In a letter dated 1629 to theologian, philosopher, and mathematician Marin Mersenne, philosopher, mathematician and physicist René Descartes proposed an artificial universal language, with equivalent ideas in different tongues sharing one symbol:
"Et si quelqu’un avait bien expliqué quelles sont les idées simples qui sont en l’imagination des hommes, desquelles se compose tout ce qu’ils pensent, et que cela fût reçu par tout le monde, j’oserais espérer ensuite une langue universelle, fort aisée à apprendre, à prononcer et à écrire."
"The notion of a universal language was based upon the idea of precisely cataloging the elements of the human imagination. The great advantage of such a language would be that it would represent everything 'distinctement.' Yet, the great problem faced by someone who wanted to create such a language was the nature of the human imagination itself. Although separate from the mind and reason, which were the foundations of Cartesian thought, the imagination nevertheless played an important role for Descartes. As he wrote elsewhere in the Meditations, the imagination not only conceptualized external things but also considers them, 'as being present by the power and internal application of my mind.' Imagination, in other words, produced the illusion of presence, figures appearing so that can the person can 'look upon them as present with the eyes of my mind.' As a result, Descartes remains highly suspicious of the imagination because it can produce appearances that have no corresponding reality. Descartes concluded his letter to Mersenne by dismissing hopes for a universal language or a real character as only being possible in a 'terrestrial paradise' or 'fairyland' because of the confused nature of signification and the variation of human understanding.
"Mais n’espérez pas de la voir jamais en usage; cela présuppose de grands changements en l’ordre des choses, et il faudrait que tout le Monde ne fût qu’un paradis terrestre, ce qui n’est bon à proposer que dans le pays des romans.
"A universal language that would work at the level of the imagination, describing the actual 'things' of the external world, could only produce uniform results in the perfection of Eden or the ideal of fiction. One should, instead, stick with the institution of geometry as a method of rationalizing nature, a divine language grounded upon the cogito’s transmission of being. Descartes ultimately remains skeptical about any possibility of using alternative language games aside from mathematics in the project of rationalizing the world" (Batchelor, The Republic of Codes: Cryptographic Theory and Scientific Networks in the Seventeenth Century  http://www.stanford.edu/dept/HPS/writingscience/Cryptography.html, accessed 01-22-2010).