The Brain Attic

A theory of forgetting

In A Study in Scarlet, Watson is scandalised to learn that Holmes does not know the Earth travels round the Sun, and means to forget the fact now that he has heard it. Holmes explains: the brain is like a little empty attic, and the fool hauls in every scrap of lumber he meets, so that the knowledge which might be useful is crowded out or jumbled. The skilled workman is fiercely selective about what he stores, and keeps his tools in perfect order.

It is a doctrine of deliberate ignorance, and it sounds absurd until you notice it is a theory of expertise. Holmes knows nothing of literature or astronomy and everything about tobacco ash, soils, and sensational crime — because he has decided, in advance, what his craft will need.

Expertise is organised memory

Modern cognitive science broadly vindicates the instinct if not the crude picture of a fixed-size attic. What separates a chess master from an amateur is not raw processing but stored patterns — tens of thousands of recognised configurations that let the master see the board in meaningful chunks rather than individual pieces. The same is true of physicians, of firefighters, of detectives. Skill is compressed experience, indexed for instant recall.

Holmes solves the eerie death in The Lion's Mane not by reasoning but by memory — a description dredged up, hours later, from an obscure book he once read about a venomous jellyfish. The mind that curated well beats the mind that merely thinks hard.

The external attic

Holmes never trusts memory alone. He keeps great hand-indexed commonplace books — potted biographies of villains, notable cases, cuttings from the agony columns, the sailings of ships — an external memory he can consult in seconds. Under a single letter he can turn up a vampire legend, a forger, and a swindler on the same page. It is a database in leather covers, and it is the direct ancestor of every note-taking system and search index a knowledge worker lives by today.

The stocked mind and the good archive are the same idea in two media: don't try to hold everything, but know exactly where everything is.

Building your own

The oldest method for a stocked mind is the method of loci — placing what you must remember as vivid images along a familiar route, a technique orators used two thousand years before the first flashcard. Mycroft's Memory Palace files any list as absurd, unforgettable scenes along a walk through 221B and drills the route until recall is automatic; Sherlock's Mind Palace lets you build the spatial floor plan yourself on a full-screen canvas. Both are the brain-attic, furnished on purpose.