ABSTRACT
Definition 3. An ‘a¢ ne plane’ is a triple (P ;L; I), of sets of ‘points P,’ ‘lines L,’ and ‘incidence I P L,’ with the following properties: (1) Given two distinct points P and Q; there is a unique line `
incident with P and Q, and which we shall denote by PQ. (2) Given a line ` and a point P not incident with `, there is a
unique line m that is not incident with any points (is ‘disjoint from’) with ` and is incident with P . The line m is said to be ‘parallel’to `. (3) There are at least four points no three of which are ‘collinear’
(are not incident with a common line).
