Ipse dixit is a Latin phrase that translates to “he said it himself.” Ipse dixit means a person’s own assertion without relying on any authority or proof. It usually implies an assertion of authority, as in a statement is true based on the speaker’s authority and nothing else. In legal context the term is usually used to criticize arguments based solely upon authority and not backed by any proof.
For an example of usage, “An expert's simple ipse dixit is insufficient to establish a matter; rather, the expert must explain the basis of his statement to link his conclusions to the facts.” Earle v. Ratliff, 998 S.W.2d 882, 890 (Tex. 1999).
[Last updated in June of 2020 by the Wex Definitions Team]