Gottlob Frege On Sense and Reference
According to our classical view, propositions like “The sun is shining” have one of two possible truth values. Either such a sentence has the value of being true or the value of being false. We wonder what we can read the value from, how it comes about, and what this value is. A possible answer can be found in Gottlob Frege’s essay On Sense and Meaning. There he comes to the conclusion that the meaning of a proposition is its truth value. The questions that arise are:
1.how does Frege come to this conclusion and why?
2. what is meaning at all?
And these I would like to answer, the last one first, because its answer is obviously indispensable for answering the second one.
What is meaning?
Meaning according to Frege is related to signs and is distinguished from sense, which is also related to signs. As signs Frege does not merely refer to
“written signs” or signs of sign language, but also names” and “word-connections”.1 By his own account, he restricts signs in his essay to proper names, and in that case the meaning of signs is limited to certain objects “in the broadest sense”. Other signs could have other meanings, which would then be terms or relations. However, proper names here are not to be understood in the usual sense either, but are understood more broadly as words or sequences of words that designate a single object. An example of this, which he himself does not give, might be “the President of the United States,” because without context there is only one President of the United States, the one currently in office. “The President of the United States” thus refers to one object, but is made up of four, and thus multiple, words.
From the meaning of a sign Frege distinguishes its sense. The sense is that which can be “grasped by anyone who has sufficient knowledge of the language or the whole of relations to which” the proper name belongs.2 To each sign corresponds exactly “one particular sense,” but the meaning of something can also consist of several signs. In the sign is the sense, what we understand by the sign, and from the sense is taken the meaning. So the meaning is not meaning according to everyday understanding, in which we understand by meaning all that,
what we associate with the sign. In indirect speech, which Frege calls “odd speech,” the meaning that the sentence rendered from direct speech has becomes the meaning of the sentence in indirect speech.3
How does Frege conclude that the meaning of a sentence is its truth value?
First of all, for Frege, the meaning of a sentence consists of the meaning of the signs that make up the sentence. In the sentence “Odysseus was set ashore deep asleep in Ithaca,” the lack of meaning of “Odysseus” is the reason why the whole sentence has no meaning.4 Moreover, Frege equates the relation of thought to truth with the relation of sense to meaning. This is because he holds that assertion sentences contain thoughts, and these thoughts in turn are the sense of the assertion sentence. They are therefore the sense because a sentence whose subject is replaced by a word with the same meaning and different sense can be taken as a new assertion sentence. The proposition “The morning star is a body illuminated by the sun” can be taken to be false even if “The evening star is a body illuminated by the sun” is found to be true, although “the morning star” and “the evening star” have the same meaning. The relation of thought to the true is presupposed by him without justification, whereas he provides justification for the relation of sense to meaning. This relation results from the fact that sense and meaning are both parts of a sign.
Frege says that the sense of a proposition is the thought which the proposition expresses, and he distinguishes thoughts from conceptions. It seems to me that the idea, so far as it emerges from the essay, is as good a candidate for being meaning as the thought. Indeed, it seems to me that Frege gives no reason why thought is the sense of a proposition. Similarly, there is no reason given for why the idea is not a suitable candidate.
Apart from that, I think that at least in the way we understand true and false statements in everyday life, one can also make just such statements about fictitious objects. According to Frege, this would not be possible. If I say, “Sherlock Holmes is a famous detective,” then I hold the statement to be true even if I am aware that Homes is a fictional person (and I suppose I am aware of that at this moment, with the existence of Sherlock Holmes or a real-life template for him actually being considered by some). I also think that if you asked about famous detectives and didn’t limit the crowd in such a way as to ask about non-fictional people, people would absolutely name Sherlock Holmes as a possessor of that property. That this is particularly probative, however, can again be disputed.
In any case, if we assume that such a proposition is true in that it is true of Holmes to be a famous detective and in that it is true of famous detectives that Holmes is one of them, then we have a problem with Frege’s model. For either we say Sherlock Homes exists in our reality and thus his sign and thus the complex sign of this particular propositional sentence has meaning. Or we say, no, Sherlock Holmes does not exist, he could not have been met in London in 1885, and the sign “Sherlock Holmes” has no Fregean meaning, hence neither does the sentence. In the latter case this would mean that a truth value is ascribed to the sentence, although the sentence has no meaning. Thus the Interpretation would not be the truth value of a sentence.