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In multiple questions that deal with how the rules lead to outcomes that differ from what one would expect from real-world physics, answers make the point that "D&D is not a physics simulation/simulator", that instead it is a game that has rules optimized for a fun and engaging gameplay experience (I am convinced, correctly).

How does one justify this response to problems as it is often presented without justification, and what support for this claim is present in the actual rules? The main sections I can find are from the DMG, on page 4 and 5:

The D&D rules help you and the other players have a good time, but the rules aren't in charge. (...) The last part helps you adjudicate the rules of the game and modify them to suit the style of your campaign.

The rules don't account for every possible situation that might arise during a typical D&D session

From Tasha's Cauldron of Everything, page 5

You don't need to know every rule to enjoy D&D, and each group has its own style -different ways it likes to tell stories and to use the rules. Embrace what your group enjoys most. In short, follow your bliss

makes the point that joint story-telling is more important than rules adherence. And from Xanathar's Guide to everything (and the Sage Advise companion):

Rules are part of what makes D&D a game, rather than just improvised storytelling. The game's rules are meant to help organize, and even inspire, the action of a D&D campaign. The rules are a tool, and we want our tools to be as effective as possible

(bold added). In particular the last one could be interpreted to support this claim, as it states the objective of the rules is action, and that the rules need to be effective for this, which more realistic and complicated rules would not be.

Are there statements in published materials that more directly say that the rules are a simplifying abstraction, and are on purpose not aiming at realistic simulation?

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  • \$\begingroup\$ Comments are not for extended discussion; this conversation has been moved to chat. \$\endgroup\$
    – Someone_Evil
    Mar 16 at 20:13
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    \$\begingroup\$ It feels to me like you're asking to prove a negative. Rather than a a citiation that D&D is not a physics simulation, it seems more the case that there is not a citation that it is a physics simulation. \$\endgroup\$
    – Flater
    Mar 18 at 13:30
  • \$\begingroup\$ You could contrast D&D with other tabletop RPGs which do explicitly attempt to model reality (GURPS, for example). \$\endgroup\$
    – Marq
    May 11 at 13:25

3 Answers 3

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In the AD&D 1st edition Dungeon Masters Guide p.9, Gary Gygax writes:

Of the two approaches to hobby games today, one is best defined as the realism-simulation school and the other as the game school. AD&D is assuredly an adherent of the latter school. It does not stress any realism (in the author's opinion an absurd effort at best considering the topic!). It does little to attempt to simulate anything either. ADVANCED DUNGEONS & DRAGONS is first and foremost a game for the fun and enjoyment of those who seek to use imagination and creativity.

The D&D 3.5 Rules Compendium contains an essay by Andy Collins titled "Abstract or Simulation":

Every edition of D&D has struggled to find the right balance between simulation and abstraction that achieves maximum playability and fun. Overall, the game leans more heavily toward abstraction, and that's not an accident.

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    \$\begingroup\$ upvotes with bewilderment because of course Quadratic Wizard has an historical citation for this \$\endgroup\$ Mar 16 at 16:36
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    \$\begingroup\$ Great citation, putting vast knowledge to use: however, the dnd-5e tag implies that OP wants 5e specific answers, does it not? \$\endgroup\$ Mar 16 at 18:06
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    \$\begingroup\$ @TheDragonOfFlame Tags describe the content of the question, but can't do additional things like place down rules for answers. The corrolary tho is that in asking about D&D 5e, we expect answers be relevant to that question, and we use our judgement to determine what that threshold is. We can trivially judge that a mechanical answer sourced from AD&D 2e does not answer a mechanical question about D&D 4e. In this case, we can judge that an answer citing multiple previous editions can indeed be very relevant to explaining what's true for the game in general and continues to be true for D&D 5e. \$\endgroup\$ Mar 16 at 23:40
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    \$\begingroup\$ It may be helpful to note the context of Gygax's 1E quote. This was a few years after Arneson's rules in the OD&D Blackmoor supplement that included hit locations, hit points by body part, attacker height differential adjustments, etc., which slowed down the game greatly and were ultimately discarded. So arguably this was a response to his partner's going overboard on certain issues... \$\endgroup\$ Mar 17 at 1:20
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    \$\begingroup\$ ... The 1E DMG passage you quote continues with this: "This is not to say that where it does not interfere with the flow of the game that the highest degree of realism hasn't been attempted, but neither is a serious approach to play discouraged." Arguably any game is a model/simulation of something from "realism", the question is just where the level of abstraction is set. I've blogged about that here. \$\endgroup\$ Mar 17 at 1:22
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"D&D is not a physics simulator" is shorthand for a more thoughtful thesis.

As you have observed, "D&D is not a physics simulator" is an oft repeated response to people who seem to bring expectations about the behavior of real-world physics to the table of play. At face value, the saying really is not true, but no one intends this phrase to be taken at face value, it is just shorthand for something more meaningful.

Obviously, D&D does make some attempt to simulate physics. In real life, things fall down due to gravity. If D&D were not making some attempt to simulate this, we would not have rules for flying, falling, and fall damage, but of course, we do. The rules for falling and fall damage are simulating the real world phenomenon of gravity. So what do we really mean when we say this?

The rules of D&D often fall short of meeting our expectations about real world physics.

When we approach the game armed with an expectation that the rules will produce consistency with Newtonian Mechanics, that expectation will not be met because Newton's Laws of Motion are not part of the rules of the game. We're here to play D&D, not crunch numbers using Newton's kinematic equations, so the rules for falling are far more simple than \$\Delta x=v_0t+\frac{1}{2}at^2\$:

When you fall from a great height, you instantly descend up to 500 feet.

Now, the closest thing to a proper reference for this idea found in the game rules comes from the introduction to the Dungeon Master's Guide:

The rules don’t account for every possible situation that might arise during a typical D&D session. For example, a player might want his or her character to hurl a brazier full of hot coals into a monster’s face. How you determine the outcome of this action is up to you.

There is a physics problem and a medical problem associated with hurling burning coals at a person, and one could theoretically try to simulate the resulting injuries reliably if they were armed with sufficient knowledge and experience. But the rules of the game don't try to do that. The rules admit that they cannot account for everything and instruct the DM to make a ruling and move on. It is a natural corollary of this quote from the DMG that the rules will fail to meet your expectations about real world physics. And that is what people mean when they say "D&D is not a physics simulator".

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    \$\begingroup\$ The fall damage rules are a great example of 5e starting with correct physics and then simplifying. Impact energy is a rough proxy for damage. Gravitational potential energy scales linearly with height, and thus kinetic energy at impact, except for terminal velocity if you fall for long enough. 5e fall damage is linear with height and then just capped, instead of gradually approaching a max. Obviously sensible choice. But gravitational potential (and kinetic) energy scale with mass as well, and 5e completely ignores that. A mouse can walk away, a human is broken, a horse splashes. \$\endgroup\$ Mar 17 at 0:04
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    \$\begingroup\$ @PeterCordes technically that is a relation of mass to drag, not absolute mass. A human with a parachute (slightly more mass!) is suddenly is a lot healthier. \$\endgroup\$ Mar 17 at 0:32
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    \$\begingroup\$ @fyrepenguin: Right, mass assuming constant density and shape, because of cube vs. square scaling of mass vs. cross-sectional area. Which is close enough for earthly animals, but as you say not when they're wearing light-weight high-area stuff. Like a large spider with a line of silk to catch the wind. \$\endgroup\$ Mar 17 at 0:40
  • \$\begingroup\$ Let us continue this discussion in chat. \$\endgroup\$ Mar 17 at 3:11
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The phrase predates 5e

As Quadratic wizard shows, the sentiment that D&D was not meant to be simulationist was part of the rules very early on. I don't think there is anything approaching the directness of "D&D is not a physics simulation" in the 1e rules, though.

The phrase 'physics simulation / simulator / engine' itself is at least as old as third edition. Just on this site we have questions and answers saying things like:

"Fourth edition was not designed as a physics simulator." (May 2013 answer to a question tagged 4e)

"D&D is not a physics engine," (March 2014 answer to a question tagged 3.5e)

These were the oldest examples I could find of the exact phrase for each edition - but there are dozens of more examples both later and if you allow for the general idea rather than the exact words. It is clear that the idea or spirit that this saying expresses was already a common part of the gaming culture long before the fifth edition rules were written.

Not in 5e published materials

Thomas Markov shows what may come the closest in 5e rules - 'the rules are not meant to cover everything'. A similar declaration of spirit is to be found in a 2020 tweet from Jeremy Crawford:

In D&D, everyday things—walls, gravity, bread, laughter—work the way we expect them to, except for when the rules say otherwise.
For example, D&D has magical effects that pass through walls, for walls are assumed to be impenetrable, unless you damage the wall itself. (Apr 2020)

Specifically referencing gravity, Crawford here says that we can expect it to work the way it does in our world, except when the rules say that it doesn't. In other words, sometimes the rules of D&D do not follow the rules of physics, and we should not expect that they do.

But these are a few steps short of what you are looking for - 'the rules are specifically not designed to simulate physics'. The word physics itself (as far as my control-find search can tell) is not to be found in the 5e PHB, and occurs in the DMG just once, and not paired with the idea of whether the rules are attempting to simulate it.

Thus while the idea that the game is not simulationist can be found in the rules, the pithy phrase 'D&D is not a physics simulator' is not there, as far as I can tell.

On the other hand, Exempt-Medic (and follow the link to chat) points out that Jeremy Crawford has said multiple times in tweets that the rules are not meant to simulate physics. The fact that Crawford has said this repeatedly (rather than simply citing the rule itself) further suggests to me that you will not find such a statement in the rules.

Fantasy is filled with symbolism. In a fight, only the extraordinary can harm a lycanthrope. It's not physics (Jun 2016)

Indeed. D&D is not a physics engine. (Dec 2016)

Nothing in the rules causes a fireball to vaporize water. Magic ≠ physics. DMs may apply whatever magical/scientific logic they like. (Feb 2017)

The earliest uses of the phrase I have found on this site with questions tagged as 5e come in the fall of 2017, with this the first one:

"D&D is not a physics simulator, and never intended to be." (Sept 2017) From that point on, the phrase becomes increasingly common in 5e questions and answers.

So, to your question: How does one justify this response to problems as it is often presented without justification, and what support for this claim is present in the actual rules?

The claim that the 5e rules say, sensu stricto, that 'D&D is not a physics simulator' is false. The rules are certainly informed by the spirit that they are not attempting a simulationist approach to many real world processes, and this far predates 5e.

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  • \$\begingroup\$ @Kirt JC also very clearly makes 'rulings' that disagree with the rules. Making JC less than useful. \$\endgroup\$
    – NautArch
    Mar 17 at 14:54
  • \$\begingroup\$ +1 I like this answer - it is the one most clearly resolving the question in the narrow context of 5e (as it was posed). I'm unfortunately only able to accept one answer. Thank you for adding this, I think it helps to understand the situation for the question overall. \$\endgroup\$ Mar 17 at 15:35
  • \$\begingroup\$ @NautArch I certainly agree with that. Personally I ignore JC for RAW, but consider him for RAI when I think RAW is unclear. However, in this particular case I am not using him for either one, but simply to attempt to establish that the rules actually don't address this. The validity of his rulings in any of these tweets is inconsequential - what is relevant is that he is implying (I think) that the rules themselves never explicitly say that D&D doesn't attempt to simulate physics. \$\endgroup\$
    – Kirt
    Mar 17 at 17:18
  • \$\begingroup\$ I think it's fine to argue "the rules don't address this, but it's just a reasonable interpretation of how the game works" – I just don't think "Crawford tweeted this, which must mean the rules don't address it" is a compelling argument. \$\endgroup\$
    – V2Blast
    Mar 18 at 17:22
  • \$\begingroup\$ @V2Blast "must" is a strong word; I don't think I am making that argument and wouldn't find it compelling either. I do think pointing out that JC has addressed this multiple times in a way that implies (qualifier) the rules don't might be valuable for some people (qualifier). YMMV - and apparently does, which is fine. \$\endgroup\$
    – Kirt
    Mar 18 at 17:34

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