Aures sunt in oculis Teaching language to the deaf in John Wallis' and Johann K. Amman's thought

In 1741 Antoine Ferrein presented his research on the phonatory apparatus, by comparing it to a string instrument, rather than, as traditionally happened, to an air one. In his treatise, De la formation de la voix de l'homme, he used for the first time the term 'cordes' to refer precisely to the vocal folds, thus proposing a revolutionary model of the anatomy of the apparatus itself. A few years later, he was a member of the evaluation commission of Jakobo Pereire, a Franco-Spanish pedagogist who teached French to a deaf boy by means of the oralist method, that is the method which does not allow a child to sign and focuses only on teaching her to speak. The link between both anatomical and articulatory knowledge and their applications in teaching speech to deaf people had some important precedents. The Aristotelian theoretical system concerning communication and cognition of the animated beings, became a model for those who engaged philosophical and medical studies related to the phonic-acoustic channel and its role in cognitive development. These issues contributed to a deep change in the philosophical approaches to language: the research on the anatomy of the phonatory apparatus allowed a new paradigm (naturalism) to emerge and called into question the old one (conventionalism). The works by John Wallis ("De loquela sive sonorum formatione", 1653) and Johann K. Amman ("Dissertatio de loquela", 1700) can be placed in this wide and complex context. They conceived and practiced two different educational methods, which were discussed and evaluated not only by Ferrein but also by other learned people.