KAPLAN, DAVID
(1933–)

An American philosopher and logician, David Benjamin Kaplan was born in Los Angeles in 1933 and has spent his career mainly at the University of California, Los Angeles: first as an undergraduate student (AB in Philosophy, 1956; AB in Mathematics, 1957); then as graduate student (PhD in Philosophy, 1964), where he wrote the last dissertation Rudolf Carnap supervised; later as a faculty member, where he became Hans Reichenbach Professor of Scientific Philosophy in 1994.

Kaplan is best known for his work in formal semantics, particularly on the semantics of demonstratives and other indexicals: expressions such as this, that purple Mercedes convertible, I, you, here, now, and actually. In Demonstratives, Kaplan developed a theoretical framework in which sentences express propositions relative to contexts. The content of an expression (relative to a context C ) is what it contributes to the propositions expressed (relative to C ) by sentences that contain it. The content of an expression determines an intension: a function from circumstances of evaluation to extensions (truth-values for sentences, individuals for singular terms, sets of individuals for predicates). Circumstances include at least possible worlds and perhaps also times. The character of an expression determines a function from contexts to contents.

In this framework, indexicals have variable contents but stable characters. For example, relative to a context c whose agent is McX, I has a content x (which determines a function that maps every circumstance onto McX himself); whereas, relative to a context c * whose agent is Wyman, I has a different content y (which determines a function that maps every circumstance onto Wyman himself). But, relative to either context, I has the same character (which determines a function that maps c onto x and c * onto y ). Kaplan proposed that the character of an expression is its linguistic meaning and that it is an expression's character that is responsible for its cognitive value: The difference in cognitive value between "His pants are on fire!" and "My pants are on fire!," for example, lies in the difference between the characters of the indexicals his and my.

Indexicals are directly referential: For any context C, the content o of an indexical relative to C is the entity that the function determined by o maps every circumstance onto. For example, relative to c, whose agent is McX, the content of I is McX himself. Because indexicals are directly referential, a sentence that contains an indexical expresses a singular proposition (relative to a context C ): a proposition that contains the entity that is the content of that indexical (relative to C ). For example, relative to c, whose agent is McX, "I'm right" expresses a proposition that contains McX himself. This proposition can be represented as the ordered pair 〈McX, the property being right〉.

One surprising feature of this framework is that it allows one to distinguish logical truth and necessity. For example, "I am here now" is a logical truth in something like the following sense: Relative to any context C, it expresses a proposition that is true relative to the circumstance of C (at least provided that the agent of C is located at the time and place of C at the circumstance of C ). But, at least relative to most contexts, the proposition expressed by "I am here now" is not necessary: It is not true relative to every circumstance (likewise for "I exist" and "ϕ if and only if actually ϕ").

Kaplan's philosophical thought has moved from Fregeanism to Russellianism. In his 1964 dissertation, Foundations of Intensional Logic, Kaplan developed a Carnapian model-theoretic semantics for Alonzo Church's Fregean logic of sense and denotation. In "Quantifying In " (1968–1969), Kaplan developed a Fregean account of belief ascriptions and of belief, one that allows quantification into belief ascriptions (as in "There is an x such that Ralph believes that x is a spy") under certain circumstances. By Dthat (1978) Kaplan had turned away from his early Fregeanism toward a Russellian view on which "John is suspicious," for example, expresses a singular proposition, one that contains John himself and that can be represented as the ordered pair 〈John, the property being suspicious〉.

Kaplan went on to become a major proponent of the previously moribund theory of singular propositions. His Russellianism reached its apogee in Demonstratives (1989a), where he argued that indexicals are directly referential and, hence, that sentences containing indexicals express singular propositions. Although, in his 1989 Afterthoughts, Kaplan admitted to feeling "a resurgence of atavistic Fregeanism," he continued to treat indexicals as directly referential.

After Demonstratives and Afterthoughts, Kaplan has worked on a number of further topics. In Words, he argued that the relation between a word and its occurrences should be thought of as the relation, not between a type and its tokens, but rather between a perduring entity and its temporal parts. He also suggested that it is a word itself that is responsible for its cognitive value: The difference in cognitive value between "Hesperus equals Hesperus" and "Hesperus equals Phosphorus," for example, lies in the difference between the words Hesperus and Phosphorus. In work on expressives (expressions such as ouch and oops ), Kaplan suggested that one should shift from a semantics that pairs expressions with entities (meanings ) to a semantics that pairs expressions with rules for their correct use. Kaplan also suggested that characters might best be understood, not as entities, but rather as such rules.

See also Logic, History of; Philosophy of Language.

Bibliography

primary works

"Quantifying In." Synthese 19 (1–2) (1968–1969): 178–214.

"Dthat." In Syntax and Semantics. Vol. 9, edited by Peter Cole. New York: Academic, 1978.

"Demonstratives: An Essay on The Semantics, Logic, Metaphysics, and Epistemology of Demonstratives and Other Indexicals" [1977]. In Themes from Kaplan, edited by Joseph Almog, John Perry, and Howard Wettstein. Oxford: Oxford University Press, 1989a.

"Afterthoughts." In Themes from Kaplan, edited by Joseph Almog, John Perry, and Howard Wettstein. Oxford: Oxford University Press, 1989b.

"Words." Supplement to the Aristotelian Society 64 (1990):93–119.

Ben Caplan (2005)