I don't think that rego is appropriate. You're not moving the stone around or working it, you're transforming it in to something different. I see it as akin to changing a Walrus into a zebra being a muto spell rather than a rego one.
Would you instead use the base 2 guideline; "change dirt in to another sort of natural earth" ? That seems ok. I wrote this spell a dozen years or so ago and just copied it to this thread last summer. I'm afraid I can't give you a good explanation for why I chose the guideline I did. I mean it's not natural for a wall to turn in to a passageway, but that's probably not what I was thinking.
My best guess is that I thought that the spell altered both shape and substance so it needed a bit more than the level 2 guideline which only changed substance.
Stone naturally can be arranged into a wall or a passageway, so I thing this requires Rego. It would actually be difficult because it's a crafted item: it's Rego Crafting.
But I think that a magus can sidestep this by targeting a Wall instead of an amount of Stone (Yay, Natural Philosophy):
A Wall can't naturally be a Passageway, and therefore must be changed with Muto
I think I'll use base 2 "change dirt to another type of natural earth" to turn a Wall into a Passageway, yes.
Crafted items have been left out of the MuTe guideline (as compared to the MuHe guidelines) so I'll add +1 for complexity (shape and substance sounds like a reasonable explanation)
Guidelines referring to dirt are repeatedly used to affect crafted items in the Core spells, but that's more for manipulating them than completely transforming them...
Yea, I think the base 2 is appropriate to turn a section of wall into an archway, maybe with the added magnitude of complexity. It's like targetting a human with Muto to transform his visage. You could also Rego craft the wall into the door, as you mentioned, but more permanent than you want. You're also transforming (roughly) 15 cubic feet of stone into roughly 8 feet of stone, so Muto definitely feels appropriate; Rego would leave a pile of dust as part of it.
I mean, my online magus has Harmless magic, so my temporary doorway is an easy Perdo Terram spell. (Presented as alternate solution, if you have the right virtues and flaws)
Your argument misunderstands the phrase from ArM5 p.78 Muto (Mu) "I transform" "Muto cannot affect the properties that something has naturally". A wall can have a passageway "naturally", and a Part of a wall can be a passageway "naturally".
Of course, "naturally" can mean a lot of things not sufficiently specified in either ArM5 p.78 Muto (Mu) "I transform" or ArM5 p.78 Rego (Re) "I control". But it is a reasonable assumption, that both mean the same by it: hence making a passageway in a wall requires Rego (which clearly can reshape and rearrange stones), not Muto.
So you choose whatever 'concept' you apply "naturally" to in any way you like? Ask your troupe!
No, you wish to elaborate on the universal Form of wall among Platonic universals? Go ahead: please with quotes about whether the universal Form of wall allows windows, doors and thoroughfares or not!
For the relationship between Hermetic magic and Platonic universals see:
Reading ArM5 rulebooks assuming Platonic or Aristotelian terminology isn't helpful, no matter what your troupe decided here. But understanding especially Scholastic natural philosophy and psychology, as explained in A&A, does help a lot.
You keep saying "Ask your troupe" in a way that sounds like an insult.
Basically, I set the troupe interpretation. Any help to make that interpretation better is welcome. Dismissiveness and veiled aggressivity aren't.
The result of this theorycrafting matches the design decisions of Erik to use base 3 Muto to turn a wall into a passageway.
It might be arguable, but it isn't laughably off-base.
Thank you for the reference to A&A anyway, I'll check it out.
An object can be an example of several forms: Table, Wood, Brown... Wall, Stone, Grey...
Just inventing yourself some 'concepts' and applying guidelines to them doesn't cut it, shouldn't you think so? What am I supposed to think of that kind of argument? The best I can say about it is indeed: if your troupe is happy with it, play as you like.
On the forum I certainly can expect an argument, why these 'concepts' shall be appropriate. If you refer to Plato, this requires at least, that you show what Plato or one of his many followers wrote on that subject, and how it relates to ArM5 walls.
Did you find out what the New Aristotle and newly found works of Plato you underlined refer to? The former is a main driver in the development of Thomist and Scotist Scholastics, the latter are a base of Renaissance Humanism.
For the New Aristotle you can go straight to A&A p.9f The New Aristotle. It is a 13th century term you will find rarely in our time's summaries of Aristotle's teaching, and which refers to those central works of Aristotle becoming accessible to the world reading Latin in the first third of the 13th century.
The newly found works of Plato are TMK not explained in A&A. They refer to the problem, that of the Platonic dialogues only the Timaios was in the 13th century accessible in Latin: see here. Urbane magi reading Classical Greek (Attic) might discover Byzantine manuscripts of most of Plato in Constantinople, though: see here.
More to the point: your initial disagreement was that I wanted to apply magic to the concept of "Wall".
I quoted Wikipedia's explanation of Plato on this, but the Core rulebook already lays out the kind of things magic works on:
A Wall in an artificial thing, and for example Wall of Protecting Stone (ArM5 p153) draws from the realm of Forms the Idea of Wall rather than Stone, in order to produce a well-constructed Wall rather than a pile of rocks.
I cast my spell on the exact section of Wall that I mean to turn into a Passageway, drawing from the Idea of Passageway rather than the Idea of Stone.
There is no trace of a Wall in that section once I've cast, only a Passageway. That's the whole point of targeting a Part.
This is effectively turning something that is "Wall" into something that isn't, which is Muto.
You haven't actually argued against that, only dismissed it, which I feel entirely justified in ignoring.
As for Aristotelician Vs Platonician concepts:
The passage that you quoted was about how you could get more in-depth understanding of magic by studying the masters (adding AL to your casting and Lab scores), with different methods depending on whether Plato or Aristotle (or both, or none) was "the logical model for magic theory".
It doesn't change how Magic works in the first place, which is close enough to the concepts of both authors that a bunch of magi have been arguing about it for decades without either side getting a clear advantage.
You are arguing now! Congrats! So let's sort out at this problem, which part of Hermetic Magic Theory is Platonic and which is Aristotelian!
First, substance is basically an Aristotelian concept. Especially:
So you need to decide, whether you wish to argue following Plato or Aristotle here. ArM5 follows the latter here even with Creo. You also skipped the rest of the text you quoted, namely:
As an artificial thing by ArM5 p.77 a Wall has a complex form: a combination of several natural forms put together in a particular way.
Why is this Muto?
A Wall is not natural but artificial and hence has a composite, complex form. By turning a wall into a passageway no natural form gets changed, but only their composite. Just like Covenants p.51 ReTe 4 The Invisible Glass-Worker transforms a piece of glass into e. g. a chalice. Yes, the complex form of the chalice is different from the complex form of the piece of glass, but Muto is not needed, because
The same with the wall: it can naturally, namely by mason's work, get the form of a pathway.
So it appears, that your argument combining forms and the term "naturally" does not match ArM5 examples and rules. Maybe in this aspect Magic Theory is more Aristotelian.
Indeed: Hermetic Magic Theory takes from both Aristotle and Plato. This does not mean, that for reading a part of ArM5 you can just arbitrarily choose one over the other. You rather have to look carefully, which one is currently applied.
TMK most people who play ArM5 just do not care about Platonic or Aristotelian parts of Hermetic Magic. Playing it by the book generally works and avoids trips to the library or to the Stanford Encyclopedia of Philosophy.
You seem to find joy in dismissing others regardless of the reality of what you imply.
Knowing a lot about this game doesn't excuse your attitude.
Players just as qualified as you have agreed that Muto works.
I've already argued why I think it does, and I'm unconvinced by your arguments.
Without resorting to fundamental theory: Muto transforms, Rego rearranges. I'm transforming.
I could argue about simple and complex forms, go into symbology and different aspects of a thing having different Ideal Forms, and it could be fun.
But you're a jerk and it wouldn't.
It's a pity.
Please refrain from answering my future posts and keep your entirely hypocritical "Cheers" to yourself.
Edit: If I was an admin here, I'd add "of Tytalus" to your screen name, as a warning to others
And that is not the point. I object to your 'Platonic' argument for it.
@raccoonmasks answer makes sense: yes, one can reshape the stones in a wall, reducing their size where needed, and thereby provide a way through it - by Muto magic. MoH p.50 MuTe 10 Blunting the Iron's Bite is an example for this kind of Muto. The SG might perhaps impose Intelligence + Finesse or Intelligence + Craft: Stonemason rolls to check whether the resulting wall with the opening remains standing. But all this has nothing to do with Platonic universals.
The statement "Muto cannot affect the properties that something has naturally" keeps coming up. I'm still fairly new to this game, but there are two different ways of reading that sentence. I'll rephrase it for emphasize the difference:
"Muto cannot affect any of the properties that a particular instance of a natural object currently has."
"Muto cannot affect the platonic / essential nature of an object, nor can it change the class of objects to which that particular object belongs."
Example: You want to change the color of a rock you're holding.
Means Muto cannot do anything at all. Color is a natural property, so it couldn't be changed by Muto.
Means Muto CAN temporarily change a property of this one particular rock, but Muto cannot change the universal template or overarching class of objects called "rock" (e.g. you cannot change the platonic ideal of a rock), nor can you change the essential nature of this particular instance of a rock, so whatever changes you made would only be temporary.
Are there other interpretations of that line which I didn't think of?
So if a stone is not naturally green, turning it green can be done with MuTe or MuIm.
So Muto can be used to temporarily achieve a natural state of a blade - like being warped and blunted.
Both might be because of:
In this it differs from Creo, Perdo and Rego magic. But adding properties is powerful.
So no Hermetic magic can change something's essential nature, unless it is maintained. This includes Muto magic. Hermetic magic, including Muto magic, can change something's essential nature temporarily, though.
also limits Muto in a way: Muto needs to keep something to add properties to. Separating a target with Muto into several things would put a lot of stress on the concept of adding properties to it. E. g. arguing, that turning a boulder into a pile of building stones adds some property to the boulder, is very hard. So is arguing, that Muto can turn a piece of metal into a working armilllary sphere with all its moving parts aligned.
I think the point is that it isn't enhancing (Creo) nor diminishing (Perdo) nor naturally manipulating (Rego) nor learning about (Intellego), but changing (Muto). Make people a little stronger or a little smarter? Creo. Make people less alive? Perdo. The problem comes in when people try to abuse "change": I'll change people into a stronger or smarter version of themselves. I'll change a people into a dead version of themselves. I'll change people into healthy versions of themselves. I'll change where someone is located. I'll change how I see the world. Etc. If anything isn't the same, there is change. But that doesn't mean we want Muto to replace all of the techniques.
Can I replace "MuTe(Au)25 Short step of the ghost" (MoH92) with a spell based on "Level 5: Destroy one aspect of dirt, such as its weight or its cohesiveness." (HoH:S37)?
Might need a Rego requisite in order to not interfere with the integrity of the structure. As solidity is part of the essential nature of stone, the effect should have to be maintained or otherwise the the solidity will be restored. Correct?
Makes sense, and follows HoH:S p.38 Hauberk of Sublime Lightness.
This would then be Pe(Re)Te 25 (Base 5, +1 Touch, +1 Part, +1 affects stone, +1 Rego requisite adding an effect), right? Using Rego then begs for an Intelligence + Finesse roll imposed by the SG, to see whether the spell props up the wall adequately.
Covenants p.49 box Rego Craft Magic is not the only reason to apply Int + Finesse to Rego spells.
For a particularly troublesome and mandatory application of Finesse see ArM5 p.135 Seven-League Stride.