This is based on research that has discovered crucial, hitherto unknown biographical information. First, I review the theories of authors who helped to generate the whole 'affair' of Durkheim's two pre-names, most often in seeing it as a way to interrogate his relation with Judaism. Next, I discuss how the issue comes with elements that are incomplete or inexact. It is then to present new evidence of Durkheim's ambivalence and changing attitude towards his first, identifiably Jewish pre-name. The census records during his time at Bordeaux show that he registered himself as 'David' in 1891 and 1896, but abandoned this and switched to 'Émile' in 1901. Accordingly, I examine possible interpretations of the change, in terms of the political context of the Dreyfus Affair, events in his family life, his institutional position, his growing reputation, and a programme of research in which he resolved on a scientific treatment of religion.