How can I resolve the contradictory rules on what tests can be substituted with Mouse Nature?

Mouse Guard p. 232: under “Acting with Your Nature”, the rules say “When action in the game involves escaping, climbing, hiding or foraging, you can roll your Nature instead of a skill at no cost.” No problem there.

Mouse Guard p. 233: under “Acting Against Your Nature”, the rules say “If your character is in a situation that is against his Nature — fighting, researching, arguing, etc. — and doesn’t have the proper skill, he may make the test using his current Nature rating.” The emphasis on “skill” is in the original.

Mouse Guard, p. 95: under “Beginner’s Luck”, the rules say “Nature can be used as a substitute for any ability or skill that you don’t have.”

On the Character Sheet, the “Nature Rules” say “Acting against Nature: Use Nature in place of any ability or skill, if test is failed, Nature is taxed by the margin of failure.” Again, the emphasis is in the original.

The main section on Nature contradicts the other parts of the rules on this. The Nature rules explicitly say that only a skill test can be substituted by Nature (whether acting with or against Nature); the other parts explicitly allow “any ability or skill” to be substituted by Nature, if acting against Nature. At least one of them needs to be fixed :-)

This is all separate from using a Persona to Tap Nature, which adds Nature to the dice rolled. That's not a problem, it's quite clear for me.

Instead, this is about substituting Nature for another rating. So what's the correct answer: What can Mouse Nature be substituted for?


For a literal reading, disregard what p. 95 says. "Beginner's Luck" is rules for what to do when you don't want to fall back on Nature and want to use a skill you don't have (and potentially earn the skill). The discussion of Nature there is just conversational preamble to put the Beginner's Luck rules into context.

That leaves a conflict between the rule on Nature and the character sheet. You can judge this conservatively, and say that the character sheet is trumped by the actual rule. So taking the text literally, Nature may only substitute for skills.

On the other hand, the spirit of the Acting Against Your Nature rule is that any time the mouse is doing something un-mouse-like, they may choose to substitute Nature for the roll. Since ability tests will sometimes be called for by the GM instead of skill tests, and since some of these circumstances may be against Mouse Nature, it would be rather mean of the rules to deny players the ability to substitute Nature when they're acting against their Nature just because the game didn't think of an appropriate skill for that situation beforehand.

So my considered answer is, "Is the mouse acting against their Mouse Nature? Then you can choose to substitute Nature for the roll."

Edit: In light of Luke Crane's answer linked in okeefe's answer, the former, literal interpretation is the right one. The key seems to be "a skill you don't have" when acting against mouse nature, and abilities aren't ever something the mouse doesn't have. So Nature can only substitute for skills that a mouse doesn't have.


I re-asked this on the Mouse Guard forum and got an answer from Luke Crane: The character sheet is incorrect.

  • 1
    \$\begingroup\$ Great! It's a pity Luke can't be more explicit in his online responses; he doesn't say what the correct interpretation is, only that “the character sheet is incorrect”. I guess we'll have to infer what the implications of that are. \$\endgroup\$ – bignose Sep 6 '10 at 22:53

Seven is right, but to answer more simply:

  • You use Beginner's Luck if you don't have a needed skill.
  • You use the Acting Against Nature rules when you're acting against your (mouse) nature.

There's no general way to substitute Nature for an ability (only when you're acting against your nature), though you can spend a persona point to add your Nature to other rolls (including ability rolls), whether or not something is for or against your nature.


Digging carefully through the rules...

page 232: if the action is within your nature you can substitute nature for a skill at no cost. Specifically excludes wises. (Note that this is important for both mice and weasels, who have different descriptors, but both of whom have skills and nature.)

page 233: Outside of the nature descriptors, you can substitute only for a skill you lack.

The Letter-sized Character Sheet: Luke said it was wrong. Ignore it. Actually, just cross out "ability or."

The Square Character Sheet (Boxed Set): has the wording "in place of a skill."

Page 95: the section on Beginner's Luck... it notes the one time you can roll Nature in place of an attribute: when, due to conditions (injury and/or illness) it has been reduced to 0. (right column, ¶5, with the icon bullet):

If an ability is at zero due to Injury or Sickness, you can not test it using Beginner's Luck at this time. You must use your Nature until you're recovered.

Since this is inside the section on Beginner's Luck, you're already looking to substitute a non-skill ability for a missing skill. If you have no attribute left to substitute you can't, and must instead use nature. No contradiction there. And it happens only rarely to PC's - you have to be both sick and tired and have either Will or Health at 2 to begin with. For starting characters, this means a Tenderpaw, who has Will 2.

Note also: the Nature rules apply to non-mice exactly the same, but substituting their species' descriptors for Escaping, Climbing, Hiding, and Foraging. This means that, since most creatures other than mice and weasels are not given will or health scores, they always substitute nature (complete with tapping).

Note Further: substituting nature does not earn experience towards gaining a new skill; it earns it for Nature.


First - to be clear.

1) Beginner's Luck is a wholly separate mechanism that just happens to also use Nature. It's purpose is to learn a new skill, not merely succeed at an action.

2) Second, I am assuming that your difficulty is with the question of whether or not Nature can be used in place of an ability check. Although you ask the question of what it can be used for more generally, it appears that you understand that it can be used for any skill check, regardless of whether that check is or is not within the mouse's nature (the difference, of course, being whether or not Nature is taxed upon failure).

With those two clarifications - can you propose a hypothetical action where an ability check would be used for an action outside of Mouse nature rather (than a skill check)?

Also, keep in mind that a strictly literal reading (which is how Luke Crane seems to encourage people to read his book) makes this moot. Nature can, by this reading, substitute for any skill or ability "you don't have". By definition, don't the mice have all abilities present in the rules and therefore this situation can never arise?


  • \$\begingroup\$ I'd love to take a literal reading. A literal reading leads to a contradiction, as shown in the question description. \$\endgroup\$ – bignose Sep 6 '10 at 11:28
  • \$\begingroup\$ There are many cases where an ability is tested. For example, a test to resist bad effects might test Health; or a tiebreaker roll might test Will or Health. If the mouse is Climbing or Escaping etc. at the time, the player would be right to ask if Nature can substitute for the rating. \$\endgroup\$ – bignose Sep 6 '10 at 11:29
  • \$\begingroup\$ On the contrary - a literal reading would require them to not have the ability they want to substitute for. \$\endgroup\$ – Syrsuro Sep 7 '10 at 5:17
  • \$\begingroup\$ -1: major factual error. Beginner's luck uses Will or Health, not nature. (Mouse Guard, p. 95.) The page 233 reference reading"This is not Beginner's Luck. The player may roll his ful current Nature rating, not half." isn't saying BL uses Nature, merely that the dice pool from Nature is not halved, unlike the BL pools derived from Will or Health. \$\endgroup\$ – aramis Dec 31 '11 at 5:45

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