This is an attempt to find a consistent metaphysical underpinning for Hermetic magic theory in Ars Magica 5. The aim is to come up with a system which:

  • Roughly fits in with medieval philosophy.
  • Makes sense in a setting where God the creator exists as fact.
  • Justifies the different scopes of the different Hermetic arts.
  • Is specific enough to be falsifiable.

The result is more or less a theory of Ideas00More popularly known as “Forms”. For example, all round things are related to the Idea of “roundness”, which exists independently of any individual round thing, and indeed cannot be perfectly represented in the physical world, as all real things have imperfections. To avoid confusion I’ll use “Idea” to refer to the Platonic concept, and “form” to refer to the Hermetic forms.

, with bits added on to make the magic work.

The Arts and Academe sourcebook talks about the Aristotelian theory of Ideas, which I don’t think is inconsistent with the system put forward here, as it’s mostly a way of categorising properties. Also, that book doesn’t explain how Muto and Rego fit in with the theory.

The Hermetic arts

Hermetic magic is based on several different techniques and forms, collectively known as arts. This forms a verb/noun system: the technique is the sort of effect you want to apply, and the form is the sort of thing you want to apply the effect to.

In this memo we’re most concerned with the techniques, which are:

  • Creo: creation, improvement, healing, and maturation:
    • “Creo magic makes things that exist independently into better things of their kind, which includes bringing them into existence from nothing.”
    • “Creo can both create and heal things.”
    • “Creo can make a horse as swift as the fastest horse.”
    • “Creo cannot make a horse able to run as fast as the wind, because no ordinary horse can do that.”
    • “Since maturation involves becoming a better example of your kind, Creo magic can make something mature quickly.”
  • Intellego: unhindered perception:
    • “It allows a maga to gather information directly from the forms of things.”
    • “This information does not deal with the appearances of things, unless Intellego Imaginem magic is used.”
    • “Intellego magic is not deceived by mundane disguises.”
  • Muto: unnatural transformation:
    • “A magus can grant or remove properties something cannot naturally have.”
    • “Muto magic cannot affect the properties that something has naturally, although it can add other properties to them to mask their effects.”
  • Perdo: destruction and degradation:
    • “Perdo makes things worse examples of the kind of thing they are. It is the opposite of Creo.”
    • “Perdo magic can simply destroy things, removing them completely from existence, or it can destroy aspects of a thing.”
    • “Perdo Corpus could remove a person’s weight.”
    • “Perdo Ignem could make a fire unable to burn anything.”
    • “Perdo alone can only destroy the whole of a natural property.”
    • “Perdo can only make something a worse example of what it is. You cannot sharpen a sword with Perdo, even though sharpening involves removing some of the metal.”
  • Rego: natural transformation:
    • “Rego allows a maga to change the state of a thing to some other state that the individual can naturally have.”
    • “Rego magic allows a maga to move things around.”
    • “Rego can also make a tree blossom out of season, put a person to sleep, shape a piece of stone into a statue, or weave thread into a tunic.”
    • “It cannot make an animal appear young, because mature animals cannot naturally become young.”
    • “Rego also cannot make an animal old, because aging is decay away from the form.”
    • “Rego cannot turn a brown dog black, because while dogs can naturally be black, the brown dog in question cannot naturally take on that colour.”
    • “Any change that a mundane craftsman can make can also be made by Rego magic.”

The forms are:

  • Animal: animals of all kind, cannot affect people.
  • Aquam: water and other liquids, as well as properties of liquidity.
  • Auram: air, wind, weather, and gaseous forms in general.
  • Corpus: human bodies and bodies of human-shaped magical and faerie creatures, living or dead.
  • Herbam: plant matter of all kind, living or dead.
  • Ignem: fire, heat, and light.
  • Imaginem: the processes by which things emit species11SPEH-kee-ayss. The fundamental particles of sensory data. All things emit species of different sorts constantly.

  • Mentem: minds, thoughts, and spirits.
  • Terram: solids.
  • Vim: raw magical power.

Ideas and Natures

To summarise the techniques:

  • Creo makes things into a better example of their kind: it can make a horse as fast as the fastest horse, but not faster than any horse could be.
  • Intellego tells you about the true nature of a thing, and isn’t affected by mundane disguises.
  • Muto adds or removes properties that a thing could not naturally have: it can give a horse wings.
  • Perdo makes things into a worse example of their kind: it can damage or destroy things. Perdo can also remove natural properties22Perdo is a bit of an outlier, because it seems it can do two qualitatively different things. Is there a Hermetic breakthrough awaiting discovery which splits Perdo into two arts which can be mastered individually?

  • Rego makes changes which could naturally occur: it can move things, put them to sleep, and so on.

This seems to be referencing a concept of Ideas: individuals belong to some sort of ontological groups and have “natural” properties and “unnatural” properties.

Elsewhere the core book talks about the Essential Nature of a thing. For example, a person could have “blindness” in their Essential Nature: such a person would have been born blind, and cannot have their sight restored by Creo, even though that fits under the umbrella of making things into a better example of their kind.

This suggests that either Ideas are more specific than “man” or “dog”—are more like “blind man” (and presumably “brown dog”)—or that Ideas only explain part of the story, and things have a secondary set of natural properties. I adopted the second approach (see the alternative theories section for why), and call this secondary set of natural properties the Individual Nature.

Now we can define Essential Nature:

Here is our first attempt at explaining the techniques:

  • Creo improves an object’s expression of its Essential Nature.
  • Intellego informs you about the Essential Nature of an object.
  • Muto adds new properties to an object, or removes other Muto-added properties.
  • Perdo degrades an object’s expression of its Essential Nature, or removes properties from the Essential Nature.
  • Rego changes an object in a way which doesn’t affect its Essential Nature.

This sort of works, but not fully. Where do the properties added by Muto go? To the Idea? To the Nature? How come Muto can only remove properties which were added with Muto? Why cannot Perdo remove such properties? How does an object “remember” properties removed with Muto or Perdo (so they can come back when the magic ends)? Is Intellego fooled by Muto or Perdo? The broad strokes of the theory seem right, but there are gaps.

Let’s add a new bag of properties for Muto:

To solve the problem of remembering removed properties so that they can come back, there are three options:

  1. Properties could move from the Idea into a “Shadow Idea” and from the Nature into a “Shadow Nature” and from the Quasi-nature into a “Shadow Quasi-nature”.
  2. We can introduce state: properties can be enabled or disabled.
  3. We can introduce a concept of anti-properties, which nullify an existing property.

I went for option (3). Option (1) adds three new bags of properties, which feels like a lot. Option (2) opens the possibility of things having disabled-by-default properties, which doesn’t feel right, and why would properties have a state anyway? Option (3) feels pretty contrived, but less so than (1) and doesn’t have the problem of (2).

To remove a Muto-added property from the Quasi-nature, Muto can add an overriding anti-property to the Quasi-nature. But what about Perdo? Perdo can only remove properties a thing could naturally have, so Perdo’s anti-properties cannot be put into the Quasi-nature. Consider this sequence of events:

  1. A stone weighing 10kg is found.
  2. One magus casts Muto on the stone, changing its weight to 20kg.
  3. Another magus casts Perdo on the stone, nullifying its weight.

Is the weight of the stone 20kg, 10kg, or 0kg? As Perdo can only remove natural properties, surely it cannot affect the unnatural weight produced by Muto. Therefore the stone must weigh 20kg. However, if Perdo added an “anti-weight” anti-property to the Quasi-nature, then the 20kg would be nullified, as Perdo was cast after Muto, making the stone weigh 10kg! The only way the stone could weigh 0kg is if Perdo overrode Muto, and an anti-property overrode all matching properties.

So we also need a bag of anti-properties for Perdo:

Perdo cannot override Perdo (there are no anti-anti-properties), so unlike with Muto there is no need to track the order in which spells are cast, and so an unordered collection is fine.

Both Perdo and Muto can override the Essential Nature, but Perdo cannot override Muto. So we have an unambigious way to combine the bags of properties, giving the Nature of a thing:

Now we can explain the techniques:

  • Creo improves an object’s expression of its Nature.
  • Intellego informs you about the Nature of an object.
  • Muto adds new properties to the Quasi-nature of an object, or adds anti-properties to the Quasi-nature of an object if it has the matching property already in its Quasi-nature.
  • Perdo degrades an object’s expression of its Nature, or adds anti-properties to the Anti-nature of an object if it has a matching property in its Essential Nature.
  • Rego changes an object in a way which doesn’t affect its Nature.

Alternative theories

The obvious alternative to the above theory is to unify Idea with Individual Nature: each individual has a highly-specific Idea, which encompasses both what sort of thing it is (eg, “horseness”) and also the unique traits of that individual (eg, “brownness”).

The question then becomes: how are these Ideas related?

Ideas are unrelated

Each individual has its own Idea, and there is no inherent relationship between the Ideas of different individuals. Any relationship which humans use is merely a human theory with no ontological significance.

This has two main downsides:

  1. There is no inherent reason to group individuals together in one way over any other way: if any two horse-like beings have totally unrelated Ideas, then in what sense are they both horses? All groupings become arbitrary.

    This would suggest that God didn’t create “horses”, He created many similar individuals which humans have since grouped together as “horses”. However, there clearly is some ontological significance to the group “horses”, because horses can breed with other horses, and they cannot (for example) with crocodiles.

  2. There is no justification for why you could make a spell which operates on any arbitrary horse, rather than needing to be reinvented for each individual.

Ideas form a hierarchy

The Ideas of individuals have some inherent grouping, which forms a hierarchy of Ideas.

There is an Idea of “Bob the horse”. There is an Idea of “Daisy the horse”. There is also an Idea of “horse”, which Bob’s and Daisy’s Ideas are sub-Ideas of.

The has three main downsides:

  1. It’s not clear how many levels the hierarchy should have: are there other Ideas between “horse” and “Bob the horse”? For example, are there Ideas for each breed of horse?

  2. This splits Ideas into two types: those which correspond to individuals, and those which correspond to groups. In what sense are these the same? And if they’re not the same, isn’t this just the Idea / Individual Nature split in the main theory expressed in a more complex way?

  3. What direction does the arrow of causality go? Does the Idea of “horse” have properties because all sub-Ideas have those properties; or do those sub-Ideas of “horse” have properties because the Idea of “horse” does?

What about Hermetic forms?

The theory explains the techniques, but not the forms. How do they come into it?

There are a few possibilities:

  • There’s a “hierarchy of Ideas” thing going on, where the tops of the hierarchy are the Hermetic forms. I don’t like this for the same reason I don’t like the hierarchy of Ideas: the form-Ideas seem qualitatively different to other Ideas. This also feels like it implies God came up with the forms before creating any other things, and that Hermetic forms reflect the fundamental building blocks of reality, which I’m not too satisfied with.

  • Form is another category behind Idea, making a thing’s Essential Nature the combination of the Form, Idea, and Individual Nature. But if each aspect of Hermetic magic theory requires a new bag of properties in the metaphysical theory, is the theory really explaining anything?

  • Forms are actually properties33This is essentially the difference between Platonic realism (Ideas exist independently of any particular instance) and Aristotelian realism (Ideas do not exist independently of their instances).

    , for example the form Ignem affects all things with the property “is affected by Ignem” in its Idea. However, if forms are properties, then there are no corresponding anti-properties, as you cannot Perdo away a thing’s ability to be affected by a certain form. Or maybe you can but your Perdo is immediately dispelled, as it can no longer affect the object. This feels pretty ad hoc.

I’m leaning towards the third option as it’s the least unpleasant, despite the Perdo behaviour.

Whatever the answer, one thing we can say for certain is that forms are just a crude approximation to how God built the universe.