One of the more exciting concepts in Saussure is the sound-image of a word. Why should the spoken word, which needs time for its expression, have a frozen image ?
Plato’s keyword ἰδέα (idea) may help us here.
The word idea comes from Greek ἰδέα, romanized: idea, ‘form, pattern’, from the root of ἰδεῖν idein, ‘to see’.[3]
I would like to use ἰδέα not to discuss the “meaning” of words —where it is also and more obviously relevant — but instead something “deeper” than that, which allows for a word to be a word.
Consider, for instance, the word “mother” in the context of spoken language ( remembering Saussure’s phonocentrism). Forget, for now, the meaning of this word. Consider instead its (oxymoronic) “sonic form.”
All the billions of the vocalizations of this word so far are plausibly unique. Mother has never been said in exactly the same way twice. Yet the word mother has been said in each case.
In his famous Course in General Linguistics, Saussure tells us that
[I]t is impossible for sound alone, a material element, to belong to language. It is only a secondary thing, substance to be put to use. A coin nominally worth five francs may contain less than half its worth of silver. Its value will vary according to the amount stamped upon it and according to its use inside or outside a political boundary. This is even more true of the linguistic signifier, which is not phonic but incorporeal —constituted not by its material substance but by the differences that separate its sound-image from all others.
Elsewhere:
The linguistic sign unites, not a thing and a name, but a concept and a sound-image. The latter is not the material sound, a purely physical thing, but the psychological imprint of the sound, the impression that it makes on our senses.
Finally:
Putting it another way, language is a form and not a substance (see p. 113). This truth could not be overstressed, for all the mistakes in our terminology, all our incorrect ways of naming things that pertain to language, stem from the involuntary supposition that the linguistic phenomenon must have substance.
I suggest that the sound-image as “form and not a substance” can be understood in terms of Plato’s ideas. Or, equivalently, Saussure’s sound-image is a promising way to understand Plato’s use of ἰδέα.
While Plato used ἰδέα in a more general way, is this special case if the sound-image helpful for understanding Plato’s emphasis more general on forms ?