First, I assume you mean "Perdo," not "Personal." Second, I'm really confused by your reference to "the modern concept of entropy." Stated as simply as I can, entropy is the tendency for energy to spread out. That doesn't really do it justice, but that is the gist of it. I just don't see how Perdo closely resembles it at all.
Why do I need ReTe or CrTe to make a hole into a hole? I just make a bunch of overlapping holes, and there is a moat. I'm not saying it will be a finely detailed moat. Yes, if you want to shape it really well you should turn to other things. But PeTe can certainly cut a pretty good moat. The only way to avoid this is to say PeTe cannot make a hole.
Now let's look at the ice. I'm not saying PeIg can freeze water into a beautiful sculpture or anything like that. If you want such nice results, sure, use Rego, for example. However, we're not talking about making ice better. We're talking about using PeIg on the heat (not really, but in-game) in the water to make that heat less, resulting in cold. Cold water naturally becomes ice just like missing ground in an appropriate region around a castle becomes a moat.
You've made this comment about Ignem being too powerful before. I strongly disagree. I still consider Ignem to be about the weakest of Forms. If you want this to be accepted as part of your argument, you may want to make a thread to try to convince people this opinion has any significant objective validity.
Back to the OP to which I am in agreement on many points. Sorry to derail the thread.
I try to stick to Aristotelian Physics and make magic easier when it manipulates the world within it’s natural laws. The 4 elements being abstractions which describe behaviours and qualities of things. Each of he elements having qualities shared with other forms which can be manipulated. The element Air has the quality hot, so I hold Auram can apply hot to a thing.
Creo for accelerated movement from one state to another when it Actualizes the [form] (aging a seed to maturity), create ice, create cold to freeze, make a crumbling glacier whole again, reform/strengthen the ice on a lake
Perdo for movement away from the actualized form to degradation (aging a mature plant to death), destroy heat to make a thing cold. Destroy the ability for ice to chill. Make a block of ice crumble.
Muto for transition to something unnatural for the form: Make a thing normally cold hot or hot cold. Turn a fire into an ice cube.
Rego for an unnatural transition to a natural potential: Reshaping ice, turning water into ice.
It gets a bit complicated, but the fun is find new ways to do something. My general philosophy is if it can be reasoned, it can work, though it may not be easy for the character. I think the mental excercise and versatility encourages creativity in players. That and my troupe is a group of pedantic nerds that enjoys the argumentation in and out of character.
that's like saying you can use ReTe to start a fire because you can manipulate flint and steel to light kindling and begin building a fire. It may technically be true but it is not about an overlap in the arts. Getting the body to have a fever is a natural mechanism of the body, which is (subtly) different from simply raising the temperature of the body.
if you want hot ice you will need to raise the melting point or you would just have water.
so you asume ancient doctors were idiots who couldn't observe that people sweat when they get hot? Yes some heat does escape when you exhale, but nothing like what you have implied based on a gross misunderstanding of texts.
I would have to agree. Just because you're running a fever doesn't mean you can't get frostbite and can't die from hypothermia. It will also take time for the fever to raise the temperature of the body, as opposed to using Ignem which can do it quite quickly.
In 4th ed I played an ice maga, despite (or maybe even precisly because) ice and cold was so poorly defined.
We used reasonable (to us) interpretations and governed that ice is water in another form, Terram (despite being used in some 4th ed ice spells) is not needed for solidity. And Ignem was not needed as a requisite, unless you wanted the ice to not melt even if it was warm enough to. Surrounding someone or something with ice would chill them/it but for true cooling or freezing we'd use PeIg. And PeIg would be used to freeze water. Back them it was not clear (at least to us) that ReAq could change water from fluid to solid. If anything we thought it used Muto. But Terram was never, ever used. Sure, some PeTe or Re Te spells could destroy or move solid things, and we allowed them to work, using casting requisites. It worked fine for many years.
In 5th ed I think ice is even more clearly defined as Aquam, I have never been in doubt. And Rego is clearly (to me) used to change water into either steam or ice. I still see no need for Terram, and feel the same way about chilling people or things. And I still think PeIg could freeze water. There are more than one ways to skin a cat.
As for lava, my current saga has a magus with Elementalism using this gimmick. Our interpretation is: Magic involving lava, such as creating is with Creo Terram (lava is rock, rock can naturally be a liquid, just as water can naturally be ice), has an Ignem Requisite (no added maginitude as it's necessary). Use guidelines for damage as for Creo Ignem (i.e. at Voice Range damage is [level-5]. Resistance is versus a Terram effect not Ignem, because otherwise what is the point?Using a Creo Terrem (Ignem) spell rather than just Creo Ignem needs to have some benefit. Resistance Mastery and similar spells for Ignem spells, Pilum of Fire etc is not useful as they only cover fire not hot lava. Ward Against Heat & Flames gives a Soak bonus vs lava, because it protects against heat. Soak is modified by Ignem Form bonus because the heat of the lava is the most dangerous part. Exempli Gratia: "Pilum of Lava" CrTe(Ig) 20, Voice/Mom/Ind, dam +15.