[98] And besides what has been already advanced, this also may be asserted that three is the number of a plane figure, since a point has been laid down to be, according to a unit, and a line according to the number two, and a plane superficies according to to the number three. Also, four is the number of a cube, by the addition of one to the number of a plane superficies, depth being added to the superficies. From which it is plain that the essence of the number seven is the foundation of geometry and trigonometry; and in a word, of all incorporeal and corporeal substances.