Surprising nobody, most of the real problem of these definitions is spell mastery ... Adaptive Casting and Resistance.
My game rarely needs to adjuticate these, but the definition my home table uses has a few points (note my table doesn't consider CrIg +10 damage and CrIg +30 damage to be the same general base.)
Essentially Same: the spell is basically the same spell with stylistic differences. Pilum of Fire, Arrow of Flame, Sphere of Ignition. Same RDT and base.
Essentially Similar: the same Base effect and stylistically similar but different RDT. Extended Pilum of Fire, Volley of Fire, Pilum of Fire All Night Long.
Essentially Similar 2: the same stylistic effect, range duration, Target but changed base (intensity of flame, speed of movement). This would include PoF to BoAF... And DEO with a Faerie version or DEO 5 to DEO 15. Also Conjure Axe to Conjure Sword with the same base level, but not Conjure Any Weapon.
Argumentatively Similar: these are spells that can be described similarly but change Base and RDT. Pilum of Fire vs Ball of Abysmal Cold. Moon Duration Breeze vs Sun Duration Tornado. We tend to call these not similar. This includes Intelligence to +3 and Presence to +5.
Not Similar: changed the actual spell, including Form or effect. Pilum of Fire to Pilum of Chickens. Pilum of Fire to Warm Up the Chilled Grog.
Here's is what I think would be terrible with Resistance:
Player: "I have The Enigma's Gift, the same as the core spell but at Sight, the same as the core spell but at Group, and a version for 2 Warping Points at AC Range all mastered with Resistance."
SG: "None of that does any good. The one that hit you does 3 Warping Points at Sight and Group."
I still think what would really help overall, especially since I don't know where all this is headed, would be an overall consolidation of these guidelines into a single style:
Style 1: List a pile of bases rather than a formula.
CrAn: Give an animal a +X bonus to Recovery Rolls.
CrAn: Increase one of an animal’s Characteristics by one point, to no more than X higher than the average score for that kind of animal.
CrCo: Give a character a +X bonus to Recovery Rolls.
CrCo: Give a character a +X bonus to disease Recovery Rolls.
CrCo: Give a character a +X bonus to childbirth rolls.
CrCo: Increase one of a person’s physical Characteristics by one point, to no more than +X.
MuCo: Make a body resistant to damage (+X Soak).
CrIg: Create a fire doing +X damage (and an example spell outside the listed ones).
CrIg: Create a fire doing +X damage in an unnatural shape.
PeIg: Chill a person so that they take +X damage (and an example spell outside the listed ones).
ReIg: Ward against a fire doing up to +X damage.
CrMe: Increase one of a person’s mental Characteristics by one point, to no more than +X.
CrVi: Give the target X Warping Points.
CrVi: Decrease the rate of decay of an Arcane Connection as if the connection were X steps higher (subject to limits).
InFo: Sense a supernatural creature of Might X or above
Style 2: List a single base and then formula to shift it.
MuIg: Add a magnitude for each extra +5.
PeIg: Add a magnitude for each extra +5.
ReIg: Add a magnitude for each extra +5.
Style 3: Give a formula.
All those "general" guidelines.
My personal preference is a formula. Now, I know I'm much more mathematically minded than most, but it also avoids a few issues that crop up with other methods. First, with method 1 people have said anything off the list cannot happen, which is why it's a list rather than a formula; we've known for sure this is incorrect since the core book, but people have said it nonetheless. If there is a cap, such as with Characteristic improvement, it can be stated as it was in that case. Second, having a formula helps with those in-between levels which happen a lot with spontaneous magic and can be done with formulaic magic. Third, for every guideline where method 2 applies, you have to look at the guideline you're reading and the core statement together to understand it. This shows up in confusing ways even in the guidelines themselves. For example, why does HoH:S p.114 list all those ReIg guidelines for warding when we already have +5/magnitude? Meanwhile, it needs to be remembered when examining the TME p.107 guidelines for transporting fire.
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Related but separately, a question sometimes arises with Giant Blood and Dwarf with those CrCo Characteristic-improvement guidelines. Does their limit apply before or after Giant Blood and Dwarf? It's clear with CrAn that the limit is off the baseline, but not with CrCo.
I would consider a spell that has the exact same effect via corpus/mentem a similar spell to its animal equivalent.
For example, a Voice Range Momentary Individual Perdo Inflict Incapacitating Wound via Corpus and Voice Range Momentary Individual Perdo Inflict Incapacitating Wound via Animal are similar
Additionally,
Gaze of Slumber and Gaze of Slumber (but for Animals) are similar spells.
Hmm. It's a tempting example. Along similar lines, should one consider similar the creation of a rope of hemp (He), and one of silk (An); or increasing the size of a man (MuCo) ten-fold, and increasing the size of a boulder ten-fold (MuAn)?
Tempting, but tricky. Would you treat as similar all Perdo spells that completely obliterate an individual target - whether that target is a man, a boulder, a spell, an illusion, a memory, a cloud, or a woolen blanket?
As currently written, the similar spells concept does not cross Art-borders. I'm fine with this, it reduces the number of spells I'd have to check through each time.
I'd like clarification on requisites though.
Eg. A CrAq spell to create acid. Is it similar to a CrAq(Ig) spell to create hot acid?
Why not? I think it's left vague enough this example of inflicting Incapacitating Wounds would work for some troupes. Just how do the rules say that these two must not be closely related effects?
I know my own Troupe feels that PoF and BoAF are similar spells, and I am (potentially) abusing that fact for Magic Resistance Mastery.
Initially I would not have felt that way, but what the hey.
They both have the same basic effect (create fire), and both have the same RDT, however their effect is at different intensities hence different guidelines.
What about some of the rego spells, where two spells at the same RDT use the guidelines respectively "gently manipulate substance" and "violently manipulate substance" - are they similar? They use different guidelines.
But then again guidelines may as well have been phrased: "Generel: Create a fire doing level +1 magnitude damage" and therefore all fire-ball/bolt spells from the smallest to humongeous ones are similar.
The reason I don't like that PoF and BoAF are similar, is that it is too easy to get high Resistance against it.
What about direct damage PeCo spells: Those doing Light wounds are different guidelines than those doing Incapcitating ones. Although the basic effect is the same (direct damage) but they vary in intensity.
PoF and BoAF are a text-book example of similar spells. You can't get a much clearer example than that.
They have the same RDT and closely related effects. "Closely related effects include such things as doing damage with Creo Ignem" (ArM5 p101)
Thanks Erik. Then it was just me feeling I was abusing things.
By that line of reasoning, "doing direct damage with Perdo Corpus" should fall under that umbrella as well. And the School of Apromor wizard's don't get the shaft of difficult Resistance, on top of the difficulties they already have compared to School of the Founder, with their spells only affecting humanoids and ony up to a given size.
CrIg "fire" damage spells are an interesting case compared to direct damage spells, since the actual target of the spell is the fire created rather than what it damages. This goes for all Creo "attack medium" spells with the same "attack medium". Doing direct damage with something like PeCo is different since the target of the spell is what they are damaging.
This does put a restriction on the similar spells for direct damage Perdo, but even it is not as tight as you first commented. It would be doing "Direct damage to a human with Perdo". Not as broad as CrIg, but all direct damage Perdo spells against a type of target are Closely Related (and Similar if matching R/D/T) even if they do a different amount of damage. The same would apply to healing a type of target. All "Heal damage done to a human" spells are Closely Related, even if the amount healed is different. However there is a difference between healing damage and healing a disease, which are not Closely Related.
Creo attack spells with the same attack medium will be Closely Related. It does not matter if that medium is fire, ice, acid, lightning, rock, etc. If two of them have the same medium and R/D/T then they are Similar. It is important to look at the medium and not the Art. A CrAq Ice spell and a CrAq Acid spell are not Closely Related, even though they are both CrAq.
I assume you mean "Direct damage to a humanoid body, using Perdo Corpus"? I don't see it matters it the target is a human, a humanoid faerie, a magical humanoid, or a humanoid demon - they are alle affected by Corpus.
And I totally agree about the other Creo [substance] attack spells, which need to match the medium and not just the Form
Yes. The Perdo spells are limited by type of Target. I used Human since it seems to be the standard term found in most places in the AM books (including the section in AM on p.101 referenced earlier) rather than Humanoid, even if the actual valid targets are far broader than just humans.
If the "Effect" is the same general type that works on the same "Target" (and as I said earlier, Creo attack spells target the created medium), then they are Closely Related.
General type would be "Damage with Medium", "Direct damage to" "Heal damage suffered", "Change Target into something", and so on.