The gaps a list cannot show

A woman in Manama sells socks online. Plain ones, striped ones, a few with patterns, in children's and adult sizes. Her stock list is a single long column, sorted by the date each style arrived.

Every few weeks a customer asks for something she does not have, and each time she is surprised. The list looked complete. It was long, and every line on it was real.

The trouble is that a list kept in the order things happened can only tell you what is there. It cannot tell you what is not.

Lay the same stock out differently, with sizes across the top and colours down the side, and the picture changes at once. Navy runs all the way across. Grey stops at medium. There is nothing at all for small children in anything but white. The gaps were there the whole time. The column simply had no place to show them.

Most of the lists people keep are like her first one. Inboxes, notes, product pages, the running record of what a small business offers. They are ordered by date or by the alphabet because that order costs no thought. It is also the order least likely to reveal what is missing.

A grid asks for a little thinking first. You have to decide which two questions matter, size and colour, price and occasion, beginner and expert, before you can set them against each other. Choose well and the empty squares stand out without anyone having to hunt for them.

So the useful question is rarely whether a list is complete. A list always looks complete. The useful question is what shape the thing ought to have, and which parts of that shape are still bare.