Newb question: Does Corebook contradict itself with this ex.

Very new to the game and just trying to figure out the magic system, and I have a bit of trouble with overlap of Techniques as illustrated by this example:

On page 77 of the 5th ed. Core book in the introductory paragraph to the Hermetic Arts a sentence reads: "A Muto Ignem spell transforms light, heat, or fire in some way, such as by increasing its intensity, its size, or its shape."

Doesn't this contradict the actual given descriptions of the Techniques? Muto "grants or removes properties something cannot naturally have." It "cannot affect the properties that something has naturally."
Of the three things mentioned the only one that I could see fall under Muto would be shape, if you use it to twist a fire or beam of light into a shape it could't possibly take by mundane means (such as distinctly resembling creatures or objects).

The intensity of light/fire would surely fall under Creo, right? The light that shines brighter is the better light, and the heat that burns hotter is the better fire. Only 'heat' understood separately from its source would not be intensified by Creo as heat is a property and not a substance?

The intensity of 'heat' (by itself) and the size of a fire would then fall under Rego, I think, as these are properties the things can naturally have?

Am I misunderstanding something here?

Welcome to the forum. Here's my take on the problem you pose.

Intensity, brightness and size of a fire would usually depend on what is burning. A fire Mutoed to higher intensity, brightness and/or size would not require more stuff to burn - while a fire Creoed or Regoed to do so would.

Cheers

The example with Ignem may be tricky, because a fire is directly related to the fuel it consumes.
A campfire is a specific thing (within a limited span), as opposed to the fire of a forge. The campfire burns with a specific intensity and the fire has a specific size, which is much less than the charcoal-fueled forge aided by a bellows. The campfire can't burn as intense and with as large a fire as the forge naturally - that's why you use Muto to affect the change.

A mouse can't naturally be as large as an ok, but using Muto you can affect the change.

IIRC no other Muto guidelines than Vim have restrictions as to how much size/intensity you can change without a need for Perdo/Creo

I hope this helps.
I really don't know,. I'm just thinking out loud.

Thanks for the replies both of you. That logic makes a lot of sense.

You're going to need to do these kinds of leaps of logic occasionally, because a lot of questions will arise.
And please go ahead and ask them here on the forum, you usually get good answers.

A thought adjacent, I guess, to your question - not really an answer but something tangential. Is that Hermetic magic isn't some fundamental aspect of the nature of the world, it is a thing created by people. There are lots of different magic systems in the setting and they're all different.

As such it's entirely appropriate for there to be redundancies. Ice is covered by both Aquam and Terram. There is a statement that aquam spells deal with the water nature of ice and terram spells deal with its solidity, but I'd let a magus fill up their ice bucket to chill their wine with a creo aquam or a creo terram spell. I haven't once seen that distinction come up in a way that I'd get behind it. I'd put it too you that a story guide who would quibble about it - I guess I don't want to write something unkind about them, but I personally don't see any advantage.

The question "is this spell these arts or those arts" can frequently be answered with "both" (or "neither").

Hermetic spells are defined as TechniqueForm but in fact often incorporate features from more than one Technique and/or Form. Sometimes this is made explicit through the use of requisites. I like to think that other spells also incorporate secondary Form or Technique, in amounts too small to require listed requisites and recalculation of level or casting total.

MuIg which makes a fire bigger may in fact be incorporating Creo to create more Ignem while the MuCo PRETERNATURAL GROWTH AND SHRINKING spell on page 131 of the corebook similarly effectively uses a dash of Creo or Perdo to increase or decrease the size of the target's Corpus.

All Hermetic Magi gain some knowledge (Level 0) in all Forms and Techniques when their Arts are opened, so there's no conceptual issue in allowing them to perform this mixing. The only complication is deciding when to require requisites in the defining the spell and its level. I go with a minimal approach - I'd rather define spells as MuCo than Mu(Cr)(Pe)Co.

Embrace ambiguity and rules-lawyering. Hermetics do it in-game, and it's a very scholastic/medieval thing to do.