Type/Token Distinction — A logical and metaphysical distinction introduced by Charles Sanders Peirce in the Collected Papers (particularly Vol. 4, §537, and Vol. 8, various sections; writings collected posthumously). Peirce observes that when one says the word “the” appears dozens of times on a page of text, “word” is being used in two senses: (1) the type — the word “the” as an abstract type or class, the single linguistic entity; and (2) the tokens — the particular, concrete instances or occurrences of that word on the page. The classic example: the sequence “cat cat” contains two tokens (two particular objects inscribed on the page) but only one type (a single type of word).
Technical Formulation
Peirce uses the terms “type” and “token”. The type is an abstract entity — a form, a pattern, a class. The token is a particular, concrete instantiation of a type: it occupies a place in space and time, and has physical properties (colour of ink, size, etc.). The relation between type and token is not the relation between a universal and its particulars (though it is analogous): it is a relation of instantiation. A type exists by virtue of there being (or being able to be) tokens that instantiate it.
Applications in Philosophy of Language
In linguistics and philosophy of language, the distinction is ubiquitous. Words are types; occurrences of words in texts are tokens. Sentences are types; utterances are tokens. This distinction has consequences for the theory of meaning: is meaning a property of types or of tokens? Generally of types — though tokens in particular contexts may acquire derived meanings (indexical, expressive).
The distinction also appears in the theory of music and the arts: a musical work (Beethoven’s Fifth Symphony) is a type, and each performance is a token. This observation, developed by Nelson Goodman in Languages of Art (1968), raises questions about artistic identity and authenticity.
Philosophy of Mind: Type-Type versus Token-Token Identity
In the philosophy of mind, the distinction is crucial for the debate about physicalism and the mind-body problem.
Type-type identity theory (U.T. Place, “Is Consciousness a Brain Process?”, 1956; J.J.C. Smart, “Sensations and Brain Processes”, 1959) holds that each type of mental state is identical to a type of physical (neural) state: pain = C-fibre firing (for example). This theory is strongly reductive.
Token-token identity theory (Davidson, “Mental Events”, 1970) holds that each particular occurrence of a mental state is identical to a particular occurrence of a physical state, but denies that mental types are identical to physical types. This position, anomalous monism, allows mental events to be physical without the mental vocabulary being reducible to the physical.
The type-type identity theory faces the problem of multiple realisability (Putnam, “Psychological Predicates”, 1967): the same mental type (pain) can be realised by very different physical types in different organisms (C-fibres in humans, other processes in octopuses). If pain = C-fibres, octopuses would not feel pain — which seems implausible. Token-token identity and functionalism are responses to this problem.
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