[2.2.7.] The Sense and Reference of a Sentence.

 

Up to now Frege has limited his discussion of sense and reference to expressions that refer to single definite individuals, especially ordinary proper names, e.g., “Barack Obama” and “the Morning Star.”[1]

 

But he believes that the sense/reference distinction can be applied to declarative sentences, as well.

 

 

What is the sense of a declarative sentence?

 

The sense of a given declarative sentence is “the thought” expressed by it.

 

What does Frege mean by “thought”?[2]:

 

                So far we have considered the sense and reference only of such expressions, words, or signs as we have called proper names. We now inquire concerning the sense and reference for an entire declarative sentence. Such a sentence contains a thought. (p.23)

 

By a thought I understand not the subjective performance of thinking but its objective content, which is capable of being the common property of several thinkers. (p.32 n.7, emphasis added)

 

So according to Frege, the thought expressed by a sentence is not mental or subjective, but public, just like a sense.

 

He seems to mean by “thought” what contemporary philosophers call a proposition:

 

proposition (df.): what a set of synonymous declarative sentences have in common; e.g., the declarative sentences “Snow is white,” “La nieve es blanca,” and “Schnee ist weiss” have in common the proposition that snow is white.

 

So for Frege, the sense of the declarative sentence “Odysseus was set ashore at Ithaca while sound asleep” is the proposition that Odysseus was set ashore at Ithaca while sound asleep.

 

 

What is the reference of a sentence?

 

                We are … driven into accepting the truth value of a sentence as constituting its reference. By the truth value of a sentence I understand the circumstance that it is true or false. There are no further truth values. For brevity I call the one the True, the other the False. (24)

 

The reference of all true sentences is the same: it is the True.

 

Likewise, the reference of all false sentences is the same: it is the False.

 

But some declarative sentences have no reference. They are neither true nor false, and refer neither to the True nor to the False.

 

E.g., “Odysseus was set ashore at Ithaca while sound asleep.”

 

This sentence has a sense, namely, the proposition that Odysseus was set ashore at Ithaca while he was sleeping.

 

But the name “Odysseus” has no reference; i.e., there is no such person as Odysseus. Because of the sense expressed by this name (which is something like: the son of Laertes who ruled Ithaca and fought in the Trojan War), the name does not refer to anything.

 

Frege’s view is that if a sentence contains an expression that has no reference, then the sentence as a whole has no reference.

 

For Frege, this means that the sentence is neither true nor false.

 

[As we will soon see, this is a point on which Frege and Bertrand Russell disagree.]