Sense and significatum
In actual linguistic communication, an utterance conveys a message in dependence on the linguistic context, the speech situation, the shared experience of the communication partners and their knowledge of the world. As long as mutual understanding arises, the question of which part of the content transmitted was coded by the signs constituting the message and which part was contributed by those environmental factors does not arise for the interlocutors. It is a question the linguist poses because its answer forms the core of a description of the language system. Describing all the above-mentioned pragmatic factors which contribute to form the sense of an actual message would be a limitless and unfeasible enterprise. Describing the language system is a huge, but solvable task.
This is the search for the significatum (de Saussure's signifié) of the linguistic sign. To identify it, the linguist strips the actual utterance of all those environmental components, isolating what Lyons (1977: $$) calls a ‘system sentence’. The system sentence is, to be sure, a linguistic construct, but one necessary for methodological reasons.
Imagine a situation in which is used as a true question, with the speaker pointing to an object he does not recognize.
| . | What is this? |
Then the sense of the expression this in might be taken to be “the object I am pointing to”. Now imagine a speech situation in which the speaker reacts with to an utterance just proferred by his interlocutor.
| . | This is pure nonsense. |
Then the sense of the expression this in might be taken to be “the proposition just proposed by you”. Depending on such external factors, the expression this may acquire countless different senses. Stripping the utterances of their conditions of use, what remains is the significatum of this, something like ‘the intended referent is in my proximity’. This is what is coded by this; and it applies to both and , while the more specific rest of the paraphrases given for the two uses is contributed by factors outside the language system.
In principle, the significatum of a linguistic sign is the greatest common denominator of all of its uses. However, this needs some qualification in the case of polysemy.