Activities involving form had a key role in Édouard Séguin's approach to the education of “idiots” or “feeble minded” people, in his pioneer work developed between 1837 and 1847. We discuss the geometrical content of exercises on lines, configuration, solids, and the plane, which were intended to awake the child's awareness in relation to the environment. The failure of their attempts, conducted together with the medical doctor Jean Itard, to teach a single pupil how to draw a square was the starting point of theoretical and experimental work linked to his earlier reflections on art (painting). Séguin was able to develop intuitive, implicit geometrical knowledge that schools did not usually teach, which was revealed as crucial for encouraging disabled children's activity, intelligence, and will. His vision is still present in Montessori's educational materials and offers an example of attention to geometry in basic education among the innovators in the 19th century.
Millan gasca, A., Gil Clemente, E. (2021). Geometry as ‘Forceps of Intelligence’: Lines, Figures, and the Plane in Édouard Séguin’s Educational Thought. BOLLETTINO DI STORIA DELLE SCIENZE MATEMATICHE, 41(2), 315-339 [10.19272/202109202005].