So are you saying that fireballs are not able to set combustibles alight by default? I don't see anything in the description that says it won't. Which leaves us in the curious position that if the player asks, "Does the fireball set the oil-drenched straw alight?" to even answer the question is making up a house rule.
You know what else you don't see in the description that it says it won't do? You don't see it saying it won't change the cloths of every baby in the D&D universe. Nor does it say it won't make me a cheese sandwich while I read this thread. So I guess it does those things by default, just the same as lighting fires.
Hesitant as I am to quote myself, the following seems pretty relevant to this:
no set of rules covers all the cases it has to when taken strictly literally, with no entailment or extrapolation permitted.
Some of the entailments are obvious and uncontentious (eg the rules tell us that recovering 1 hp takes 1 day of rest; and so we extrapolate that if my PC is 7 hp down that wil take a week of rest to recover).
Some of the entailments are more contentious. For instance, the rules tell us that alchemist's fire, burning oil and a lighted torch all do fire damage (SRD pp 66, 68), and also tell us (under the heading "Damage Types -") that "Red dragons breathe fire, and many spells conjure flames to deal fire damage" (SRD p 97). This seems to me to support extrapolation to "fire damage is the result of being burned by flames". It is pretty uncontentious that flames can set timber structures alight. Hence, I see an extrapolation to "fire damage can set timber structures alight". The extrapolations here are weaker than strict entailment, but they're much stronger than mere conjecture, or mere permissible selection from a range of feasible alternatives.
There is
no permissible extrapolation from the text around
fireballs and
fire damage to sandwich-making and clothes-changing. Whereas the extrapolation to a fireball being able to set combustible materials alight is incredibly strong, given that it does the same sort of damage (
fire damage!) as burning oil, torches and alchemist's fire, all of which have the obvious capacity to set things alight.
I don't think the notion of "by default" has any work to do here, and neither [MENTION=6801328]Elfcrusher[/MENTION] nor I has used it. The relevant notion, rather is how to describe these extrapolations from rules
which are, of necessity, incomplete in what they literally state in express words.
Here's another example: the equipment list contains jugs and pitchers (Basic PDF, p 48). But there is no entry for these items. Is it a house rule for a GM to declare that a jug can hold fluids? That a jug might spill if it is full of water and being carried by a running person, or a person walking across a balance beam?
Is it a house rule to permit a player to successfully declare "My character bangs her sword in her shield to make a noise, so as to try and attract attention?" The fact that swords banged on shields might make noise isn't called out in the rules.
None of these rulings would be a departure from
rules as written. They are all interpretations of, or applications of, the rules as they are written.
Rules as WRITTEN is what RAW means.
The rules are intended to be applied. That is what they are for. Deciding that something starts burning because within the AoE of a fireball isn't changing the rules, or adding to the rules. It's
applying the rules - in this case, the rule that (i) fireballs do fire damage, and (ii) fire damage is the sort of thing that is inflicted by lit torches, burning oil, alchemist's fire, dragon breath and spells that conjure flames.
The 'mechanics' of ZoT is that it prevents the character from speaking anything but the truth if they fail their saves. It's not a mechanical check against previous rolls, it's a check against what the character believes to be true.
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ZoT's mechanics are really a roleplaying mechanic, not a die mechanic check. ZoT places restriction on how you're allowed to roleplay within it's actions. Charm and suggestion do the same - they restrict and constrain roleplaying. Charm has no mechanical outcome the way you keep describing mechanics -- it's a roleplaying requirement, not a dice mechanic. Under your arguments, a successful charm on a PC can be ignored entirely because it doesn't have any dice mechanics and the PC can narrate however they want. Frex, 'I know I failed that save against the Evil Sorcerer's charm, but don't worry, I'm only pretending to be his friend. In truth, my patron has protected me and I will betray the Evil Sorcerer at my first good opportunity!' According to you, since Charm doesn't affect any other die rolls, I could not only narrate that but I could also betray the Evil Sorcerer at any time without violating mechanics.
ZoT is a mechanic, as is Charm Person. They are not action resolution mechanics, though - rather, they are mechanics that constrain a players' permissible action declarations for his/her PC.
As ZoT is written, it makes certain assumptions about the identify of the ingame, fictional situation and the real world, at-the-table situation. That is, it assumes that the player knows what the character knows.
It's no surprise that in circumstances where that assumption fails to hold good - which is what happens in [MENTION=6801328]Elfcrusher[/MENTION]'s Eloelle scenario - then the spell can't be resolved completely straightforwardly.
At that point we ask - what is the gameplay function of ZoT? The answer: to change the fictional situation as to which character has what knowledge; it transmits knowledge from one character to another. But which knowledge - character knowledge, or player knowledge? Normally we don't need to answer this question, because the two don't come apart; but the Eloelle scenario forces us to answer it. (Other scenarios could too - eg if the player knows more than the character.)
Elfcrusher's point, as I understand it, is that in the Eloelle scenario the player has no knowledge (because s/he is stuck with the consequences of having a 5 INT). In circumstances of player/character identity as to knowledge, ZoT would not transmit any knowledge when cast on the PC. So when the circumstances depart from that, as in the Eloelle scenario, the same should be the case. This point is reinforced by the fact that
the player doesn't actually know what it is that Eloelle supposedly knows but doesn't act on (ie the player is more ignorant than the character) and so is in no position to narrate his/her PC providing true knowledge to the NPC.
Now, though, we have to establish how is is that Eloelle - who, in the fiction, does have the knowledge - is able to avoid providing it. The obvious answer is that s/he is not affected by the spell because her patron protected her.
Eloelle's player gets no gameplay advantage from this, because all this narration does is explain, within the fiction, the already status-quo result, that the 5 INT PC has nothing to say under ZoT (this is one case where having a low INT is a benefit rather than a detriment).
If the parallel narration were applied to a charm person spell, there would be no basis for supposing that the player "could also have his/her PC betray the Evil Sorcerer at any time without violating mechanics." Such a betrayal would not be upholding the status quo. It would be changing the gameplay function of charm person, not preserving it, and would thereby grant the player a very significant gameplay advantage.
