The long road to literacy for the blind includes Diderot's invocation for a ‘clear and precise language of touch’ (1916a: 90). In the century between the Lettre sur les aveugles of 1749 and the official adoption of Braille in France in 1854, previous attempts at raised script were consolidated, and a fateful meeting took place in 1784 between a blind musical prodigy named Maria Theresia von Paradis and Valentin Haüy, a talented linguist and avid reader of Diderot. During this period the role of the senses in education was the subject of much interest, and the rise of sensationism in France derived from Locke by Diderot and Voltaire, and more systematically by Condillac, would have very real consequences in the first nationally recognised schools for the blind and the deaf in France. The accidental discovery in 1786 by Valentin Haüy that embossed script could be read by the fingers, for example, implied in the words of Farrell that ‘sensitive fingers […] could take the place of insensitive eyes’ (1956: 93). The substitution of touch for sight, of hands for eyes, lay at the heart of the development of education for the blind. Or, in the words of Merry in an article appropriately titled ‘Fingers for eyes’, ‘There seems always to have been among civilized people at least a vague realization that the finger should serve as the eye of the blind’ (Merry 1937: 237).

In the Lettre, Diderot had questioned ‘a sensible blind man’ in order to ‘understand his psychology’ (1916a: 116–17), thereby subjecting him to philosophical speculations on the role of the sensorial in the elaboration of human knowledge. To be sure, sensibility was the foundation for any knowledge of the outside world and, as transpired through his interviews with blind subjects, Diderot was interested in exploring the way that sensibility also informed moral sentiment, theological questions, and even civic engagement. His recommendation of a tactile language for communication with the blind, deaf, and mute was considered not only a matter of universal ease for expression and understanding between individuals, but would also enhance the mental operations of these sensorily compromised subjects.