Phase Sortal

Definition and Core Idea

A phase sortal is a kind of sortal term that applies only to a temporal stage or phase in the existence of something that persists through time. Typical examples include “child”, “adolescent”, “adult”, “puppy”, “caterpillar”, or “student.” These expressions classify how a persisting entity is at a certain time, rather than specifying what sort of thing it is in the most fundamental sense.

By contrast, a substance sortal (often simply called a basic sortal) such as “person”, “dog”, or “organism” is taken to provide:

• Criteria of identity: what counts as the same individual over time
• Persistence conditions: what changes an entity can undergo while remaining that very thing

On the widely used characterization, a phase sortal:

1. Applies only to entities that already fall under some more basic sortal (e.g., only a person can be a child; only a dog can be a puppy).
2. Does not by itself provide criteria for identity over time. Someone can cease to be a student while remaining the same person.
3. Typically has built‑in temporal limits: to be a child or puppy is to be in a bounded life-stage of some more fundamental kind of thing.

Thus, phase sortals function as classificatory tools for the life-history or role-history of substances rather than as the primary ontological categories in terms of which persisting individuals are counted and reidentified.

Historical Background and Key Theorists

The notion of a sortal has roots in early analytic philosophy of language and logic (e.g., in work influenced by Gottlob Frege and P. F. Strawson), where philosophers distinguished between sortal expressions (like “dog,” “table”) and more general or adjectival expressions (like “red,” “large”). Sortals were said to answer the question “How many?” by providing a principle for counting and individuating.

The more specific contrast between substance sortals and phase sortals is developed in late 20th‑century metaphysics:

• David Wiggins: In his influential work on identity and substance, Wiggins introduces and refines the idea that some sortals provide the fundamental criteria for identity (substance sortals), whereas others are phase sortals, tied to temporary conditions. For Wiggins, terms such as “child” or “adolescent” characterize phases of a substance that is fundamentally a person or human being. The underlying substance sortal — for example, “person” — grounds questions like “Is this the same individual as before?” while “child” does not.

• E. J. Lowe: Lowe elaborates a four-category ontology and emphasizes the dependency of phase sortals on more basic substance sortals. In his system, phase sortals like “adult” or “student” are dependent sortal concepts: they can be instantiated only by entities of an underlying substance sortal and cannot themselves serve as the ultimate bearers of identity conditions.

• Contemporary analytic metaphysicians: The phase–substance sortal distinction has become a standard tool in discussions of personal identity, material constitution, and the semantics of natural-kind terms. It is routinely used to clarify whether a given predicate is meant to track an entity’s fundamental kind (e.g., person, organism, artifact) or merely a stage, status, or role of that entity.

While there is broad agreement on the intuitive contrast, philosophers differ over how sharply the distinction can be drawn, and whether some terms may function as both phase and substance sortals in different theoretical contexts.

Applications and Philosophical Debates

1. Personal Identity

The concept of a phase sortal plays a prominent role in debates about personal identity over time. Many theorists maintain that:

• “Person” is a substance sortal, providing criteria for when we are dealing with the same individual over time.
• Terms such as “child,” “teenager,” “adult,” “patient,” or “student” are phase sortals, describing temporary conditions of that same person.

This allows philosophers to separate questions about who someone is from questions about what phase they are in. For example, a person can enter and exit the phase of being a “student” while remaining numerically the same individual. Proponents argue that this framework explains how we can undergo radical life-changes without thereby becoming a different person.

Critics, however, question whether the distinction can always be cleanly maintained. Some argue that what counts as a persisting person may itself be deeply tied to social or biological phases, blurring the line between substance and phase sortals.

2. Biological and Developmental Kinds

In the philosophy of biology, many familiar life‑stage terms — such as “embryo,” “fetus,” “larva,” “pupa,” or “adult organism” — are treated as phase sortals of more basic biological kinds like “human being” or “butterfly.” The same organism persists as it passes through these phases.

Debates arise over which biological descriptions are genuinely phase sortals and which might better be considered distinct substance sortals (for example, in cases of radical metamorphosis or asexual reproduction). Some philosophers hold that in certain biological contexts, our intuitive “phases” do more than merely describe stages: they may reflect different underlying criteria of individuation.

3. Social and Institutional Roles

Terms like “student,” “employee,” “citizen,” “spouse,” or “refugee” are often cited as paradigm phase sortals in social ontology:

• They presuppose some underlying entity (often a person).
• They are typically status-dependent and revocable.
• They usually do not specify independent criteria of identity (the same person can be a student at one time and not at another).

In contemporary work on the metaphysics of social kinds, the phase sortal framework is used to clarify how individuals move in and out of socially constructed roles while remaining numerically the same bearer of rights, obligations, and capacities. Some authors, however, argue that certain social statuses may be so central to identity that treating them merely as phases underestimates their ontological and normative weight.

4. Semantic and Logical Issues

The phase sortal/substance sortal distinction has implications for:

• Quantification and counting: we count persons or dogs as basic units, while we describe how many of them are in a given phase (e.g., “Three of the children are now adults”).
• Modal and temporal reasoning: phase sortals often come with built‑in temporal parameters (“x is a child at t”) and are thus closely connected to tenses and temporal operators in logic.
• Reference and sortal relativity: some metaphysicians argue that all identity statements are implicitly sortal-relative. Phase sortals then illustrate how the same entity can fall under multiple sortals with different associated criteria, raising questions about whether identity is absolute or always relative to a classification.

There is no settled consensus on whether phase sortals are a purely linguistic phenomenon (features of how we talk) or reflect deeper ontological structures (features of how the world itself is organized into substances and their phases). Proponents of a robust metaphysics of sortals treat the distinction as tracking real differences in kinds of entities and their persistence conditions. More deflationary views see phase sortals as semantic tools that help organize discourse about changing things, without committing to a heavy metaphysics of underlying substances.

Overall, the concept of a phase sortal provides a refined vocabulary for describing the relation between what something fundamentally is and the temporary ways it can be, and it continues to figure in discussions of identity, change, and classification across metaphysics, philosophy of language, and social ontology.