time. NPCs have the same stuff happen.
When I ask why, I ask as the SG, about what existed before, and what is reasonable. Not all mystery cults exist. Those rituals that increase characteristics aren't easy to acquire and/or have someone to cast them. Yes, they can be invented from first principles, certainly. Or they can be purchased, maybe, at great expense of Magical Merceres. And they have a huge risk, if the caster is not a Mercurian, and/or doesn't have it mastered for multiple mastery ability levels. Remember what I've said before. Enforcing rituals such that they are always stressful is going to make botching much more common. It's going to make the desire to cast to spells much intense and/or more expensive.
Those CreMe 60-65 rituals...costing 12-13 pawns of vis, and requiring lab totals in the 70s to invent in a somewhat reasonable period of time...there's a huge investment of time there. And why does my magus care beyond training the apprentice he has now and then kicking him out the door? As much as there are genial master/apprentice relationships, so to are there the adversarial ones.
It comes down to the troupe deciding the world they want to live in and then making certain decisions that create it, and then play in that world. Covenants can provide enough room to create both, and it is the responsibility of the troupe to flesh it out. With great power comes great responsibility.