Raison d’être (rey-zohn-de-truh)

(noun) Main reason or justification for existence

Examples:

1. June asserted that the multi-cultural club must have an open-door policy because inclusivity was its raison d’être.
2.  June astutely pointed out that openness to new ideas and foreign people has historically been Americas raison d’être, and that those calling for the values of our founders should readily welcome refugees and immigrants.