I9 o 5 .] LAMBERT— THE STRAIGHT LINE CONCEPT. 89 



geometry, it is not an intuitive property of the straight line and it 

 cannot be proved by experiment. The continuity of the straight 

 line can be established only by means of axioms, whether these 

 axioms take the form given by Dedekind in his Essays on Number 

 or by Hilbert in his Foundations of Geometry. When the contin- 

 uity of the straight line has been established the Cartesian geometry 

 at once follows. 



Lehigh University, 

 April S, 1905. 



