ipse dixit

noun | \ ˈip-sē-ˈdik-sət \ | ip·se dix·it

1. : an assertion made but not proved According to the city, it is “self-evident” that killing animals for food is “important”; the eradication of insects and pests is “obviously justified”; and the euthanasia of excess animals “makes sense.”… These ipse dixits do not explain why religion alone must bear the burden of these ordinances —Church of the Lukumi Babalu Aye v. City of Hialeah, 508 U.S. 520 (1993)