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The Ten Rules of Golden Age Detective Fiction

posted by Jason Kottke   Nov 23, 2021

The Golden Age of Detective Fiction describes a period between the world wars in which a certain style of murder mystery novel took hold, led by the prolific and talented Agatha Christie. Scott Stedman explains about the rise and fall of the genre in today’s issue of Why is this interesting?

It wasn’t until Agatha Christie introduced the world to Poirot that the genre shifted into its strictest and most enduring form: the garden variety murder mystery.

“I specialize in murders of quiet, domestic interest.” —Agatha Christie.

Agatha Christie is the most popular modern writer to ever live (outmatched in sales by only Shakespeare and the Bible). Christie is unrelenting in her ability to surprise — she killed children, popularized the unreliable narrator, introduced serial killers. Still, she was a fiercely disciplined adherent to a form created by her community of fellow writers, developed in the legendary Detection Club (including Dorothy Sayers, Ronald Knox, and the remarkable GK Chesterton). In an age sandwiched between two world wars — her stories brim with pride for a stiff British moral certitude that was impervious to the most heinous acts against it.

A central feature of many of these whodunits was that the reader had access to all the same information as the detective and could, in theory, figure things out before they did. In 1929, Ronald Knox wrote down 10 rules that made this possible:

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.

2. All supernatural or preternatural agencies are ruled out as a matter of course.

3. Not more than one secret room or passage is allowable.

4. No hitherto undiscovered poisons may be used, nor any appliance which will need a long scientific explanation at the end.

5. No racial stereotypes.1

6. No accident must ever help the detective, nor must he ever have an unaccountable intuition which proves to be right.

7. The detective must not himself commit the crime.

8. The detective must not light on any clues which are not instantly produced for the inspection of the reader.

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 slightly, below that of the average reader.

10. Twin brothers, and doubles generally, must not appear unless we have been duly prepared for them.

It’s interesting to see how these rules are applied and broken in TV and films these days. I feel like “hitherto undiscovered poisons” and “appliances which will need a long scientific explanation” (not to mention the “unaccountable intuition” of characters) are now regularly deployed, which can lead to feelings of being cheating as a viewer if it’s not done well. (via why is this interesting?)

  1. I follow Stedman here in restating this point…Knox’s original text used a derogatory term.