## A quotation by Adriaan van Roomen

Surely there is a certain science common to arithmetic and geometry to which properties common to all quantities pertain: since a proportion is common to all quantities, not only abstract ones such as numbers and magnitudes, but also concrete ones such as times, sounds, voices, places, motions, and forces (for all these and many others are said to have a proportion if their relation is considered from the viewpoint of quantity).