 The philosopher P.T. Geach first broached the subject of relative identity and introduced the phrase ‘relative identity’. Over the years, Geach suggested specific instances of RI (a variant of the case of Oscar and his tail is due to Geach (1980)) and in this way he contributed to the development of the weak view concerning relative identity, i.e., the view that while ordinary identity relations are often relative, some are not. But Geach maintains that absolute identity does not exist. What is his argument?