 Adrien-Marie Legendre was a mathematician sympathetic to the didactic aims of the Elements but not to its original formulations. He wrote several different versions of his Éléments de géométrie (1794) with a view to restoring "Euclidean rigour" in the teaching of geometry, which in his view had been corroded by texts, such as one by Clairaut (1741), that relied on notions of self-evidence. They differ largely, as he had to admit, in their unsuccessful attempts to deduce the parallel postulate.