No, and that's simply wrong, because authors write to canon. Canonically, the Aegis must penetrate, as all spells must per RAW.
Rest of stuff deleted, because it's a mental exercised designed to satisfy your need that the Aegis doesn't need to penetrate, when it has been stated elsewhere that it must, and now it appears formally in a book. It's ok to play with the Aegis not needing to penetrate, I have no issue with that, but at best it is a common house rule; it certainly isn't RAW.
Can't recall if it is in the errata, but david chart actually said that it must penetrate, and that wards need to penetrate as well. Not that a lot of us have not house ruled that (neither of those need to penetrate around here) but the official stance is that yes, they must penetrate.
Yes, author's write to canon. And the quote from Antagonists p.137 makes sense both with Aegis needing to penetrate and with Aegis not needing to. Do you have an other quote, or errata? Methinks not.
That all spells must penetrate by RAW is patently wrong.
Cheers
One Shot, just out of curiosity, how does "Sufficient" make sense if it doesn't need to penetrate. Such wording is redundant, surely?
I had previously qualified my statement regarding spells and penetration I didn't think it was necessary to do it again. I don't agree with your interpretation that it could work both ways.
In any event, I'm done. I don't like the way you state things and the way you turn the words of those who discuss things with you into pretzels to support your views. I'm satisfied that the Aegis needs to penetrate as do all spells unless there is an explicit statement in the spell or effect (Intellego spells may fit here, depending on circumstance).
Errata about that do not exist - as can be easily verified here: atlas-games.com/arm5/arm5errata.php . Could you give a quote, reference, link about David Chart's statement that you refer to?
I recall the discussions in 2005/2006 following the discovery of the ward snafu differently, as far as the Aegis was concerned - but don't have them archived.
Cheers
It is more that some authors and playtesters did not notice that wards needed to penetrate, and were happy with that. Whereas other authors and playtesters did notice and where likewise happy with that. Because everyone was happy with their interpretation, thought that their interpretation was right, and did not realise that there was an alternative interpretation, nobody initially commented on it. It was only later that it became apparent that there were two interpretations.
AFAIK, the intention when the core ArM5 book was written was always that wards (and the Aegis) need to penetrate. If it was a mistake, there would have been errata.
Huh. Interesting...
Speaking of which, another question - can formulaic and ritual spells be developed with penetration, like with enchanted items? Like, say, a Level 35 Pilum of Fire that's the same as the Level 25 version, only it also gives a bonus +10 Penetration?
Penetration for spells is a function of the casting total exceeding the level. So, I have a magus who has a CrIg CS of 61, he can get, on average a penetration of 47 on a Pilum of Fire (61+6[die]-20) and 32 on Ball of Abysmal Flame. This can be increased with the Penetration skill, and Penetration Mastery for the spell, and also if you have an Arcane Connection or any other items for a sympathetic connection. So, to get through Magic Resistance, you want lower level spells when possible.
Verditius and Bonisagus who can have high Lab Totals, higher than their Casting Totals many times, can make great use of the increases in Penetration in items.
The only difference you'd get is that a munchkin with a Casting Total of 25 vs the Spell Level 35 would get 1 Fatigue but still succeed with 10 Penetration. Abomination, I tell you! 
I have now found half an hour to search the Atlas Games Forum and look up old threads. Here's an interesting one: wards and penetration, how to make it work? .
To facilitate reading it, I reference a relevant post by John Post from its middle, which summarizes Berklist: wards and penetration, how to make it work? - #76 by John_Post . There we find
By reading the entire seven page thread, everybody can judge the discussions on the 2005/2006 ward snafu himself, and draw the conclusions for his campaign.
Cheers
The discussion wasn't about drawing conclusions, it was about RAW.
You quoted John Post, but failed to quote the next paragraph that didn't support your original position, kind proving the point I was making when I said I was done. However, I found that to be so egregious that I felt compelled to respond. John post conceded that AoH must penetrate was RAW, and then suggested it was a mistake. Mistakes or ommisions in the rules can always be "fixed" with a House Rule, but that was never my point, and until this last post, wasn't the point you were arguing against. It's the classic move of changing the argument so as not to lose it.
Here is John Post's next and last paragraph in the post.
Locnil, here you see the best and worst of Ars Magica in one go. You need to be prepared to House Rule on things as it fits the overall story. There are very few simple questions and answers, because some very basic assumptions can have some vast effects on what your saga looks like as compared to another saga, and there isn't anything wrong with that. The big thing that you should take away from this is that complex issues need troupe consensus to be resolved, rather than SG fiat. The reason being is that some simple fixes can end up nearing, or at least invalidating the concept for a magus. I've seen it happen.
That is not altogether correct, as you can see when re-reading my initial statement on this thread: Ask a simple question, (hopefully) get a simple answer - #27 by Berengar. In particular (I added two underscores):
So you see here, that I was concerned with the RAW of the rules texts of Aegis of the Hearth and HoH:S p.113, not a clarification about it by the line editor on the Berklist around 2007 - which I still do not have, and did not know of (compare for this also Ask a simple question, (hopefully) get a simple answer - #40 by Berengar ). In later posts on this thread we discussed an oblique reference in an adventure of Antagonists p.137, which I had to dig up after a passing remark here.
Not quite again, as the very text you quote shows (and in which I added another underscore):
So, if you all the time knew how the line editor explained something on the Berklist, why don't you show it in this thread. We all might learn from it. But for me "the RAW, as explained by the Line Editor," in John Post's post is a very dubious concept, unless I have that explanation. Your quoting it explicitly was already skirting the forum etiquette, as it calls on the line editor to explain himself (and do so about a mailing list discussion from around 2007). So I avoided that, without hiding the post of John Post. And just before you accuse me of hiding other posts of the 2005+ thread: you should read these all, not just John Post's good summary, to understand the subject of penetration of wards and Aegis of the Hearth.
I think that at least on this we both now agree.
Cheers
How do you handle major/minor magical focus and major/minor potent magic for theurgy?
In fluff perspective it's ok to take major focus/potent magic (theurgy), but i think this isn't very balanced option, because you can cast every non-ritual spells with bonuses.
I'm thinking of trying to run Ars myself soon online, given I'm having difficulty finding a game to play in. For anyone that has had experience doing so, what do you believe is the best online platform for running an Ars Magica game?
Are you talking about a chat/irc/real-time session where you have the players all on-line at the same time, sort of like around a global gaming table, or more like a play-by-post/play-by-email setup?
I was thinking the former. I find that people tend to bail on play by posts without warning usually.
That is vexing. I observed a lot of that in games here and elsewhere. A player disappears and everything comes to a halt. So, by and large, with Bibracte the saga I'm the ASG of here on the Atlas forum, I've designed things to that for every story a player's character is the star of the story, and others can come into and out of it as needed. Sometimes it works. Well, usually it works. The biggest issue is players trying to keep track of everything going on, and I'm working on that aspect of things, too.
I've got some friends who live nearby and are now interested/ready to do Ars. I think we're going to blend some elements of PbP and tabletop into a game. I'm involved in a game over Skype that blends activity over Skype with some PbP, too.
The other big thing, is what kind of story are you interested in telling. Certain stories do really well over PbP, and certain stories do better in other formats.
Well, I suppose ultimately it depends on the characters and players I have, as I haven't really recruited anyone yet, just planning to. Though I think I plan to run something that's fairly low on research, closer to more high fantasy adventuring I suppose. I also like to throw in aspects of the wild, unknown or bizarre into games I run. Though I suppose that doesn't narrow it down for you. I've already been considering a few possible plots...given I've bought way too many sourcebooks for someone who hasn't played yet.
I have used Google Docs to play online before, and I can probably use that or a wiki to store player information, but still trying to figure out the best way to run and advertise the game.
So, just like any other RPG, then. 
Fits with my experience as well. But I'm in no position to cast the first stone.
Anyway, got even more question. From my reread of Mystery Cults (God I love the Merinita Mysteries, even if the mainstream Merinita themselves seem a little off to me).
Does Glamour really let you physically reshape reality? You just make an illusion and it's real? It's just like the planeswalker guy from MtG - he used to be just an illusionist, but then his illusions became real. From some of the posts I read, it seems you can even use it to make bags of holding - Is this true? What about portals? If I make an illusion of a magical portal to Rome, can I then step through it and head off to the Vatican? What if I cast an illusion of healing on a wounded guy? Or an illusion of resurrection on a dead one? For that matter, must the illusions be purely physical? Can I make an illusion of someone being under my mind control, and have him obey all my commands? Or an illusion of a ghost army, then order it to attack London?
Off tangent here, but how to temporary healing spells work? Say a spell to heal all wounds on a grog for Moon duration - after the duration expires, does he get back all the wounds? Or does that fact that enough time has passed to heal them all anyway mean the wounds stay healed? What if he nearly got killed through wounds a whole bunch of times, and the healing spells on them expire all at the same time? Doe she just become heavily wounded, or does all the damage accumulate resulting in his death?
Regarding charms - so a charm that's too broad, like Mythic Europe or Person, offers no bonus. But do they still act as charms, for the purpose of the later Mysteries? Which is to stay, can a magus make a Person, Living, Mythic Europe charm, combine them into a symbol for Symbol Range, and use it as the target alongside an equally broad symbol for Symbol Target to affect everyone living in Europe?
For that matter, how are multi-aspect charms handled? I get that every additional aspect adds +3 to the Ease Factor to make the charm, but does the result count as one charm or as two (or more)? Can a charm with the aspects "magus" and "singing" be used as two charms to gain the bonus for both when used to affect a singing magus? Does it count as 2 when determining the maximum amount of charms you can use? What about for determining if you have enough charms to make a symbol? And on the other hand, can you use just one aspect, i.e. to affect a magus or someone who is singing?
For Hidden duration, what counts as a significant part? I assumed it was the majority of the target's or caster's body, but then I read a review that said it was for duplicating those stories where a wizard's spells last until someone discovers the hand that he cut off in an iron chest. So, does a small piece of the body count? How small? What if you then use magic to regrow it, does it still count as a significant part of you?
And another one - from the Realms of Power books, new magical system are introduce, Methods and Powers. How do they work when used by Hermetic magi, exactly? So the bonus is that they get to use the guidelines, but I don't really see anything regular magic can't do anyway, barring a few things like restore fatigue and transfer decrepitude. You need an appropriate Technique and Form, so you don't get anything there either. For that matter, how do you qualify? Do you just need the appropriate (Realm) Magic virtue, like Holy Magic to use the Holy Methods and Powers, and Chthonic Magic for the Infernal versions? Or do you also need the virtues themselves, like say Meditation and Wonders, before you can use the appropriate guidelines for Meditation/Wonders (thus making some of them the worst virtues ever)?
Last one: Is there any guidelines for what happens at each level of decrepitude? I know that when you get to 5 you die, but before that, are they any mechanical penalties?