“More or less at the same period, the problem of a real character was discussed in France, with a more skeptical attitude. In 1629, Father Marin Mersenne sent Descartes news of a project for a nouvelle langue invented by a certain des Vallées.
We are told by Tallemant des Réau that this des Vallées was a lawyer who had an immense talent for languages and who claimed to have discovered “a matrix language through which he could understand all others.”
All that was required to learn new meanings was a good dictionary, but learning a foreign grammar was more difficult. It might be possible, however, to obviate this difficulty by inventing a grammar that was free from the irregularities of natural languages, all of which had been corrupted through usage.
The resulting language would be a simplified one and might seem, in comparison to natural languages, the basic one, of which all the other natural languages would then appear as so many complex dialects.
It was sufficient to establish a set of primitive names for actions (having synonyms in every language, in the sense in which the French aimer has its synonym in the Greek philein), and the corresponding substantive might next be derived from such a name by adding to it an affix.
From here, a universal writing system might be derived in which each primitive name was assigned a number with which the corresponding terms in natural languages might be recovered.
However, Descartes remarked, there would remain the problem of sounds, since there are ones which are easy and pleasant for speakers of one nation and difficult and unpleasant for those of another.
On the one hand, a system of new sounds might also prove difficult to learn; on the other hand, if one named the primitive terms from one’s own language, then the new language would not be understood by foreigners, unless it was written down by numbers.
But even in this case, learning an entire new numerical lexicon seemed to Descartes a tremendous expense of energy: why not, then, continue with an international language like Latin whose usage was already well established?
At this point, Descartes saw that the real problem lay elsewhere. In order not only to learn but to remember the primitive names, it would be necessary for these to correspond to an order of ideas or thoughts having a logic akin to that of the numbers.
We can general an infinite series of numbers, he noted, without needing to commit the whole set to memory. But this problem coincided with that of discovering the true philosophy capable of defining a system of clear and distinct ideas.
If it were possible to enumerate the entire set of simple ideas from which we generate all the complex ones that the human mind can entertain, and if it were possible to assign to each a character–as we do with numbers–we could then articulate them by a sort of mathematics of thought–while the words of natural languages evoke only confused ideas.
“Now I believe that such a language is possible and that it is possible to discover the science upon which it must depend, a science through which peasants might judge the truth better than philosophers do today.
Yet I do not expect ever to see it in use, for that would presuppose great changes in the present order of things; this world would have to become an earthly paradise, and that is something that only happens in the Pays des Romans.”
It is true that, at the moment he wrote this letter, Descartes had not yet started his own research into clear and distinct ideas, as would happen later with his Discours de la methode; however, even later he never tried to outline a complete system of simple and clear ideas as the grounds on which to build a perfect language.
He provided a short list of primitive notions in the Principia philosophiae (I, XLVIII), yet these notions were conceived as permanent substances (order, number, time, etc.) and there is no indication that from this list a system of ideas could be derived (see Pellerey 1992a: 25-41; Marconi 1992).”
Umberto Eco, The Search for the Perfect Language, translated by James Fentress, Blackwell. Oxford, 1995, pp. 216-8.