Main idea

Dunbar's number, often summarized as a limit on the number of stable social relationships a person can maintain, concerns social relationships — and its generalization into a single human number has itself been contested. It says nothing about the number of ideas you can keep active.

It can still serve: not as proof, but as a displaced intuition. What we want to actively maintain probably has to stay bounded. Hence a personal limit — two hundred cards — set as a constraint to test, not as a demonstrated result.

The borrowing is legitimate as long as its status is explicit. What makes it abusive isn't the displacement itself, but taking the authority of the field of origin along with it to validate a hypothesis that hasn't been tested.

Why it matters

It gives an honest way to use a reference outside its field, which is very common in method articles: you keep the intuition, you leave the proof where it is.

It also illustrates what a practice of confronting ideas does: move knowledge from one field toward another problem in order to draw a personal hypothesis from it.

Nuances and limits

A displaced intuition remains an intuition: it steers an experiment and never replaces observing what happens when the constraint is reached.

Open questions

Is a constraint set by borrowing revised as easily as any other, or does the authority of the field of origin make it harder to abandon?