In a well-known quotation from Speusippus in the Theologumena Arithmeticae (82.10 de Falco), said to have been derived from Pythagorean sources, especially Philolaus, occur the following sentences: And again a little later: Similarly Sextus Empiricus (Math. 10. 279–80), drawing evidently on a relatively early Pythagorean source, writes as follows: And Aristotle himself writes of the Pythagoreans (Met. 1036b12): There were, in fact, certain Pythagoreans who equated the number 2 with the line because they regarded the line as ‘length without breadth extended between two points’; and likewise the number 3 was equated with the plane and 4 with the solid.