Metaphysics for Hermetic Magic

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:

The result is more or less a theory of IdeasMore 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:

The forms are:

Ideas and Natures

To summarise the techniques:

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:

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:

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:

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.