User:Peter Damian/Sense and reference
Background – Frege's early theory of meaning
Frege's developed his original theory of meaning in early works like the Begriffsschrift ('concept script') of 1879 and the Grundlagen ('foundations of arithmetic') of 1884. On this theory, the meaning of a complete sentence consists in its being true or false,[1] and the meaning of each significant expression in the sentence is an extralinguistic entity which Frege called its Bedeutung, which literally translates as 'meaning' or 'significance', but which has been rendered by Frege's translators as 'reference', 'referent', 'Meaning', 'nominatum' etc.
Frege split the sentence up into two parts, one which is complete in itself, and which is analogous to the argument of a mathematical function, the other of which contains an empty place, by analogy with the function itself. [2] 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. Thus Frege's 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.
Sense
Frege introduced the notion of Sense (German: Sinn) to accommodate difficulties in his original theory of meaning. First, if the entire significance of a sentence consists in its truth value, it follows that the sentence will signify the same if we replace (S&R p.32) a word of the sentence with one having an identical reference, hence an identical truth value. But this is not the sense: someone may think that 'the evening star is a body illuminated by the Sun' is true, but 'the morning star is a body illuminated by the Sun' is false. The thought corresponding to the sentence cannot therefore be the reference, but something else, which Frege called the sense of the sentence. Second, sentences which contain proper names that have no reference cannot have a truth value, since the reference of the whole is determined by the reference of the parts. But the sentence 'Odysseus was set ashore at Ithaca 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.