The person sorting old papers is deciding which future questions may still be answerable.

Sorting papers looks like tidying, and it is really setting the limits of what anyone will be able to find out later. A discarded letter, a date on the back of a photograph, or a name in a margin can be the only remaining route to a question nobody has thought to ask yet. The person with the bin bag holds more than they usually realise.

If you are working through a box like that, keep anything carrying a name, a date or a place, even when it seems dull. Nothing needs deciding in an afternoon, and a second box costs less than an answer you cannot recover.