If this man had used his reason as much as his memory in a matter where reason alone ought to be employed, or if he had had as much respect and love for truth as he had veneration for the author upon whom he commented, it is likely that having spent so much time on such a small subject, he would have agreed that the definitions Euclid gives of a plane angle and parallel lines are defective, that they do not sufficiently explain their nature, and that the second proposition is absurd, since it cannot be proved except by using the third postulate, which one ought not to accept as quickly as one does the second proposition, since by agreeing with the third postulate, which is that from any point a circle can be described of whatever diameter one wishes, one not only agrees that one can draw a line equal to another line from a single point (which Euclid accomplished in a very roundabout manner in this second proposition) but one also agrees that one can draw infinitely many lines of whatever length from any point.