Reverse reasoning, for want of a better name, is something I've always found charming. What do I mean by 'reverse reasoning'? I'll give you an example from
British Children's Literature in Japanese Culture. In that book, I recount the life of Momoko Ishii, the great translator, editor, publisher, critic, librarian, novelist and general powerhouse of Japanese children's publishing in the twentieth century. As a young graduate in English literature she was working for the writer and publisher Kan Kikuchi when the prime minister, Tsuyoshi Inukai, was assassinated - an event that marked the country's descent into military government. Kikuchi was acquainted with Inukai's son, and recommended Ishii as someone who could organise the deceased prime minister's personal library. In this way she became friendly with the Inukai family, and happened to be in the house one Christmas Eve, where she was presented by Inukai Jr.'s two children with a copy of
The House at Pooh Corner, which they had been given by a friend recently returned from England but were of course unable to read. Ishii sat with them, translating as she went, and was overwhelmed by the experience to the extent that she devoted the rest of her life to children's literature. (This is the short version, of course.)
Anyway, later in the book, I write:
It is a sobering reflection that, if Tsuyoshi Inukai had not been assassinated, Momoko Ishii would not have become close to Ken Inukai’s family, would not have found the copy of The House at Pooh Corner under the Christmas tree and would quite possibly never have pursued a career in children’s books. To suggest that the world of Japanese children’s literature therefore owes Inukai’s assassins a debt would be perverse, but it is a striking example of the arbitrary consequences of human actions, especially when large enterprises depend disproportionately on the actions of a few individuals.
The 'perverse' conclusion I mention is what I would call 'reverse reasoning' (but surely there's a better name?). Another example: I used to tease my former lodger, Rei, by saying that she was only able to come to Bristol because Tokugawa Ieyasu won the battle of Sekigahara. The reasoning was that: Tokugawa was thus able to establish his capital at Edo, which created a demand for soy sauce, which the Kikkoman company (upriver at Noda) was able to supply, becoming rich in the process, and in due course the Kikkoman-dominated Noda chamber of commerce was able to fund the scholarship which paid for Rei's travel.
This way of reasoning, or rather the evident ropiness of it, is what makes some early detective stories creak a bit. (Yes, I'm thinking of the opening conversation in '
The Murders in the Rue Morgue', and if you didn't guess that you are no Dupin.)
Anyway, I was delighted to find recently that there's a Japanese expression that plays with the same phenomenon: "When the wind blows, the barrel makers prosper." Here, the sequence goes as follows:
The wind blows dust into the air.
The dust increases cases of blindness.
The increased numbers of blind people mean that there are more shamisen players (an instrument traditionally played by the blind).
The increased demand for shamisens (traditionally covered in cat skin) reduces the number of cats.
The lack of cats means that the number of rats increases.
The extra rats, lacking food, are reduced to chewing barrels.
This makes extra work for barrel makers, boosting their profits.
The real problem with this way of thinking is that it fails to recognise the assymetry between cause and effect. Look back down the garden of forking paths and you see the one route you took. From the other end, you are dazzled by infinite possibilities. This is why it's easier to analyse a completed chess game than it is to write a chess program. The branching factor is too high - and in life it's higher still.
Still, the thought of being able to analyse things forwards in the way we habitually analyse them backwards is certainly appealing. Presumably there is a 'proper' name for it, better than 'reverse reasoning' - but what might it be?