Saying the Same Thing

In ordinary English, we use the terms "sentence," "statement" and "proposition" interchangeably but for some technical purposes we'll want to distinguish between them. In particular, when it comes to deciding when people are "saying the same thing," let us distinguish between the question of whether they are uttering the same sentence, making the same statement or expressing the same proposition.

Note: on the following account sentences, statements and propositions are not three different kinds of things: rather the question of whether we have the same sentence, same statement or some proposition suggest different ways of counting the same things.

A sentence is a linguistic entity, a creature of language, consisting of words of a language arranged according to the grammatical conventions of that language. People use sentences to do a variety of jobs, e.g. to ask questions, make promises, give orders and make statements. Sentences that make statements, typically declarative sentences, have truth value in virtue of the truth value of the statements they make. Not all meaningful sentences have truth value however, e.g. questions may have "yes" or "no" answers but they aren't, strictly speaking, true of false; orders may be obeyed or disobeyed but they aren't, literally, true or false.

Type and Token: In counting sentences, we can count by token or by type. Consider

(1) John is Paul's brother

(2) John is Paul's brother

In one sense I said the same thing in (1) and (2): they are the same type sentence, that is, they consist of the same words in the same order. But they are not the same token sentence, that is, they aren't the very same physical object, but are different objects, occupying different places, consisting of different bits of ink (or pixels if you're reading this off the web site).

Propositions are what sentences express; they may be understood as the meanings of sentences, thus the sentences (1) and (2) above, since they mean the same thing, express one and the same proposition. Moreover, different sentence types may express the same proposition. (1), (2) and (3) express the same proposition.

(3) John is the male sibling of Paul.

Although (3) is not the same type (or token!) sentence as (1) and (2) it is synonymous with them: all three sentences have the same sense or dictionary meaning so they express the same proposition.
Conversely, sometimes the same sentence can have more than one meaning: sentences, like (4), which can express different propositions are ambiguous:

(4) Last night I shot an elephant in my pajamas.

Groucho Marx disambiguated (4) by adding, “What he was doing in my pajamas I’ll never know.”

Context Dependence: Some sentences are context dependent, that is, what they say depends upon the context in which they are said-- by whom they are said, the time or place at which they are said or other features of the speaker's situation. Consider the following sentences as stated on the days indicated:

(5) [stated Septermber 8, 20011] Today is Thursday.

(6) [stated September 9, 2011] Today is Thursday.

(7) [stated September 9, 2011] Yesterday was Thursday.

"Today is Thursday" is context-dependent: what it says, in one way, depends on when it is said. (5) says that September 8, 2011 is a Thursday; (6) says that September 9, 2011 is a Thursday. But in another way, insofar as (5) and (6) express the same proposition, they still say the same thing: they have the same sense or dictionary meaning. Confusing, isn't it?

To eliminate confusion between the two different ways of saying the same thing we introduce a fussy distinction between expressing the same proposition and making the same statement--and understand the latter as saying the same thing about the same thing. (5) and (6) are not about the same thing: (5) says something about the day September 8, 2011; (6) says the same thing about September 9, 2011. (5) and (6) aren’t talking about the same day so they make different statements, even though they express the same proposition, that is, have the same dictionary-meaning. But (7) makes the same statement as (5): although it expresses a different proposition from (5), it makes the same statement because it says the same thing about the same thing, namely that September 8, 2011 is a Thursday.

Sense, Reference and Indexicals

"Meaning" is ambiguous: when we think of the "meaning" of a word or expression what we usually have in mind is its sense or dictionary meaning. Sometimes, though (as when I say "I mean you!") the word "mean" means aboutness, or reference. English and other natural languages include a variety of indexicals, words whose reference changes systematically depending where, when, by whom or in what circumstances they are said. They make sentences in which they occur context-dependent. And when sentences are context-dependent you can have same proposition/different statement or different proposition/same statement. (1) - (3) are not context-dependent: they all express the same proposition and make the same statement wherever, whenever, in what circumstances and by whomever they are spoken. (5) - (7) are context-dependent: the statements they make depend on the context in which they are spoken, in particular, the date on which they are said.

What are tokens, types, propositions and statements?
Don't ask what types and tokens, statements and propositions "really" are! What are sentences types, statements and propositions really apart from individual sentences? Nothing. Talking about them as if they were objects alongside individual sentences is convenient but misleading. Instead we should think of counting by sentence token, sentence type, proposition and statement as different ways of counting the same items--which, depending on the objects under consideration, may or may not coincide, rather like counting a group of students by individual student, by major, by year or by age.

These ways of counting chop up the set of sentences into equivalence classes, sets of objects that we choose to treat as the same, or interchangeable, for various purposes. For money purposes a quarter, 25 pennies, 2 dimes and a nickle, etc. all count as the same, because when it comes to buying and selling they’re interchangeable—even though they aren’t counted as the same for numismatic (coin collecter’s) purposes,
When we count by token, each object, that is each sentence, is in a class by itself. When we count by type we group together sentences by shape to cut up the set of sentences in that way. Similarly, counting by proposition and by statement are ways of grouping sentences cut up the set of sentences in different ways.

Study Questions

1. In ordinary English "identical" and "same" are ambiguous: sometimes we mean same type, other times we mean same token. Give examples of situations in which we mean same type and situations in which we mean same token, e.g. what do we mean when we talk about "identical twins"?

2. Give an example of a situation in which different sentences can be used to express the same proposition. [synonomy]

3. Give an example of a situation in which the same sentence may be used to express different propositions. [ambiguity]

4. Give an example of a situation in which sentences that express the same proposition are used to make different statements.

5. Give an example of a situation in which sentences that express different propositions are used to make the same statement.