David Kaplan (philosopher)
Encyclopedia
David Benjamin Kaplan is an American philosopher and logician teaching at UCLA. His philosophical work focuses on logic
, philosophical logic
, modality
, philosophy of language
, metaphysics
, and epistemology. He is best known for his work on demonstrative
s, on proposition
s, and on reference
in intensional
contexts.
in 1964, where he was the last graduate student mentored by Rudolf Carnap
. His thesis was entitled "Foundations of Intensional Logic". His work continues the strongly formal approach to philosophy long associated with UCLA (as represented by mathematician-logician-philosophers such as Alonzo Church
and Richard Montague
).
In most years, Kaplan teaches an upper division course on philosophy of language
, focusing on the work of either Gottlob Frege
, Bertrand Russell
, or P.F. Strawson. He also teaches a related course on Kripke's
Naming and Necessity
. His lively lectures often focus on selected paragraphs from Russell's "On Denoting
" as well as Frege's "On Sense and Reference
."
Kaplan's insights center on two key distinctions, which may be seen as responses to the inability of Frege's semantics to deal with context-sensitivity in language. First, in place of Frege's categories of Sinn and Bedeutung (typically translated as "sense" and "reference"), Kaplan introduces the notions of character and content. The former is the linguistic
meaning of an expression, and the latter is the proposition
(or propositional component) expressed by an expression in a context. Second, Kaplan makes an explicit distinction between the context of an utterance and the circumstances of evaluation of the proposition expressed by an utterance. Context can be formalized as a set composed of a speaker, a place, a time, and a possible world (and, depending on the analysis of demonstratives, perhaps a set of either demonstrations or directing intentions). Circumstances of evaluation play a role very similar to possible worlds
in modal semantics.
From these rough distinctions, Kaplan then defines character and content more precisely. Character defines a function associated by convention with an expression, which takes contextual elements as arguments and yields content as values. Content, on the other hand, defines a function taking as arguments those elements of the circumstances of evaluation relevant to determining extension, and yielding the extension
(referent or truth-value) as a value.
Two more important notions can thus be defined. We can say that an expression is context-sensitive if and only if its character defines a non-constant function (i.e., just in case it yields different content-values given different context-element-arguments). An expression is context-insensitive if and only if its character defines a constant function. Also, the distinction between character and content breaks down in the case of context-insensitive expressions, and convention associates each such expression directly with a content.
On the other hand, an expression is directly referential just in case its content defines a constant function from circumstances of evaluation to extension. Kaplan also characterizes directly referential expressions as those that refer without the mediation of a Fregean Sinn, or as those whose only contribution to content are their referents. Thus, in the case of directly referential expressions, we can say that the distinction between content and referent breaks down.
Any singular term
is directly referential according to Kaplan. So the following intuitive picture emerges: the meaning of an indexical is a rule taking us from some part of the context to an expression, and the meaning of an expression is a bit of propositional content that determines the extension in each possible world.
Kaplan goes on to use this semantic scheme to explain phenomena concerning the relationship between necessary and a priori
truth. An utterance is said to be necessarily true just in case the content it expresses is true in every possible circumstance; while an utterance is said to be true a priori just in case it expresses, in each context, a content that is true in the circumstances that context is part of. So, "I am here now" is true a priori because each of the indexical expressions used ('I', 'here', 'now') directly refer to the speaker, location, and time of utterance. But the utterance is not necessarily true, because any given speaker might have been in at a different place at that time, given different circumstances of evaluation. On the other hand, "I am David Kaplan," as spoken by David Kaplan, is necessarily true, since "I" and "David Kaplan" (both directly referential expressions) refer to the same object in every circumstance of evaluation. The same statement is not true a priori, however, because if it were spoken in a different context (e.g., one with a speaker other than Kaplan), it might be false.
Another result of Kaplan's theory is that it solves Frege's Puzzle
for indexicals. Roughly, the puzzle here arises as indexicals are thought to be directly referential, i.e., they do not refer by means of a Fregean Sinn. However, Frege explains cognitive value in terms of Sinn. Thus the following problem emerges: The sentences "I am David Kaplan", spoken by David Kaplan, "he is David Kaplan", spoken by someone pointing at David Kaplan, and "David Kaplan is David Kaplan", spoken by anyone, all express the same content and refer to the same individuals. Yet each of the three has a different cognitive value (it is possible to rationally believe one while denying another). Kaplan explains this by associating cognitive value with character rather than content, thus remedying the problem. (There are problems with this approach, which Kaplan explores in "Afterthoughts".)
Kaplan's semantic theory faces a problem, however, with proper names, which seem both directly referential and context-insensitive. On Kaplan's account, this means that constant functions are defined by both a proper name's character and its content, which would imply that proper names have no meaning other than their reference. While this approach to proper names is not novel (John Stuart Mill
being an early advocate), Frege's Puzzle
is thought to cast doubt on any such account. Many philosophers have attempted to deal with this issue (notably Joseph Almog, David Braun, Michael Devitt
, John Perry
, Nathan Salmon
, Scott Soames
, and Howard Wettstein), but no solution has been widely accepted.
propositional attitude attributions. Such issues were made salient primarily by W.V. Quine in his "Quantifiers and Propositional Attitudes" (1956).
The phrase "quantifying in" comes from Quine's discussion of what he calls "relational" constructions of an existential statement. In such cases, a variable bound by an anterior variable-binding operator occurs within a non-extensional context such as that created by a 'that' clause, or, alternatively, by propositional attitude or modal operators. The "quantifying in" idiom captures the notion that the variable-binding operator (for example, the existential quantifier 'something') reaches into, so to speak, the non-extensional context to bind the variable occurring within its scope. For example (using a propositional attitude clause), if one quantifies into the statement "Ralph believes that Ortcutt is a spy," the result is (partly formalized):
(Ralph believes that x is a spy)
In short, Kaplan attempts (among other things) to provide an apparatus (in a Fregean
vein) that allows one to quantify into such intensional contexts even if they exhibit the kind of substitution failure that Quine discusses. If successful, this shows that Quine is wrong in thinking that substitution failure implies existential generalization failure for (or inability to quantify into) the clauses that exhibit such substitution failure.
Logic
In philosophy, Logic is the formal systematic study of the principles of valid inference and correct reasoning. Logic is used in most intellectual activities, but is studied primarily in the disciplines of philosophy, mathematics, semantics, and computer science...
, philosophical logic
Philosophical logic
Philosophical logic is a term introduced by Bertrand Russell to represent his idea that the workings of natural language and thought can only be adequately represented by an artificial language; essentially it was his formalization program for the natural language...
, modality
Modality
-Humanities:* In law: the basis of legal argumentation in United States constitutional law* In theology: Modality : the organization and structure of the church, as distinct from sodality or parachurch organizations...
, philosophy of language
Philosophy of language
Philosophy of language is the reasoned inquiry into the nature, origins, and usage of language. As a topic, the philosophy of language for analytic philosophers is concerned with four central problems: the nature of meaning, language use, language cognition, and the relationship between language...
, metaphysics
Metaphysics
Metaphysics is a branch of philosophy concerned with explaining the fundamental nature of being and the world, although the term is not easily defined. Traditionally, metaphysics attempts to answer two basic questions in the broadest possible terms:...
, and epistemology. He is best known for his work on demonstrative
Demonstrative
In linguistics, demonstratives are deictic words that indicate which entities a speaker refers to and distinguishes those entities from others...
s, on proposition
Proposition
In logic and philosophy, the term proposition refers to either the "content" or "meaning" of a meaningful declarative sentence or the pattern of symbols, marks, or sounds that make up a meaningful declarative sentence...
s, and on reference
Reference
Reference is derived from Middle English referren, from Middle French rèférer, from Latin referre, "to carry back", formed from the prefix re- and ferre, "to bear"...
in intensional
Extensional
In philosophy of language, a context in which a sub-sentential expression e appears is called extensional if and only if e can be replaced by an expression with the same extension and necessarily preserve truth-value. The extension of a term is the set of objects that that term denotes.Take the...
contexts.
Biography
Kaplan received his Ph.D. in philosophy from UCLAUCLA Department of Philosophy
The UCLA Department of Philosophy is a constituent department of the Division of Humanities in the UCLA College of Letters and Science. From the mid-20th century, the department has been a leading and widely respected center for the study of Analytic Philosophy, especially Mathematical Logic,...
in 1964, where he was the last graduate student mentored by Rudolf Carnap
Rudolf Carnap
Rudolf Carnap was an influential German-born philosopher who was active in Europe before 1935 and in the United States thereafter. He was a major member of the Vienna Circle and an advocate of logical positivism....
. His thesis was entitled "Foundations of Intensional Logic". His work continues the strongly formal approach to philosophy long associated with UCLA (as represented by mathematician-logician-philosophers such as Alonzo Church
Alonzo Church
Alonzo Church was an American mathematician and logician who made major contributions to mathematical logic and the foundations of theoretical computer science. He is best known for the lambda calculus, Church–Turing thesis, Frege–Church ontology, and the Church–Rosser theorem.-Life:Alonzo Church...
and Richard Montague
Richard Montague
Richard Merett Montague was an American mathematician and philosopher.-Career:At the University of California, Berkeley, Montague earned an B.A. in Philosophy in 1950, an M.A. in Mathematics in 1953, and a Ph.D. in Philosophy 1957, the latter under the direction of the mathematician and logician...
).
In most years, Kaplan teaches an upper division course on philosophy of language
Philosophy of language
Philosophy of language is the reasoned inquiry into the nature, origins, and usage of language. As a topic, the philosophy of language for analytic philosophers is concerned with four central problems: the nature of meaning, language use, language cognition, and the relationship between language...
, focusing on the work of either Gottlob Frege
Gottlob Frege
Friedrich Ludwig Gottlob Frege was a German mathematician, logician and philosopher. He is considered to be one of the founders of modern logic, and made major contributions to the foundations of mathematics. He is generally considered to be the father of analytic philosophy, for his writings on...
, Bertrand Russell
Bertrand Russell
Bertrand Arthur William Russell, 3rd Earl Russell, OM, FRS was a British philosopher, logician, mathematician, historian, and social critic. At various points in his life he considered himself a liberal, a socialist, and a pacifist, but he also admitted that he had never been any of these things...
, or P.F. Strawson. He also teaches a related course on Kripke's
Saul Kripke
Saul Aaron Kripke is an American philosopher and logician. He is a professor emeritus at Princeton and teaches as a Distinguished Professor of Philosophy at the CUNY Graduate Center...
Naming and Necessity
Naming and Necessity
Naming and Necessity is a book by the philosopher Saul Kripke that was first published in 1980 and deals with the debates of proper nouns in the philosophy of language. The book is based on a transcript of three lectures given at Princeton University in 1970...
. His lively lectures often focus on selected paragraphs from Russell's "On Denoting
On Denoting
"On Denoting", written by Bertrand Russell, is one of the most significant and influential philosophical essays of the 20th century. It was published in the philosophy journal Mind in 1905; then reprinted, in both a special 2005 anniversary issue of the same journal and in Russell's Logic and...
" as well as Frege's "On Sense and Reference
Sense and reference
Sinn and bedeutung are usually translated, respectively, as sense and reference. Two different aspects of some terms' meanings, a term's reference is the object that the term refers to, while the term's sense is the way that the term refers to that object.Sinn and bedeutung were introduced by...
."
Work
Kaplan's work is primarily focused on issues in the philosophy of language and logic. These ventures, however, sometimes take him into related issues in other fields, such as the philosophy of mind.Semantics for Indexicals and Demonstratives
Kaplan's most influential contribution to the philosophy of language is his semantic analysis of indexicals and demonstratives, which is outlined (in progressively greater detail) in a series of articles: "Dthat," "On The Logic of Demonstratives," "Demonstratives," and "Afterthoughts".Kaplan's insights center on two key distinctions, which may be seen as responses to the inability of Frege's semantics to deal with context-sensitivity in language. First, in place of Frege's categories of Sinn and Bedeutung (typically translated as "sense" and "reference"), Kaplan introduces the notions of character and content. The former is the linguistic
Linguistics
Linguistics is the scientific study of human language. Linguistics can be broadly broken into three categories or subfields of study: language form, language meaning, and language in context....
meaning of an expression, and the latter is the proposition
Proposition
In logic and philosophy, the term proposition refers to either the "content" or "meaning" of a meaningful declarative sentence or the pattern of symbols, marks, or sounds that make up a meaningful declarative sentence...
(or propositional component) expressed by an expression in a context. Second, Kaplan makes an explicit distinction between the context of an utterance and the circumstances of evaluation of the proposition expressed by an utterance. Context can be formalized as a set composed of a speaker, a place, a time, and a possible world (and, depending on the analysis of demonstratives, perhaps a set of either demonstrations or directing intentions). Circumstances of evaluation play a role very similar to possible worlds
Possible Worlds
Possible Worlds may refer to:* Possible worlds, a concept in philosophy* Possible Worlds , by John Mighton** Possible Worlds , by Robert Lepage, based on the Mighton play* Possible Worlds , by Peter Porter...
in modal semantics.
From these rough distinctions, Kaplan then defines character and content more precisely. Character defines a function associated by convention with an expression, which takes contextual elements as arguments and yields content as values. Content, on the other hand, defines a function taking as arguments those elements of the circumstances of evaluation relevant to determining extension, and yielding the extension
Extension (metaphysics)
In metaphysics, extension is, roughly speaking, the property of "taking up space". René Descartes defines extension as the property of existing in more than one dimension. For Descartes, the primary characteristic of matter is extension, just as the primary characteristic of mind is consciousness...
(referent or truth-value) as a value.
Two more important notions can thus be defined. We can say that an expression is context-sensitive if and only if its character defines a non-constant function (i.e., just in case it yields different content-values given different context-element-arguments). An expression is context-insensitive if and only if its character defines a constant function. Also, the distinction between character and content breaks down in the case of context-insensitive expressions, and convention associates each such expression directly with a content.
On the other hand, an expression is directly referential just in case its content defines a constant function from circumstances of evaluation to extension. Kaplan also characterizes directly referential expressions as those that refer without the mediation of a Fregean Sinn, or as those whose only contribution to content are their referents. Thus, in the case of directly referential expressions, we can say that the distinction between content and referent breaks down.
Any singular term
Singular term
There is no really adequate definition of singular term. Here are some definitions proposed by different writers:# A term that tells us which individual is being talked about....
is directly referential according to Kaplan. So the following intuitive picture emerges: the meaning of an indexical is a rule taking us from some part of the context to an expression, and the meaning of an expression is a bit of propositional content that determines the extension in each possible world.
Kaplan goes on to use this semantic scheme to explain phenomena concerning the relationship between necessary and a priori
A priori and a posteriori (philosophy)
The terms a priori and a posteriori are used in philosophy to distinguish two types of knowledge, justifications or arguments...
truth. An utterance is said to be necessarily true just in case the content it expresses is true in every possible circumstance; while an utterance is said to be true a priori just in case it expresses, in each context, a content that is true in the circumstances that context is part of. So, "I am here now" is true a priori because each of the indexical expressions used ('I', 'here', 'now') directly refer to the speaker, location, and time of utterance. But the utterance is not necessarily true, because any given speaker might have been in at a different place at that time, given different circumstances of evaluation. On the other hand, "I am David Kaplan," as spoken by David Kaplan, is necessarily true, since "I" and "David Kaplan" (both directly referential expressions) refer to the same object in every circumstance of evaluation. The same statement is not true a priori, however, because if it were spoken in a different context (e.g., one with a speaker other than Kaplan), it might be false.
Another result of Kaplan's theory is that it solves Frege's Puzzle
Frege's Puzzle
Frege's Puzzle is a puzzle about the semantics of proper names, although the title is also sometimes applied to a related puzzle about indexicals...
for indexicals. Roughly, the puzzle here arises as indexicals are thought to be directly referential, i.e., they do not refer by means of a Fregean Sinn. However, Frege explains cognitive value in terms of Sinn. Thus the following problem emerges: The sentences "I am David Kaplan", spoken by David Kaplan, "he is David Kaplan", spoken by someone pointing at David Kaplan, and "David Kaplan is David Kaplan", spoken by anyone, all express the same content and refer to the same individuals. Yet each of the three has a different cognitive value (it is possible to rationally believe one while denying another). Kaplan explains this by associating cognitive value with character rather than content, thus remedying the problem. (There are problems with this approach, which Kaplan explores in "Afterthoughts".)
Kaplan's semantic theory faces a problem, however, with proper names, which seem both directly referential and context-insensitive. On Kaplan's account, this means that constant functions are defined by both a proper name's character and its content, which would imply that proper names have no meaning other than their reference. While this approach to proper names is not novel (John Stuart Mill
John Stuart Mill
John Stuart Mill was a British philosopher, economist and civil servant. An influential contributor to social theory, political theory, and political economy, his conception of liberty justified the freedom of the individual in opposition to unlimited state control. He was a proponent of...
being an early advocate), Frege's Puzzle
Frege's Puzzle
Frege's Puzzle is a puzzle about the semantics of proper names, although the title is also sometimes applied to a related puzzle about indexicals...
is thought to cast doubt on any such account. Many philosophers have attempted to deal with this issue (notably Joseph Almog, David Braun, Michael Devitt
Michael Devitt
Michael Devitt is an Australian philosopher currently teaching at the City University of New York in New York City. His primary interests include philosophy of language, philosophy of mind, metaphysics and epistemology...
, John Perry
John Perry (philosopher)
John R. Perry is Henry Waldgrave Stuart Professor of Philosophy at Stanford University. He has made significant contributions to areas of philosophy, including logic, philosophy of language, metaphysics, and philosophy of mind...
, Nathan Salmon
Nathan Salmon
Nathan U. Salmon is an American philosopher in the analytic tradition, specializing in metaphysics, philosophy of language, and philosophy of logic.- Biography :...
, Scott Soames
Scott Soames
Scott Soames is a professor of philosophy at the University of Southern California. He specializes in the philosophy of language and the history of analytic philosophy...
, and Howard Wettstein), but no solution has been widely accepted.
Quantifying in
In his article "Quantifying In" (1968), Kaplan discusses issues in intensional and indirect (Ungerade, or oblique) discourse, such as substitution failure, existential generalization failure, and the distinction between de re / de dictoDe dicto and de re
De dicto and de re are two phrases used to mark important distinctions in intensional statements, associated with the intensional operators in many such statements. The distinctions are most recognized in philosophy of language and metaphysics....
propositional attitude attributions. Such issues were made salient primarily by W.V. Quine in his "Quantifiers and Propositional Attitudes" (1956).
The phrase "quantifying in" comes from Quine's discussion of what he calls "relational" constructions of an existential statement. In such cases, a variable bound by an anterior variable-binding operator occurs within a non-extensional context such as that created by a 'that' clause, or, alternatively, by propositional attitude or modal operators. The "quantifying in" idiom captures the notion that the variable-binding operator (for example, the existential quantifier 'something') reaches into, so to speak, the non-extensional context to bind the variable occurring within its scope. For example (using a propositional attitude clause), if one quantifies into the statement "Ralph believes that Ortcutt is a spy," the result is (partly formalized):
(Ralph believes that x is a spy)
- ["There is someone Ralph believes is a spy"]
In short, Kaplan attempts (among other things) to provide an apparatus (in a Fregean
Gottlob Frege
Friedrich Ludwig Gottlob Frege was a German mathematician, logician and philosopher. He is considered to be one of the founders of modern logic, and made major contributions to the foundations of mathematics. He is generally considered to be the father of analytic philosophy, for his writings on...
vein) that allows one to quantify into such intensional contexts even if they exhibit the kind of substitution failure that Quine discusses. If successful, this shows that Quine is wrong in thinking that substitution failure implies existential generalization failure for (or inability to quantify into) the clauses that exhibit such substitution failure.