D&D General What is the worst piece of DM advice people give that you see commonly spread?

[Lanefan]

See some of my other examples. Skipping over the thermodynamic and/or KMT consequences of spellcasting. Accepting whatever physical weirdness must result from how you interpret HP (because there is no interpretation of HP that has no weirdness--as Gygax himself pointed out.) Dealing with the "conjured stuff is only permanent if being impermanent would be the wrong kind of hurtful." Etc. Some things are simply accepted as the new rules--even if they necessarily violate the old ones.

Some of the things you employ will, necessarily, involve the gap between what is intuitive and what is real. Because the real world, while often intuitive, is not always so. Sometimes, what makes intuitive sense to be physical theory is simply straight-up wrong.

Noether's theorem, for example, mathematically proves that, for any "differentiable symmetry" (layman's terms: for any physical property which leaves physics-in-general unchanged if you shift it, and which allows a meaningful definition of "rate of change" for all times/locations), you absolutely must have a conservation law. AKA: Because physics looks the same if you add +t seconds to things, energy must be conserved. Because motion looks the same if you shift things +m meters in an arbitrary direction, linear momentum must be conserved. And because rotation looks the same even if you spin slower or faster, angular momentum must be conserved. This isn't a proof based on empirical observation that could be disproved by finding better empirical observations--it's a mathematical physics proof. As long as the requirements are held true (the whole "differentiable symmetry" thing), these things are absolutely required by logic itself. All physical systems with consistent physical laws will conserve these things.

Demonstrably, D&D magic violates every single one of them. Portals violate both forms of momentum conservation, and nearly all of magic violates energy conservation to one degree or another. Therefore, some of physics must be violated if we are to have magic.

Unless you augment real-world physics by adding magic as another force of physics (along with gravity, weak and strong electromagnetic, etc.) and seeing where that takes you. Also, make it that magic, unlike the other physical forces, can sometimes be accessed, harnessed, and manipulated by living beings; and that those manipulations are able to temporarily cause those other forces to act in odd ways in very small* areas.

And boom - you've got a fantasy universe with solid underlying physics where magic fits right in.

* - relative to the size of the universe.

I mean, so am I, but that's neither here nor there. The fact of the matter is that snapping your fingers and causing a raging sphere of fire to appear, burn things, and then instantly disappear without consuming fuel and without combusting anything is simply, flat-out not possible. The fireball spell is simply un-physical...and that's the tip of the iceberg for magic breaking the laws of physics--by which I mean, doing things that we can prove are mathematically impossible if "the laws of physics" exist at all.

 

[Neonchameleon]

I've never been a fan of crit-fumble rules for pretty much this exact reason.

The only one I ever used is my "Doubling Down" rules, based on Dark Sun. That allows someone who rolls a nat 1 to reroll - and only if they fail the reroll do they fumble. If they don't want the reroll they have zero chance of a fumble. (One of my PCs currently loves it enough he has an ability he can reroll 1-3s).

 

[Burnside]

Hey burnside, "You should run your D&D game just like Matt Mercer, otherwise you're not doing it right"

Foiled again!

 

[EzekielRaiden]

Unless you augment real-world physics by adding magic as another force of physics (along with gravity, weak and strong electromagnetic, etc.) and seeing where that takes you.

If such forces have definable derivatives, meaning "they change in consistent and meaningful ways that can be measured" which is necessary for them to be "physical laws" as we understand the term, they must have a differentiable symmetry, and thus be subject to a conservation law. Noether's theorem is extremely difficult to evade, and doing so basically means you can't answer physics questions anymore. You pretty much literally need to have something that breaks fundamental concepts like "direction has a consistent meaning" or "numbers can't wrap around from positive to negative if they get large enough." It really, really is that much of an issue: magic, as displayed in D&D, is fundamentally not obeying conservation laws of any kind, and as a result it cannot be meaningfully described by anything we would call "physical laws."

The one, and only, way to get around Noether's theorem is to have a force with a dissipative term. But that's even less useful: dissipative forces (like "friction," which is actually a convenient fiction gathering together all the little atomic forces and such that we cannot grapple with directly) necessarily reduce available quantities over time, forbidding even the possibility of increase. Since magic needs to be able to produce more stuff (in fact, it is almost totally built around doing so!), going for a dissipative force is a non-starter from the beginning.

Also, make it that magic, unlike the other physical forces, can sometimes be accessed, harnessed, and manipulated by living beings; and that those manipulations are able to temporarily cause those other forces to act in odd ways in very small* areas.

But this contradicts physical law, which is not dependent on the willpower of living beings, indeed quite the opposite. That is one of the defining characteristics of physical law: it is simply what things do, with or without our consent.

And boom - you've got a fantasy universe with solid underlying physics where magic fits right in.

* - relative to the size of the universe.

Yes, but you have had to (intentionally) break part of real physics (forces are what they are, you can only alter them by engaging other forces, and all of these forces must either have a conservation law or a dissipative term, mathematically, if they are to make any sense at all.) That's my point. You have produced something which lets you feel like it has clean, consistent physical laws, but it doesn't. It allows for behavior that would break physics, behavior that would generate mathematical gibberish or undefinable results, equivalent to demanding a real number ("real" in math terms, as opposed to "complex") that is greater than 7 and less than 3: no such real number exists, not because we haven't dreamed of one, but because the meaning of "real number" is incompatible with "more than 7 and less than 3." Like asking for the length of the fourth side of a triangle: there is no such thing to speak about, and cannot be, if we want to talk about triangles. "Adding" such a "fourth side" to a triangle means you've stopped talking about a "triangle" anymore—just like adding a "number" that is bigger than 7 and smaller than 3 means you can't be talking about something that meets the definition of "real numbers" anymore.

By "adding" a "fourth side" to a triangle, you have broken its triangleness. By "adding" these non-conservative, mind-affectable "forces," you have broken the natural-law-ness. There's nothing wrong with that! But it necessarily means breaking part of what makes our physical universe work.

Are you familiar with the Navier-Stokes equations? The TL;DR is that they're the fluid motion equations (similar to Newton's laws, but for fluid flow.) Thing is...we don't know for sure if they actually work always. They work really really well 99.999999999999999% of the time, we've confirmed that across a host of fiendishly difficult mathematical constraints. But we do not actually have a mathematical proof that they always work, meaning, we do not have a proof that you cannot get some weird, weird set of conditions where in finite time things "blow up" or flow direction ceases to have meaning or something like that. If we did find such a condition, it would mean we would need to replace them, not that we had found new physics that allowed us to make fluids that flow infinitely fast or flow in every direction simultaneously!

 

[EzekielRaiden]

The only one I ever used is my "Doubling Down" rules, based on Dark Sun. That allows someone who rolls a nat 1 to reroll - and only if they fail the reroll do they fumble. If they don't want the reroll they have zero chance of a fumble. (One of my PCs currently loves it enough he has an ability he can reroll 1-3s).

Ah, now that's workable, because it means fumbles only occur as the result of choosing to take risk. Then it isn't "1 in 400 soldiers, on average, will cut off a limb in every battle, assuming each only makes one attack roll," which is insane. It also gives the player control over whether they take the risk or not, which is almost always a good thing in this sort of context.

 

[Lanefan]

But this contradicts physical law, which is not dependent on the willpower of living beings, indeed quite the opposite. That is one of the defining characteristics of physical law: it is simply what things do, with or without our consent.

As we know physics at the moment, yes.

But maybe we don't know everything yet.

Like asking for the length of the fourth side of a triangle: there is no such thing to speak about, and cannot be, if we want to talk about triangles. "Adding" such a "fourth side" to a triangle means you've stopped talking about a "triangle" anymore—just like adding a "number" that is bigger than 7 and smaller than 3 means you can't be talking about something that meets the definition of "real numbers" anymore.

By "adding" a "fourth side" to a triangle, you have broken its triangleness. By "adding" these non-conservative, mind-affectable "forces," you have broken the natural-law-ness. There's nothing wrong with that! But it necessarily means breaking part of what makes our physical universe work.

Or maybe it was never really a triangle to begin with, we just thought it was 'cause we can only see and-or measure three sides.

I came up with a setting-design explanation not only for this magic-as-physics-force system but for why it doesn't work here in our world, to allow for (ideally) a near-seamless integration. I can bore you with it if you really want me to, but no worries if you're not keen.

Are you familiar with the Navier-Stokes equations?

No. You're way over my head with that.

The TL;DR is that they're the fluid motion equations (similar to Newton's laws, but for fluid flow.) Thing is...we don't know for sure if they actually work always. They work really really well 99.999999999999999% of the time, we've confirmed that across a host of fiendishly difficult mathematical constraints. But we do not actually have a mathematical proof that they always work, meaning, we do not have a proof that you cannot get some weird, weird set of conditions where in finite time things "blow up" or flow direction ceases to have meaning or something like that. If we did find such a condition, it would mean we would need to replace them, not that we had found new physics that allowed us to make fluids that flow infinitely fast or flow in every direction simultaneously!

Makes sense.

That's the problem with infinity...there's always that not-quite-zero chance of something odd happening, even if we never see it and never will.

 

[clearstream]

Demonstrably, D&D magic violates every single one of them. Portals violate both forms of momentum conservation, and nearly all of magic violates energy conservation to one degree or another. Therefore, some of physics must be violated if we are to have magic.

I think of magic as symbolic and analogic, and most importantly non-scientific.

My ideal magic system would be highly chaotic... not so easy to achieve successfully in TTRPG.

 

[EzekielRaiden]

I think of magic as symbolic and analogic, and most importantly non-scientific.

My ideal magic system would be highly chaotic... not so easy to achieve successfully in TTRPG.

I mean, that was sort of my point. It cannot be reconciled with anything even remotely like "physics." Protestations that "in an infinite universe..." etc. just, frankly, miss the point. If you're going to have "physics" mean anything, "magic" as it is presented in D&D cannot exist. Something like Avatar: the Last Airbender, where magic is really limited and focused and doesn't become "do literally whatever you feel like if you practice enough and get the right training," could conceivably work--energy still comes from places and goes to places (thermodynamics remains), conservation laws can account for the change, etc. D&D magic is simply, fundamentally incompatible with Earth physics--down to its literal mathematical foundations. Derivatives don't have defined meaning in D&D land, which nixes literally all of science. This isn't a "well if you just understood it fully" kind of problem; it's a contradiction with the definition itself, and no alternative definition could recover what physics does.

Hence, I hold to my claim. What is more important is having D&D magic follow its own rules consistently, even if those rules flagrantly violate realism or similarity to reality. Once a premise or concept has been accepted and integrated--become part of the new "ground" upon which things can be built--it no longer matters whether that thing is realistic or unrealistic.

A level 20 warrior can take a dozen times the "wounds" that would slay a warhorse and keep fighting. This is blatantly unrealistic if HP are meat, and if HP are not meat, that's already unrealism right there. There is nothing physically true or real to which we can claim similarity for this; instead, it is similarity to myth and legend, to great tales and important story beats. But, because those myths and legends can feel more true than the crass demands of the physical world, we are happy to set aside, or even break, the actual rules of the physical world and instead operate by acceptable new rules. Those rules must be "real" within the fictional world--they cannot be mere arbitrary conventions or abstraction for the sake of simplicity or drama--but they do not, in any way, need to be real in our world, which is what "realism" actually refers to.

Once you've established the groundedness of something, anything goes, so long as you don't contradict that groundedness. Hence why D&D magic can do whatever it needs to, and get hand-wavy "in an infinite universe..." kinds of explanations, but having a single thing--even a very small one--that doesn't establish its groundedness is a huge, huge problem for players that value this. It's why you get arguments of the form, "If even one player in the group has <X ability that isn't grounded>, my fun will be ruined." Even though the Wizard can play sillybuggers all day with the laws of reality, the Fighter being able to use a special attack only once per combat implies groundedness no longer holds, and that one single element, no matter how irrelevant to people not playing the Fighter, casts doubt upon the whole system--if that can be ungrounded, what about all the other stuff?

 

[clearstream]

Hence, I hold to my claim. What is more important is having D&D magic follow its own rules consistently, even if those rules flagrantly violate realism or similarity to reality. Once a premise or concept has been accepted and integrated--become part of the new "ground" upon which things can be built--it no longer matters whether that thing is realistic or unrealistic.

Yes, that seems right to me, too. Another way to put it is that it establishes an imagined magical reality.

Once you've established the groundedness of something, anything goes, so long as you don't contradict that groundedness. Hence why D&D magic can do whatever it needs to, and get hand-wavy "in an infinite universe..." kinds of explanations, but having a single thing--even a very small one--that doesn't establish its groundedness is a huge, huge problem for players that value this. It's why you get arguments of the form, "If even one player in the group has <X ability that isn't grounded>, my fun will be ruined." Even though the Wizard can play sillybuggers all day with the laws of reality, the Fighter being able to use a special attack only once per combat implies groundedness no longer holds, and that one single element, no matter how irrelevant to people not playing the Fighter, casts doubt upon the whole system--if that can be ungrounded, what about all the other stuff?

I might have missed how one use of an ability per day ungrounds Fighters. Perhaps the more important point is to stress again "symbolic and analogic".

 

[Oofta]

I mean, that was sort of my point. It cannot be reconciled with anything even remotely like "physics." Protestations that "in an infinite universe..." etc. just, frankly, miss the point. If you're going to have "physics" mean anything, "magic" as it is presented in D&D cannot exist. Something like Avatar: the Last Airbender, where magic is really limited and focused and doesn't become "do literally whatever you feel like if you practice enough and get the right training," could conceivably work--energy still comes from places and goes to places (thermodynamics remains), conservation laws can account for the change, etc. D&D magic is simply, fundamentally incompatible with Earth physics--down to its literal mathematical foundations. Derivatives don't have defined meaning in D&D land, which nixes literally all of science. This isn't a "well if you just understood it fully" kind of problem; it's a contradiction with the definition itself, and no alternative definition could recover what physics does.

Hence, I hold to my claim. What is more important is having D&D magic follow its own rules consistently, even if those rules flagrantly violate realism or similarity to reality. Once a premise or concept has been accepted and integrated--become part of the new "ground" upon which things can be built--it no longer matters whether that thing is realistic or unrealistic.

That's one take. One I don't happen to agree with. Realistic just means "resembling or simulating real life". So I view D&D world as being real world + magic and supernatural. It doesn't violate the rules of physics because the actual fundamental physical reality is unknowable. We just happen to have some pretty math and theories that describe fundamental physical reality at the macro (and to a lesser degree quantum) level fairly well. We still can't reconcile the two, a handful of theories aside.

Don't confuse the ideas we have of how everything works with how everything actually works. We didn't evolve to see the world as it is, we evolved to see the world as it helps us survive.

A level 20 warrior can take a dozen times the "wounds" that would slay a warhorse and keep fighting. This is blatantly unrealistic if HP are meat, and if HP are not meat, that's already unrealism right there. There is nothing physically true or real to which we can claim similarity for this; instead, it is similarity to myth and legend, to great tales and important story beats. But, because those myths and legends can feel more true than the crass demands of the physical world, we are happy to set aside, or even break, the actual rules of the physical world and instead operate by acceptable new rules. Those rules must be "real" within the fictional world--they cannot be mere arbitrary conventions or abstraction for the sake of simplicity or drama--but they do not, in any way, need to be real in our world, which is what "realism" actually refers to.

You're conflating a couple of things. First, is the granularity of the simulation that is vastly oversimplified for a game. Yes, the rules are simple. No that doesn't mean they actually do or need to tell us every detail of what's actually going on. Next that "damage" is always a cut, abrasion or significant bodily damage. Just because your idea of what HP means doesn't match the reality of how HP work in D&D world doesn't matter. HP in D&D doesn't represent one thing, it's short term exhaustion, stresses from avoiding damage, temporarily numbness or strain. For that matter we don't know that high level fighters aren't incorporating supernatural abilities that aren't countered by anti-magic zones.

Once you've established the groundedness of something, anything goes, so long as you don't contradict that groundedness. Hence why D&D magic can do whatever it needs to, and get hand-wavy "in an infinite universe..." kinds of explanations, but having a single thing--even a very small one--that doesn't establish its groundedness is a huge, huge problem for players that value this. It's why you get arguments of the form, "If even one player in the group has <X ability that isn't grounded>, my fun will be ruined." Even though the Wizard can play sillybuggers all day with the laws of reality, the Fighter being able to use a special attack only once per combat implies groundedness no longer holds, and that one single element, no matter how irrelevant to people not playing the Fighter, casts doubt upon the whole system--if that can be ungrounded, what about all the other stuff?

I simply disagree. I could use a variation of D&D combat rules to simulate boxing. Would it be a perfect simulation? Granularity down to the level of calculating how much damage each solid blow did? No, of course not. But with the right set of assumptions of damage from a punch along with the HP of each of the fighters you could get a fairly accurate simulation of a boxing match. That's "realistic" enough for me. It would also not be all that much different from our theories of physics. We know they work based on our tests but it just lets us run vastly more granular and accurate simulations.

I'm typing this on a device I have no clue how it really works. I'm sure some people have accurate theories and calculations that describe how it works. But those are just descriptions, simulations of what is really happening. At the same time, I don't understand any of those theories or calculations and I don't need to. All I need to know is the end result. Same way with a world of magic. I don't need to know how it alters our reality, I just need to know what effect is has on D&D world reality and assume that if it's not modified by magic it works like the real world.