Disquotational principle
Encyclopedia
The disquotational principle is a philosophical theorem
which holds that a rational speaker will accept "p" if and only if he or she believes p. The quotes indicate that the statement p is being treated as a sentence, and not as a proposition. This principle is presupposed by claims that hold that substitution fails in certain intensional
contexts.
Consider the following argument: Sally accepts the assertion that "Cicero
was a famous orator" while dissenting from the assertion that "Tully
was a famous orator". Cicero is Tully
To derive (3), we have to assume that when Sally accepts that "Cicero was a famous orator", she believes that Cicero was a famous orator. Then we can exchange Cicero for Tully, and derive (3). Bertrand Russell
thought that this demonstrated the failure of substitutivity of identicals in intensional
contexts.
In "A Puzzle about Belief," Saul Kripke
argues that the application of the disquotational theorem can yield a paradox on its own, without appeal to the substitution principle, and that this may show that the problem lies with the former, and not the latter. There are various formulations of this argument.
Suppose that Pierre, a Frenchman, believes that (1) "Londres est jolie" (that London is pretty), without ever having been to London. After saving up enough money, Pierre finally gets tickets to Londres and flies there. When he arrives at his destination, he finds no French speakers (he does not speak English yet). Everyone refers to the city as "London," but not as Londres. He finds this city decidedly unattractive, for the neighborhood he decides to live in is decidedly unattractive. Over time, he learns English, and formulates the belief that (2) "London is not pretty". Pierre never realizes that London is the English word for Londres. Now with the disquotational principle, we can deduce from (1) that Pierre believes the proposition that Londres est jolie. With a weak principle of translation (e.g., "a proposition in language A is the same as a semantically identical proposition in language B" [note that a proposition is not the same as a sentence]), we can now deduce that Pierre believes that London is pretty. But we can also deduce from (2) and the disquotational principle that Pierre believes that London is not pretty. These deductions can be made even though Pierre has made no logical blunders in forming his beliefs. Without the disquotational principle, this contradiction could not be derived, because we would not be able to assume that (1) and (2) meant anything in particular.
This paradox can also be derived without appeal to another language. Suppose that Pierre assents to the proposition that "Paderewski
had musical talent", perhaps having heard that this man was a famous pianist. With the disquotational principle, we can deduce that Pierre believes the proposition that Paderewski had musical talent. Now suppose that Pierre overhears a friend discussing the political exploits of a certain statesman, Paderewski
, without knowing that the two Paderewskis are the same man. Pierre's background tells him that statesmen are generally not very gifted in music, and this leads him to the belief that Paderewski had no musical talent. The disquotation principle allows us to deduce that Pierre believes the proposition that Paderewski had no musical talent. Using this principle, we have now deduced that Pierre believes that Paderewski had musical talent, and does not believe that Paderewski had musical talent, even though Pierre's beliefs were formed logically.
Theorem
In mathematics, a theorem is a statement that has been proven on the basis of previously established statements, such as other theorems, and previously accepted statements, such as axioms...
which holds that a rational speaker will accept "p" if and only if he or she believes p. The quotes indicate that the statement p is being treated as a sentence, and not as a proposition. This principle is presupposed by claims that hold that substitution fails in certain intensional
Intensional
Intensional* in philosophy of language: not extensional. See also intensional definition versus extensional definition.* in philosophy of mind: an intensional state is a state which has a propositional content....
contexts.
Consider the following argument: Sally accepts the assertion that "Cicero
Cicero
Marcus Tullius Cicero , was a Roman philosopher, statesman, lawyer, political theorist, and Roman constitutionalist. He came from a wealthy municipal family of the equestrian order, and is widely considered one of Rome's greatest orators and prose stylists.He introduced the Romans to the chief...
was a famous orator" while dissenting from the assertion that "Tully
Tully
Tully is a surname of Irish origin. The surname itself and its variants include; Tally, MacTully, Tilly and Flood, all of which can derive from several different unrelated Irish families such as; Ó Maoltuile, Taithligh, Mac Maoltuile, Ó Taithligh, and Mac an Tuile...
was a famous orator". Cicero is Tully
- Therefore, (3) Sally believes that Tully was a famous orator.
To derive (3), we have to assume that when Sally accepts that "Cicero was a famous orator", she believes that Cicero was a famous orator. Then we can exchange Cicero for Tully, and derive (3). 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...
thought that this demonstrated the failure of substitutivity of identicals in intensional
Intensional
Intensional* in philosophy of language: not extensional. See also intensional definition versus extensional definition.* in philosophy of mind: an intensional state is a state which has a propositional content....
contexts.
In "A Puzzle about Belief," Saul Kripke
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...
argues that the application of the disquotational theorem can yield a paradox on its own, without appeal to the substitution principle, and that this may show that the problem lies with the former, and not the latter. There are various formulations of this argument.
Suppose that Pierre, a Frenchman, believes that (1) "Londres est jolie" (that London is pretty), without ever having been to London. After saving up enough money, Pierre finally gets tickets to Londres and flies there. When he arrives at his destination, he finds no French speakers (he does not speak English yet). Everyone refers to the city as "London," but not as Londres. He finds this city decidedly unattractive, for the neighborhood he decides to live in is decidedly unattractive. Over time, he learns English, and formulates the belief that (2) "London is not pretty". Pierre never realizes that London is the English word for Londres. Now with the disquotational principle, we can deduce from (1) that Pierre believes the proposition that Londres est jolie. With a weak principle of translation (e.g., "a proposition in language A is the same as a semantically identical proposition in language B" [note that a proposition is not the same as a sentence]), we can now deduce that Pierre believes that London is pretty. But we can also deduce from (2) and the disquotational principle that Pierre believes that London is not pretty. These deductions can be made even though Pierre has made no logical blunders in forming his beliefs. Without the disquotational principle, this contradiction could not be derived, because we would not be able to assume that (1) and (2) meant anything in particular.
This paradox can also be derived without appeal to another language. Suppose that Pierre assents to the proposition that "Paderewski
Ignacy Jan Paderewski
Ignacy Jan Paderewski GBE was a Polish pianist, composer, diplomat, politician, and the second Prime Minister of the Republic of Poland.-Biography:...
had musical talent", perhaps having heard that this man was a famous pianist. With the disquotational principle, we can deduce that Pierre believes the proposition that Paderewski had musical talent. Now suppose that Pierre overhears a friend discussing the political exploits of a certain statesman, Paderewski
Ignacy Jan Paderewski
Ignacy Jan Paderewski GBE was a Polish pianist, composer, diplomat, politician, and the second Prime Minister of the Republic of Poland.-Biography:...
, without knowing that the two Paderewskis are the same man. Pierre's background tells him that statesmen are generally not very gifted in music, and this leads him to the belief that Paderewski had no musical talent. The disquotation principle allows us to deduce that Pierre believes the proposition that Paderewski had no musical talent. Using this principle, we have now deduced that Pierre believes that Paderewski had musical talent, and does not believe that Paderewski had musical talent, even though Pierre's beliefs were formed logically.