sortals

A sortal is a term or concept that serves to individuate and reidentify entities of a certain kind. In ontology and philosophy of language, sortals are fundamental to understanding how we categorize and count things in the world. They provide the criteria for what counts as a distinct instance of a particular type. For example, "chair" is a sortal. When we ask "how many chairs are there?", the sortal "chair" tells us what to count. We don't count parts of chairs or collections of chairs as individual chairs unless specified.

Sortals are distinguished from non-sortal terms, such as "red" or "heavy." While we can say "this is red" and "that is red," we cannot ask "how many reds are there?" in the same way we ask "how many chairs are there?" unless we are referring to distinct instances of redness, perhaps in a collection of colored objects. Sortals impose a structure on our ontology, enabling us to distinguish between different kinds of objects and to track them through time and across different contexts.

The concept of sortals is closely related to the idea of individuation. A sortal provides the very criteria by which we individuate entities of a particular sort. Without sortals, it would be difficult, if not impossible, to make sense of numerical quantification and to distinguish one object from another of the same general type. Different philosophical theories offer varying accounts of the nature and role of sortals, but their importance in conceptualizing and reasoning about the world remains widely acknowledged.