Full Idea
Originally, the focus of geometry was space - matter and extension - and the subject matter of arithmetic was quantity. Geometry concerned the continuous, whereas arithmetic concerned the discrete. Mathematics left these roots in the nineteenth century.
Gist of Idea
Mathematics originally concerned the continuous (geometry) and the discrete (arithmetic)
Source
Stewart Shapiro (Philosophy of Mathematics [1997], Intro)
Book Reference
Shapiro,Stewart: 'Philosophy of Mathematics:structure and ontology' [OUP 1997], p.13
A Reaction
Mathematicians can do what they like, but I don't think philosophers of mathematics should lose sight of these two roots. It would be odd if the true nature of mathematics had nothing whatever to do with its origin.