sortal

Definition and Basic Features

A sortal is a type of general term that classifies objects into kinds in a way that provides criteria for counting and identity. Paradigm examples are nouns such as “person,” “cat,” “table,” “planet”. To call a term sortal is to say that it tells us:

1. What counts as one of that kind (how to count its instances), and
2. When we have the same one again (how to reidentify it over time).

By contrast, expressions like “red,” “tall,” “metallic,” or “visible” are usually treated as non-sortal or characterizing predicates. They ascribe properties but, by themselves, do not say what is to be counted as one red or one tall—one must first know what is red or tall (a person, a car, a building).

The sortal/non-sortal distinction is closely associated with that between count nouns and mass nouns. Count nouns (e.g., “dog,” “chair,” “apple”) are typical sortals, while mass nouns (e.g., “water,” “sand,” “furniture”) generally are not, because they do not individuate their referents into discrete units without further specification (e.g., “a glass of water,” “a grain of sand”).

Sortals are also often understood as carrying or presupposing a principle of persistence: they indicate under what conditions an instance of the kind continues to exist or ceases to exist as that kind. For example, the sortal “person” is associated with some account of when one and the same person persists through change, whereas “red” alone offers no such guidance.

Historical and Theoretical Background

Although the word sortal is a product of 20th‑century analytic philosophy, the underlying concerns are related to earlier discussions of substance, kind, and individuation in Aristotelian and scholastic metaphysics. The modern term is most prominently associated with P. F. Strawson, especially in Individuals (1959), and with later work by David Wiggins, Michael Dummett, and others.

Strawson introduced the notion of a sortal to explain how our conceptual scheme structures the identification and reidentification of particulars. According to Strawson:

• Sortal expressions provide answers to “What is it?” questions (e.g., “It is a dog,” “It is a person”), and
• They are indispensable for making identity statements over time (“This is the same dog as the one we saw yesterday”).

On Strawson’s view, we cannot make sense of individual objects without classifying them under sortal concepts. For him, sortals are fundamental to the “conceptual scheme” within which we speak about and track objects in space and time.

Later authors refined the notion. David Wiggins tied sortals to the idea of real kinds and explored how sortal concepts underwrite necessary and sufficient conditions for the identity of things of that kind. Others, such as Peter Geach, emphasized the role of sortals in relative identity: the idea that identity claims such as “x is the same F as y” make sense only relative to a sortal F.

Within this tradition, several core theses are frequently discussed:

• Sortal dependence of identity: identity statements such as “x = y” are intelligible only where x and y fall under one or more sortals that provide criteria of identity.
• Sortal relativity: something can be one and the same F but not one and the same G (e.g., “the same ship” but not “the same collection of planks”), because different sortals impose different persistence conditions.

These ideas connect the study of sortals to long-standing metaphysical debates about substance, composition, and persistence through change.

Applications and Contemporary Debates

The notion of a sortal plays an important role in several areas of contemporary philosophy:

1. Philosophy of language and semantics
   In semantics, sortals are often treated as expressions whose meaning includes individuation and counting conditions. They are contrasted with:

   • Mass terms (“gold,” “milk”), and
   • Adjectival or relational predicates (“red,” “taller than”) that lack such conditions on their own.

   Semantic theories may use sortals to explain:

   • How singular terms (e.g., proper names, definite descriptions) manage to refer to objects.
   • Why certain combinations are grammatical and meaningful (“two cats” vs. “two waters”) unless mass terms are shifted to count uses (“two waters” = two servings or bottles of water).

2. Metaphysics and ontology
   In metaphysics, sortals are central to questions about identity over time, objecthood, and constitution. For instance:

   • The persistence criteria associated with “person” may differ from those of “human animal” or “brain,” generating classic puzzles of personal identity.
   • The relationship between an artifact and its matter (e.g., a statue and the clay it is made of) is sometimes analyzed via distinct sortals with different persistence conditions.

   Debates arise over whether:

   • Sortal concepts carve nature at its “joints” (tracking objective kinds), or
   • They primarily reflect conceptual or linguistic practice, with no deep ontological significance.

3. Logic and formal systems
   In logic, the idea of many-sorted logic or typed systems is sometimes compared to philosophical sortals. A formal language may have different “sorts” or “types” of variables (e.g., for numbers, sets, persons), with different domains and rules. While not identical to the philosophical notion, such formal distinctions are often illuminated by appeals to sortal concepts.

4. Cognitive science and categorization
   In cognitive science and developmental psychology, researchers study how children acquire kind concepts—terms such as “dog,” “ball,” or “person” that behave like sortals. The philosophical notion of a sortal informs hypotheses about:

   • How early in development children grasp criteria for counting objects of a kind.
   • Whether certain sortals (e.g., “object,” “agent”) are cognitively primitive or innate.

There is no consensus on all aspects of sortals. Critics question, for example, whether all identity statements must be made under a sortal, or whether criteria of identity can always be made explicit. Others argue that natural language categories are often fuzzy, challenging the idea that sortals must supply sharp, determinate conditions.

Despite such disagreements, the term “sortal” remains a widely used tool for discussing how language and thought structure the world into countable, reidentifiable kinds, and how those structures bear on issues of reference, objecthood, and persistence.