 [I]t seems to me that determinates under the same determinable have a class unity […]. Determinates under the same determinable have the common relational property […] of characterising whatever they do characterise in a certain respect. Redness, blueness, etc., all characterise objects, as we say, “in respect of their color”; triangularity, squareness, etc., “in respect of their shape”. And this is surely quite fundamental to the notion of being a determinate under a determinable. (1949: 13)