A traditional ammeter shows the intensity of an electric current with the angular position of a pointer on a dial; in other words as a ratio of two lengths. A mercury or ethanol thermometer shows ambient temperature by the length of the column of liquid. A balance shows two bodies have different weights via the displacement of one pan below the other, producing a distance (or yet another length). It seems therefore that large numbers of physical properties are actually lengths. Or are they?
Areas of thought to help ponder: realism and instrumentalism; theory of properties; indicator hypotheses; social measurements; induction.

This article appears in the October 2019 version of Critical Links.