Main idea

If everything becomes a flash card, nothing is one any more. The deck draws its value not from what it contains taken one by one, but from the fact that getting in is hard: every card added dilutes the status of all the others.

Hence an order of magnitude, and it is low: a deck below two hundred cards stays a manageable core of thought; five hundred is an upper limit beyond which wariness is in order. Having more than five hundred pillars is almost a contradiction — a pillar is supposed to carry something, and a structure that counts that many is no longer a structure.

The result of overshooting is not a deck that is too big, it is an object that has changed nature: a secondary note base, smaller than the first, with exactly the same problem. Rarity is part of the value, because creating a card does not say "this idea is interesting" but "this idea is structural".

Why it matters

It gives an opposable criterion for refusal at the weakest moment, the one just after reading something very sound. The good argument is not that the idea is worthless, it is that letting it in costs the status of all the others.

And it says where to look to diagnose a setup that no longer works: at the volume, before the content.

Nuances and limits

The number is nothing like a measurement. Two hundred is an order of magnitude of manageability, not a demonstrated threshold, and what matters is that a limit exists more than what its value is.

And a deck can be too small: a handful of cards do not structure a way of seeing, they caricature it.

Open questions

• Should the limit be a fixed ceiling, or simply the obligation to take a card out in order to let one in?