Number, place, and combination . . . the three intersecting but distinct spheres of thought to which all mathematical ideas admit of being referred. — James Joseph Sylvester Copy Share Image
A modern theory of knowledge which takes account of the relational as distinct from the merely relative character of all historical knowledge… — Karl Mannheim Copy Share Image
“To interpret dots in the sky as white-hot, million-kilometre spheres, one must first have thought of the idea of such spheres. And… — David Deutsch Copy Share Image
