In thephilosophy of language, the distinction betweensense andreference was an idea of the German philosopher and mathematicianGottlob Frege in 1892 (in his paper "On Sense and Reference"; German: "Über Sinn und Bedeutung"),^[1][2] reflecting the two ways he believed asingular term may havemeaning.

Thereference (or "referent";Bedeutung) of aproper name is the object it means or indicates (bedeuten), whereas itssense (Sinn) is what the name expresses. The reference of asentence is itsextension, whereas its sense is the thought that it expresses.^[1] Frege justified the distinction in a number of ways.

1. Sense is something possessed by a name, whether or not it has a reference. For example, the description "the largestinteger" is intelligible, and therefore has a sense, even though there is no individual object (its reference) to which the name corresponds.
2. The sense of different names is different, even when their reference is the same. Frege argued that if an identity statement such as "Hesperus is the same planet asPhosphorus" is to be informative, the proper names flanking the identity sign must have a different meaning or sense. But clearly, if the statement is true, they must have the same reference.^[3] The sense is a 'mode of presentation', which serves to illuminate only a single aspect of the referent.^[4]

Much ofanalytic philosophy is traceable to Frege's philosophy of language.^[5] Frege's views on logic (i.e., his idea that some parts of speech are complete by themselves, and are analogous to thearguments of amathematical function) led to his views on atheory of reference.^[5]

Frege developed his original theory of meaning in early works likeBegriffsschrift (concept paper) of 1879 andGrundlagen (Foundations of Arithmetic) of 1884. On this theory, the meaning of a complete sentence consists in its being true or false,^[6] and the meaning of each significant expression in the sentence is an extralinguistic entity which Frege called itsBedeutung, literally meaning or significance, but rendered by Frege's translators as reference, referent, 'Meaning', nominatum, etc. Frege supposed that some parts of speech are complete by themselves, and are analogous to thearguments of amathematical function, but that other parts are incomplete, and contain an empty place, by analogy with the function itself.^[7] Thus "Caesar conquered Gaul" divides into the complete term "Caesar", whose reference is Caesar himself, and the incomplete term "—conquered Gaul", whose reference is a concept. Only when the empty place is filled by a proper name does the reference of the completed sentence – its truth value – appear. This early theory of meaning explains how the significance or reference of a sentence (its truth value) depends on the significance or reference of its parts.

Frege introduced the notion of "sense" (German:Sinn) to accommodate difficulties in his early theory of meaning.^[8]: 965

First, if the entire significance of a sentence consists of its truth value, it follows that the sentence will have the same significance if we replace a word of the sentence with one having an identical reference, as this will not change its truth value.^[9] The reference of the whole is determined by the reference of the parts. Ifthe evening star has the same reference asthe morning star, it follows thatthe evening star is a body illuminated by the Sun has the same truth value asthe morning star is a body illuminated by the Sun. But it is possible for someone to think that the first sentence is true while also thinking that the second is false. Therefore, the thought corresponding to each sentence cannot be its reference, but something else, which Frege called itssense.

Second, sentences that contain proper names with no reference cannot have a truth value at all. Yet the sentence 'Odysseus was set ashore atIthaca while sound asleep' obviously has a sense, even though 'Odysseus' has no reference. The thought remains the same whether or not 'Odysseus' has a reference.^[9] Furthermore, a thought cannot contain the objects that it is about. For example,Mont Blanc, 'with its snowfields', cannot be a component of the thought that Mont Blanc is more than 4,000 metres high. Nor can a thought aboutEtna contain lumps of solidified lava.^[10]

Frege's notion of sense is somewhat obscure, and neo-Fregeans have come up with different candidates for its role.^[11] Accounts based on the work ofCarnap^[12] andChurch^[13] treat sense as anintension, or a function frompossible worlds toextensions. For example, the intension of ‘number of planets’ is a function that maps any possible world to the number of planets in that world.John McDowell supplies cognitive and reference-determining roles.^[14]Michael Devitt treats senses as causal-historical chains connecting names to referents, allowing that repeated "groundings" in an object account for reference change.^[15]

In histheory of descriptions,Bertrand Russell held the view that most proper names in ordinary language are in fact disguiseddefinite descriptions. For example, 'Aristotle' can be understood as "The pupil of Plato and teacher of Alexander", or by some other uniquely applying description. This is known as thedescriptivist theory of names. Because Frege used definite descriptions in many of his examples, he is often taken to have endorsed the descriptivist theory. Thus Russell's theory of descriptions was conflated with Frege's theory of sense, and for most of the twentieth century this "Frege–Russell" view was the orthodox view of proper name semantics.Saul Kripke argued influentially against the descriptivist theory, asserting that proper names arerigid designators which designate the same object in every possible world.^{[16]: 48–49} Descriptions, however, such as "the President of the U.S. in 1969" do not designate the same entity in every possible world. For example, someone other thanRichard Nixon, e.g.Hubert H. Humphrey, might have been the President in 1969. Hence a description (or cluster of descriptions) cannot be a rigid designator, and thus a proper name cannotmean the same as a description.^[17]: 49

However, the Russellian descriptivist reading of Frege has been rejected by many scholars, in particular byGareth Evans inThe Varieties of Reference^[18] and byJohn McDowell in "The Sense and Reference of a Proper Name",^[19] followingMichael Dummett, who argued that Frege's notion of sense should not be equated with a description. Evans further developed this line, arguing that a sense without a referent was not possible. He and McDowell both take the line that Frege's discussion of empty names, and of the idea of sense without reference, are inconsistent, and that his apparent endorsement of descriptivism rests only on a small number of imprecise and perhaps offhand remarks. And both point to the power that the sense-reference distinctiondoes have (i.e., to solve at least the first two problems), even if it is not given a descriptivist reading.

As noted above, translators of Frege have rendered the GermanBedeutung in various ways. The term 'reference' has been the most widely adopted, but this fails to capture the meaning of the original German ('meaning' or 'significance'), and does not reflect the decision to standardise key terms across different editions of Frege's works published byBlackwell.^[20] The decision was based on the principle ofexegetical neutrality: that "if at any point in a text there is a passage that raises for the native speaker legitimate questions ofexegesis, then, if at all possible, a translator should strive to confront the reader of his version with the same questions of exegesis and not produce a version which in his mind resolves those questions".^[21] The term 'meaning' best captures the standard German meaning ofBedeutung. However, while Frege's own use of the term can sound as odd in German for modern readers as when translated into English, the related termdeuten does mean 'to point towards'. ThoughBedeutung is not usually used with this etymological proximity in mind in German, German speakers can well make sense ofBedeutung as signifying 'reference', in the sense of it being whatBedeutung points, i.e. refers to. Moreover, 'meaning' captures Frege's early use ofBedeutung well,^[22] and it would be problematic to translate Frege's early use as 'meaning' and his later use as 'reference', suggesting a change in terminology not evident in the original German.

The Greek philosopherAntisthenes, a pupil ofSocrates, apparently distinguished "a general object that can be aligned with the meaning of the utterance” from “a particular object of extensional reference". According to Susan Prince, this "suggests that he makes a distinction between sense and reference".^[23]: 20 The principal basis of Prince's claim is a passage inAlexander of Aphrodisias' “Comments onAristotle's 'Topics'” with a three-way distinction:

1. the semantic medium, δι' ὧν λέγουσι
2. an object external to the semantic medium, περὶ οὗ λέγουσιν
3. the direct indication of a thing, σημαίνειν ... τὸ ...^{[24]: 518–522}

TheStoic doctrine oflekta refers to a correspondence between speech and the object referred to in speech, as distinct from the speech itself. British classicistR. W. Sharples citeslekta as an anticipation of the distinction between sense and reference.^[25]: 23

The sense-reference distinction is commonly confused with that betweenconnotation anddenotation, which originates withJohn Stuart Mill.^[26] According to Mill, a common term like 'white'denotes all white things, as snow, paper.^{[27]: 11–13} But according to Frege, a common term does not refer to any individual white thing, but rather to an abstract concept (Begriff). We must distinguish between the relation of reference, which holds between a proper name and the object it refers to, such as between the name 'Earth' and the planetEarth, and the relation of 'falling under', such as when the Earth falls under the conceptplanet. The relation of a proper name to the object it designates is direct, whereas a word like 'planet' does not have such a direct relation to the Earth; instead, it refers to a concept under which the Earth falls. Moreover, judging of anything that it falls under this concept is not in any way part of our knowledge of what the word 'planet' means.^[28] The distinction between connotation and denotation is closer to that between concept and object than to that between 'sense' and 'reference'.

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On Sense and Reference

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