The Game Ladder and the Five Rules
By Nelson McKeeby
A Small System for a Large Game
When I began Negentropy in 1979, the formal rules were only a few pages long. I called the central task system the game ladder. The phrase did not mean character advancement, levels, or a sequence of increasingly powerful abilities. It meant a compact way to decide what happened when a character attempted something whose outcome was not already obvious. The game could contain medicine, engineering, agriculture, communications, travel, weapons, investigation, social problems, and unfamiliar technology without giving each subject its own mechanical system. The game ladder supplied a common method for handling uncertainty while the subject itself supplied the facts that made the decision meaningful.
That distinction was present from the beginning and became one of the most durable parts of the design. I did not think a rulebook needed to reproduce the whole world in numbers. If the question was whether a gasoline engine could run without fuel, the answer came from the engine, not from a die. If the question was whether a physician could recognize a particular pattern of symptoms under difficult conditions, there was genuine uncertainty and the rules could become useful. The same principle applied to climbing, shooting, repairing a radio, crossing a flooded river, persuading a frightened witness, or deciding whether a damaged bridge could carry a vehicle. The game ladder existed to manage the uncertain part of a real situation after the players and Game Master had established what the situation actually was.
This approach also explains why the rules could remain small while the body of Negentropy material became very large. The rules did not carry most of the information in the game. That information lived in maps, source articles, Scout manuals, Army manuals, equipment descriptions, stories, notes on people and places, and eventually entire books on subjects such as healing, engineering, communications, natural history, firearms, and investigation. The game ladder connected all of that information to play. It was a decision tool, not a substitute for knowledge.
The Game Ladder
The earliest version was written quickly and was not elegant prose, but the basic structure was already the same. A player described what a character intended to do. The Game Master considered the character, the circumstances, and the physical problem. Most actions did not require a roll. Some were so routine that failure had no useful consequence, while others were ordinary actions within the competence of the person attempting them. A roll became useful when the result was genuinely uncertain and when success or failure would change the situation. The d20 gave us a simple way to resolve that uncertainty without turning the procedure itself into the center of play.
I called this a ladder because tasks could be considered in broad bands of feasibility. At one end were things that presented essentially no problem. Moving upward were ordinary actions that could usually be accomplished, then actions whose outcome depended enough on circumstances to justify a test, then actions that were physically possible but highly unlikely. At the far end were things the established world simply did not permit. Over time I expressed these bands more clearly as the Five Rules: the Rule of Triviality, the Rule of Probability, the Rule of Possibility, the Rule of Improbability, and the Rule of Impossibility. The names became cleaner and the examples became better, but the job of the system remained task management.
The ladder also encouraged the Game Master to make a judgment before reaching for dice. That was important because a roll has meaning only when the underlying question has been framed correctly. A player saying, 'I repair the generator,' has not yet supplied enough information. The generator may have a loose wire, a burned winding, a shattered shaft, no fuel, a missing control module, or a type of failure the character has never seen. The Game Master and player first establish what can be observed, what the character knows, what tools and parts are available, and what outcome is being attempted. Only then is there a useful task to classify. The die resolves uncertainty inside that task; it does not determine what the machine is made of or invent parts that are not present.
The Rule of Triviality
The Rule of Triviality exists because many actions are too easy, too repeatable, or too inconsequential to deserve a test. People open doors, put on clothing, read familiar words, walk across ordinary floors, use tools they know how to use, and perform hundreds of small actions in the course of a day. A person can occasionally fumble one of these things in real life, but modeling every dropped spoon and missed doorknob does not create a better game. If a failed attempt changes nothing and the character can simply try again, rolling usually adds delay without adding information.
Triviality is therefore partly about consequence. A character crossing an ordinary room does not need a movement test. The same character crossing a room while the floor is collapsing, smoke has reduced visibility, and another person is shooting through the doorway is doing something physically familiar under conditions that make the outcome consequential. The action has moved out of triviality because the circumstances changed. This kept the rule tied to the described world instead of treating every named activity as permanently easy or permanently difficult.
I found this especially useful in a game about technically competent characters. Troubleshooters are selected because they know how to do things. A physician should not need to roll to use a stethoscope correctly, and an engineer should not need to roll every time a wrench is turned. Their competence enters play through what they can do routinely and what they can recognize without a dramatic test. Dice become more interesting when those competent people reach the point where conditions, missing information, time pressure, damage, or simple chance make the result uncertain.
The Rule of Probability
The Rule of Probability covers actions that are not trivial but are normally expected to succeed under ordinary conditions. A person who knows how to ride a horse can stay in the saddle while the horse walks along a good road. A trained radio operator can operate a working set on a known frequency. A mechanic can perform familiar maintenance with the correct tools. Failure is possible in an abstract sense, but the situation does not contain enough difficulty to make failure the useful expectation. The rule allows ordinary competence to remain ordinary.
Probability is important because a game can become distorted if every action is treated as an even contest between success and failure. Real competence does not work that way. Training changes the range of situations in which a person can operate reliably. Good equipment does the same. Preparation, time, assistance, and familiarity can turn a difficult task into an ordinary one. Injury, bad tools, darkness, haste, unfamiliar machinery, or hostile interference can move the same task in the other direction. The ladder therefore describes the task as it exists now, not as a permanent rating attached to a verb such as ride, repair, persuade, or shoot.
This also reduced the temptation to use rolls as a substitute for description. If a character has the relevant Knowledge, the proper equipment, enough time, and normal working conditions, the Game Master can often allow the action to succeed and move the story to the result. That result may create the next problem. Repairing a pump can reveal that the well is contaminated. Reading a map can show that the only bridge is gone. Diagnosing an infection can establish that the necessary medicine is unavailable. Competence moves the story forward because it produces information and consequences instead of repeated tests of whether a trained person can perform routine work.
The Rule of Possibility
The Rule of Possibility is where the d20 does most of its work. The action can be done, but the circumstances leave enough uncertainty that success and failure are both credible outcomes. This is the ordinary territory of meaningful task resolution. The Game Master can judge the task as relatively easy, moderate, or hard within that band, and the die provides a quick answer. The numerical expression has been cleaned up over the years, but the purpose has stayed simple: turn a real uncertainty into a result without pretending to calculate every variable that produced it.
The important step comes before the roll. A possible action has to be physically and situationally defined. A character may be able to climb a wall, but height, surface, weather, equipment, fatigue, injury, lighting, and the need to move quickly all change the problem. A shooter may be able to hit a target, but range, visibility, movement, cover, weapon condition, and preparation change the chance. A chemist may know the reaction needed to identify a substance, but contaminated glassware or poor reagents can make the test uncertain. The Game Master does not need a separate modifier table for every one of these circumstances. The circumstances are considered together when deciding how difficult the actual task has become.
This is one reason I preferred a broad d20 system. Twenty possible results are enough to separate easy, moderate, and difficult uncertainty without creating an illusion of laboratory precision. The die does not mean that a task truly has exactly a thirty-five percent or sixty-five percent chance in the physical world. It gives the group a common randomizer after the important judgment has already been made. The description supplies the model; the d20 supplies variation.
The Rule of Improbability
The Rule of Improbability handles the edge of what can happen. Some actions are physically possible but so demanding that ordinary competence is not enough to make them reasonable expectations. A person may attempt an extraordinary jump, lift a weight near the limits of human performance, continue operating after severe exhaustion, or make a shot under conditions that leave very little margin for error. The action is not forbidden by the world, but success should be exceptional.
This category protects two things at once. It allows rare successes to occur, which is useful in adventure fiction, while keeping those successes rare enough that the physical world does not lose its shape. If every desperate action becomes an ordinary roll, players quickly learn that limits are decorative. If every extreme action is simply refused, the game loses the possibility of the remarkable event that everyone remembers afterward. Improbability gives those situations a place. The player can choose the risk with a clear understanding that the character is attempting something outside normal expectations.
The distinction also became important in post-game discussions because players often proposed actions that were cinematic in exactly this sense. A scene from a film might show a character making an enormous leap, continuing after an injury that should have ended the fight, or forcing machinery beyond its intended performance. Sometimes the underlying action remained possible enough to belong under Improbability. Sometimes closer examination showed that it crossed into impossibility. The game ladder made us ask which was actually true before deciding how dramatic the scene could become.
The Rule of Impossibility
The Rule of Impossibility is the hard boundary. If the established physical situation does not permit the result, there is no roll that can create it. A person cannot breathe indefinitely without oxygen, a battery cannot provide energy it does not contain, a bridge cannot support a load after the structure needed to carry that load has ceased to exist, and a weapon cannot fire ammunition it cannot chamber. The details can be exotic in Negentropy, especially when X technology, BEM biology, or Dwimmer is involved, but once those details are established they still create limits.
I considered this rule essential because a randomizer should resolve uncertainty, not repeal causation. A natural twenty is still a number on a die. It does not turn an impossible action into a possible one. This became particularly important with technology. Players would occasionally propose a device or use of equipment that sounded exciting but required more power, space, strength, heat tolerance, structural capacity, or material performance than the thing possessed. If research showed that the proposed result could not occur under the assumptions we were using, I preferred to change the plan instead of changing physics to reward the roll.
The Negentropic Cylinder itself produced this kind of argument. Cylinder volume was finite, so equipment had to fit. Pipe Cars were constrained by the motors, batteries, structure, and space available. Players repeatedly suggested larger Cylinders, unlimited power systems, or quantum devices that would remove those constraints. I usually rejected those solutions because the limits were generating useful decisions. If every limitation could be purchased away through a fictional technology, equipment selection would stop being a problem and much of the survival logic of the game would disappear.
Knowledges Instead of Classes
The game ladder worked with characters defined primarily by Knowledges. I did not use character classes or levels. The original Troubleshooter record grew from a school resume form used for internships, so I naturally thought about a character in terms of education, training, languages, experience, and what that person actually knew how to do. A geologist, physician, engineer, linguist, navigator, radio operator, or investigator approached a problem with a different body of knowledge even when all of them used the same Five Rules to resolve uncertainty.
Knowledges were not intended to become a disguised list of numerical skills. Their most important function was to establish what information a character could reasonably bring into the conversation. A person who understands electrical systems can recognize symptoms, ask better questions, choose useful tests, and avoid some mistakes before any roll occurs. A character without that Knowledge may still attempt a simple action after receiving instruction, but the player should not automatically receive the same interpretation of evidence. This makes knowledge affect the shape of the problem, not only the probability of passing a check.
That approach also encouraged teamwork. A Troubleshooter team could discuss a problem from several directions because no one character was expected to contain every useful body of knowledge. The engineer might understand why a pump has failed, the naturalist might recognize that the available water is biologically unsafe, the communicator might determine that a distant settlement can be reached by radio, and the investigator might discover that someone intentionally damaged the intake. The game ladder does not need separate mechanics for combining these contributions. The players combine them through conversation and planning, then use a task roll when the resulting plan reaches a genuine uncertainty.
Real Knowledge Supplies the Model
From the beginning, real reference material supplied much of the model behind those Knowledges. I used Boy Scout merit badge pamphlets, Army manuals, encyclopedias, USGS maps, technical books, interviews, and whatever other material I could obtain. If the game raised a question about growing food, I wanted to know what crops required. If it raised a question about electrical power, I wanted to know what motors, batteries, generators, and wiring could actually do. Medicine, communications, surveying, weather, geology, metalwork, vehicles, and weapons all entered the game in the same way.
The source articles that eventually became one of the defining features of Negentropy grew from this practice. They were written so that a player and Game Master could share enough information about a subject to make the situation intelligible. A healing article explains what injuries do and what treatment is trying to accomplish. An engineering article explains the machine and the failure. A communications article explains range, propagation, equipment, and procedure. Once the participants understand the system being represented, the Five Rules become easy to use because everyone is arguing about the same physical problem.
This is why I never saw a contradiction between a rules-light game and a large body of source material. The source material is not additional machinery attached to the rules. It is knowledge about the world. The small task system becomes more useful as that knowledge improves because the Game Master can make better judgments about what is trivial, probable, possible, improbable, or impossible. Adding another twenty pages of modifiers would not necessarily make the judgment better. Learning how the thing actually works often does.
Cinematic Reality and Concrete Reality
Once regular play began in 1980, our post-game discussions gave a name to a tension that had been present from the first design: cinematic reality and concrete reality. Cinematic reality follows the expectations of an exciting scene. It allows equipment, bodies, timing, and chance to cooperate because the sequence works dramatically. Concrete reality asks what the established situation can actually support. Neither phrase meant that a game had to be dull or that every session needed engineering calculations. They described two different standards for deciding what kinds of outcomes the group would accept.
I tended toward concrete reality when a problem depended on physical constraints. One of the earliest recurring arguments involved electrical power and the Pipe Cars. I had weighed equipment, worked through motor and battery questions, and even allowed X technology to improve performance. The cars still had limits. They consumed electricity quickly and could not become high-powered vehicles simply because that would make travel easier. Players suggested stronger fictional power sources and larger Cylinders. Those ideas would have produced more cinematic vehicles, but they would also have removed the problem I wanted the characters to manage: a small team had finite transport, finite power, finite cargo space, and no guarantee of replacement parts.
The Five Rules gave us a useful language for these disagreements. If an action was difficult but possible, the game could allow the attempt and let the d20 decide. If the action depended on a machine producing power it did not have, the problem was not difficulty. It was impossibility under the current assumptions. The players could still solve the problem, but the solution had to change something real in the situation: reduce the load, find another power source, repair the machine, change the route, acquire better equipment, or abandon the plan. That kind of problem solving was more interesting to me than using luck to make the original constraint disappear.
Why the Rules Stayed Small
The game ladder survived because it scales well. A new subject does not require a new core mechanic. If the campaign moves from agriculture to surgery, from a riverboat engine to diplomacy, or from radio direction finding to an unfamiliar BEM, the group still asks the same questions. What does the character know? What can be observed? What tools, time, assistance, and resources are available? What does the physical or social situation permit? Is the intended action routine, ordinarily likely, genuinely uncertain, exceptionally difficult, or impossible? Once those questions are answered, the rules have very little work left to do.
This also keeps attention on decisions. A complicated rule set can make mastery of the rules itself an important player skill. Negentropy was built around mastery of the situation. Players should benefit from understanding their equipment, asking good questions, noticing evidence, using the right person for the task, preparing before acting, and changing a plan when new information appears. A player who learns that the bridge is unsafe and chooses a ford has solved part of the problem before dice enter the scene. A player who determines that a patient is bleeding internally has changed the treatment problem before any healing roll is made.
The rules have been rewritten many times because early prose was rough and later books needed clearer examples, cleaner terminology, and better explanations for new readers. The underlying philosophy has changed very little. The Five Rules still exist because they describe a useful sequence of judgments. Trivial things normally happen. Probable things ordinarily happen when competent people attempt them under normal conditions. Possible things can be tested. Improbable things may succeed, but the attempt is exceptional. Impossible things remain impossible until something in the situation changes. The d20 resolves uncertainty inside that structure, while Knowledges and real information establish what the structure means in the scene being played.
The Rule System as a Boundary
Looking back, I think the most important function of the game ladder was not deciding success or failure. It established a boundary between rules and reality. The rules were allowed to answer questions that needed a random decision. They were not allowed to become the explanation for how medicine, machines, agriculture, weather, weapons, people, or societies worked. Those subjects had their own causes and constraints, and learning enough about them to make sensible decisions became part of the game.
That boundary is why the sourcebooks and the Five Rules developed together so naturally. The more accurately a sourcebook explains a subject, the less mechanical scaffolding is required to make that subject playable. If the players understand why a generator needs fuel, why a wound causes shock, why a crop needs water at a particular stage, or why a radio signal behaves differently at different frequencies, they can plan around those facts. The Game Master then uses the ladder where the plan encounters uncertainty. This keeps the story moving without turning the world into arbitrary narration or turning the rules into an encyclopedia of exceptions.
I began with a few typed pages because that was enough to make the game function. Decades of play have added procedures, examples, combat details, time scales, health rules, equipment, and thousands of pages of setting material, but the core remains recognizable. A player says what a character is trying to do. We establish what the character knows and what the world permits. Most ordinary actions simply happen. When the outcome is uncertain, we use the game ladder and the d20. When the proposed result is impossible, the player needs a different plan. That simple division of labor between knowledge, judgment, and chance has carried Negentropy from its first working model into the modern game.