The fusion of plane and solid geometry in the teaching of geometry: Textbooks, aims, discussions
The idea of the fusion of plane and solid geometry originated from projective and descriptive geometry, which worked with projections in space and sections. Different authors of textbooks (starting from Bretschneider in 1844 to Méray in 1874/1903; de Paolis in 1884; Lazzeri & Bassani in 1891, also translated into German by Treutlein in 1911) adopted this idea, mixing plane and solid considerations. For instance, the chapter on the properties of incidence also referred to the mutual position of a plane and a straight line, while homothety was defined in space and then on the plane.