 A different kind of putative counterexample to  Minimality  involves perfectly natural properties which are “rigid” in the sense that whatever instantiates or fails to instantiate them does so necessarily. If  TSB  is true and \(F\) is rigid,  TSB  remains true when ‘perfectly natural property’ is replaced by ‘perfectly natural property distinct from \(F\)’. For example, if one held that every electron is necessarily an electron (if it exists) and that every non-electron is necessarily not an electron (if it exists), minimality would rule out claiming that being an electron is perfectly natural. Eddon  (2013)  argues that certain rigid relations among properties are perfectly natural, and thus make trouble for minimality: one of her examples is the three-place being the sum of relation that holds, for example, between the determinate mass properties being exactly 5kg in mass, being exactly 7kg in mass, and being exactly 12kg in mass.