The Knox Decalogue: Rules of the Golden Age Detective
The Knox Decalogue is a list written in 1929 by Ronald Knox, in an attempt to solidify the rules of golden age mystery novels. These are even today used by some authors, although several, even in the golden age(an age including Doyle, Christie and Carr to mention some) have broken. They are, however, still worth a look, and can be usefol both when writing a detective novel and when solving one. Remember that these rules are largely made to protect the reader, and make sure that the challenge the writer presents to the reader is a fair one.
Nr 1: “The criminal must be someone mentioned in the early part of the story, but must not be anyone whose thoughts the reader has been allowed to follow.”
This rule is meant to remove deus ex machinas in the mystery stories, something which several other rules touch upon. It is obviously annoying for the reader when you have been presented with a finite number of suspects, and you have spent hours pondering which of them have a motive, the opportunity, the resources, only to have the culprit be a guy living in the attic unknown to everyone. It should be mentioned that many Sherlock Holmes stories, the short ones printed in magazines, do not reveal the murderer until the end, this because these stories cover Holmes' methods of solving crimes, he find a cigar butt and a footprint which leads directly to the criminal. For the longer stories Doyle mostly followed this rule.
On the second part of this, Knox would admit that Christie had made several excellent mysteries where the thoughts of the murderer was partially known, and said that this was no problem as long as the author did not attempt to trick the reader with these thoughts.
Nr 2: “All supernatural or preternatural agencies are ruled out as a matter of course. To solve a detective problem by such means would be like winning a race o
This means to things: first, the murderer can not employ magic, the murder must happen by strictly natural means, so as to not confuse or trick the reader. This is part of the fair play. The second meaning is that the detective can not use any form of magic, precognition etc. The solution must be found logically, so that the reader can solve it with, or before, the detective, should the reader be smart enough.
Nr 3: “No more than one secret room or passage is allowable. I would add that a secret passage should not be brought in at all unless the action takes place in
Pretty straight forward, the hidden passage is a trick that should not be overused, and must not be a deus ex machina brought in at the final moment. An interesting version appears in the japanese sound novel Umineko no Naku Koro Ni, where it says that no hidden passages must appear, but “hidden passage” is defined as any the detective can not find. This last one has more of a focus on the aspect that we could assume endless passages that no one can find and thus cheaply solve any closed room mystery.
Nr 4: “No hitherto undiscovered poisons may be used, nor any appliance which will need a long scientific explanation at the end.”
Rule 4 deals with unknown poisons and scientific devices unknown to regular people. We can imagine a poison which makes the victim climb up on the roof and jump from it, dying that way. This would be almost impossible to guess for the reader. In the same way, a teleportation device, or just the lates weapon from the Pentagon might do incredible things, but it would be unfair to expect the reader to understand and be able to use them in his or hers reasoning. Note the use of “at the end”, implying that if these devices where thoroughly explained early in the book so the reader knows of their existence and exactly how they work, they may still be used.
Nr 5: “No Chinaman must figure in the story.”
Please remember that Chinaman was not considered offensive at the time. The meaning of the rule is, no stereotypical minorities may play a part in the novel, as they are a strong indication that the story itself is bad. Knox did mention that there were examples to the contrary, but mainly racial stereotypes are a bad sign. It can be said that having the murderer be a racial stereotype, and that the race is the only reason for the murder we get, is far below par for the culprits motives.
Nr 6: “No accident must ever help the detective, nor must he ever have an unaccountable intuition which proves to be right.”
This one fits with the second, the detective must solve the crime logically out of fairness to the reader. There is however the question of where to draw the line here. A detective solving the crime due to female intuition may be cheap, but usually some fault on the murderers part, not properly disposing of the murder weapon for example, is of great help to the detective, and hardly unfair. A sudden inspiration which leads the detective to new discoveries may not be uncalled for either, but the end reveal of the solution must only be based on logic, observation and real clues.
Nr 7: “The detective must not himself commit the crime. This applies only where the author personally vouches for the statement that the detective is a detecti
The detective, when we as Knox says have him presented as a hero, is the character the reader lives through and often identifies with, and thus is the last person the reader will suspect. It is unfair to take advantage of this. There can be made great books this way, but not in the classical detective genre, where the detective and the reader competing in solving a mystery first is the main focus.
Nr 8: “The detective must not light on any clues are not instantly produced for the inspection of the reader.”
One of the most important rules, nr 8 states that all clues must be shown to the reader when the detective gets them. If not, the detective has an unfair advantage, and it is quite easy to create an unsolvable mystery if the reader is not given the necessary clues to solve it. This is the most important rule, and a story can hardly be called a mystery if rule 8 is not followed. The trick to a good detective novel is to give the reader all the clues, and making assembling them correctly the real task.
Nr 9: “The stupid friend of the detective, the Watson, must not conceal any thoughts which pass through his mind; his intelligence must be slightly, but very sl
More of a hint for good writing than a rule, but it may be useful for the detective to have someone to explain everything to, and a character which can ask the obvious questions the reader may be wondering. Reading Walton’s thought processes can also be of great help to the reader. In Umineko no Naku Koro Ni this rule was replaced by “It is permitted for observers to let their own conclusions and interpretations be heard.” This was done to especially allow for bystanders to lie or misunderstand a given situation, without this being taken as unfair to the reader, and not unfair of the author to put lies and fake clues into the novel. I do not think anyone would object to this being allowed.
Nr 10: “Twin brothers, and doubles generally, must not appear unless we have been duly prepared for them.”
The last rule, and we once again turn back to forbidding deus ex machinas. Having a twin brother turning out to be the guilty one, after it seems the innocent brother had done it, is cheap if we were not told he had a twin brother. Knox also adds criminals with extreme skills in disguise, unless we have been prepared these must not appear. It is too easy, says Knox.
These are the ten rules from the golden age of mysteries, when detective novels was truly considered a game between reader and writer. The rules are mostly made with fairness between the two competitors in mind, not good storytelling, but they still touch upon many essential things even in modern mystery novels, and when done correctly, these rules can give birth to what mystery author Carr described as “The grandest game in the world.” Of course, he too would break the rules from time to time.
http://umineko.wikia.com/wiki/Knox's_Decalogue (which contains both Umineko's tweaked versions and the full original ones.