  (iii) Concerning the Weak Principle there has been an interesting development of a line of argument due to Black (1952) and Ayer (1954) in which it is proposed that there could be exact symmetry in the universe. In Black’s example it is suggested that there could be a universe containing nothing but two exactly resembling spheres. In such a completely symmetrical universe the two spheres would be indiscernible. Against this has been noted, e.g., Hacking (1975), that such a completely symmetrical situation of two spheres could be re-interpreted as one sphere in a non-Euclidean space. So what might be described as a journey from one sphere to a qualitatively identical one 2 units apart could be redescribed as a journey around space back to the very same sphere. Quite generally it might be said that we may always redescribe apparent counter-examples to the Weak Principle so that qualitatively identical objects symmetrically situated are interpreted as the very same object. This Identity Defence, as Hawley (2009) calls it, is vulnerable to a version Adam’s continuity argument. (1979)