The bridge between practical and deductive geometry: developing the ‘geometrical eye’

The dual nature of geometry, as a theoretical domain and an area of practical experience, presents mathematics teachers with the opportunity to link theory with the everyday knowledge of their pupils. Very often, however, learners find the dual nature of geometry a chasm that is very difficult to bridge. With research continuing to focus on understanding the nature of this problem, with a view to developing better pedagogical techniques, this paper reports an analysis of innovative geometry teaching methods that were developed in the early part of the 20th Century, a time when significant efforts were being made to improve the teaching and learning of geometry. The analysis suggests that the notion of the geometrical eye, the ability to see geometrical properties detach themselves from a figure, might be a potent tool for building effectively on geometrical intuition.