 There is a striking resemblance between Whitehead’s construction of points and the construction of real numbers by Georg Cantor, who had been one of Whitehead and Russell’s main sources of inspiration next to Peano. Indeed, Whitehead defined points as equivalence classes of converging series of volumes, and Cantor defined real numbers as equivalence classes of converging series of rational numbers. Moreover, because Whitehead’s basic geometrical entities of geometry are not (as in Euclid) extensionless points but volumes, Whitehead can be seen as one of the fathers of point-free geometry; and because Whitehead’s basic geometrical relation is the mereological (or part-whole) relation of extension, he can also be seen as one of the founders of mereology (and even, when we take into account his later work on this topic in part IV of Process and Reality, of mereotopology).