A vision scientist's review of The Greek Coffin Mystery by Ellery Queen (1932)

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I don’t think mystery novels by Ellery Queen are popular in western countries anymore, but they are still read in Asia. When I was a PhD student, every time I had to travel from my home country Taiwan to the USA, I would buy an Ellery Queen novel at the airport bookstore. This way, I could land in LAX with a solved mystery. Ellery Queen novels are substantial books with very complex plots - perfect for long flights because uninterrupted concentration is needed to tackle them. However, I gave up on the classic The Greek Coffin Mystery in the middle of the book, because even a transatlantic flight was not enough for me to follow the Byzantine plot (or maybe the Chinese translation was too bad). I recently decided to pick it up again - this time reading the original English text.

The Greek Coffin Mystery is excessively complex. There are just too many characters, too many red herrings, too many false endings… too many everything. I’ve always wanted to use computers to generate a mystery novel with a plot that is entirely logical, but too intricate for any human reader to follow - just to make a point about the futility of detective novels. But why frustrate the readers if you could entertain them with complexity? The excessiveness is why the novel is so brilliant. The puzzles are endlessly inventive. I mean, a locked room locked inside a larger locked room? That’s just the first couple of chapters. I like the fact that several times in the novel, the seemingly flawless logical deductions of the detective proved to be wrong! This particular form of exquisite pain, well-known among math majors, can finally be experienced by the common reader. The Greek Coffin Mystery really is a masterpiece of Golden Age mystery.

However, I am not a reviewer of mystery novels. I want to comment on this particular novel, because it’s a rare case where vision science plays a key role in the deduction. Embarrassingly bad vision science, that is. Alas! The two writers behind the Ellery Queen nom de plume dared to use color vision as a plot device, without knowing the basics of color vision.

(spoilers ahead)

The plot actually involves not one, but two vision science topics (Didn’t I say that this novel has too many everything?). A rich old man was found dead in his office. Before he died, he suffered from blindness caused by ulcers. That sounds very unusual, but the authors didn’t make it up. I found a 2000 review paper stating that blindness following gastrointestinal haemorrhage is a rare but well-known condition. The mechanism is unclear. It’s important to note that this form of blindness is not always permanent, because the detective Ellery Queen reasoned that the old man must have recovered his vision, which he had kept as a secret. You see… he was planning to commit a murder, and being blind would be the perfect alibi.

How did Ellery come to this extraordinary conclusion? The old man, being blind, instructed his cousin to prepare his daily outfit with a written schedule. Ellery observed that on the day that the old man died, he wore a red tie, despite that the cousin was supposed to give him a green tie according to the schedule. The cousin must have made a mistake. However, the old man seemed to know that he was wearing a red tie, because he called his tailor to order the red tie that he was wearing. How could he know that the cousin picked the wrong color? Because he was not blind!! That’s impeccable mystery novel logic.

But that’s where the detective made a crucial mistake. He didn’t know that the cousin was color-bind! The novel says that the cousin was “afflicted with a common case of color-blindness in which he consistently see red as green and green as red.” Knowing this, the old man wrote “green” on the schedule to mean “red”. He knew that he was wearing a red tie as a blind person, because that was his intended color on the schedule.

Red-green color-blindness (Deuteranopia) does not works this way. Deuteranopes have trouble distinguishing certain shades of red and green. If the cousin was a deuteranope, when asked to pick a green tie, he would pick a red or a green tie at random. As the old man couldn’t tolerate uncertainties in his outfits, he wouldn’t trust a deuteranope to pick his clothes and ties. The type of color vision described in the novel does not exist in reality. If it does, the cousin’s behavior would be indistinguishable from “normal” color vision, and nobody will ever know that his color percept was different. Why? Because words like “red” and “green” are just labels that we use to differentiate one color percept from another. They are not intrinsically tied to the percept themselves. When the cousin was learning language, mommy said “Little Johnny, look at this red apple!”, although the cousin experienced a different color as mom, he would refer to his percept of green as “red”. The old man therefore would have to instruct the cousin to pick a red tie, not a green one. In philosophy of mind, this is called the “inverted spectrum argument”. It’s usually used to argue for a dualist understanding of mind/body relationship. I hadn’t expected to encounter it in a detective novel!

If you are interested in more detective stories involving perception, please take a look at a follow up post.