The text of Rule 702 did not make admissibility of expert testimony depend on general acceptance, and there was no evidence that Congress intended to incorporate a general acceptance standard into Rule 702. "Given the Rules' permissive backdrop and their inclusion of a specific rule on expert testimony that does not mention 'general acceptance,' the assertion that the Rules somehow assimilated "Frye" is unconvincing. "Frye" made 'general acceptance' the exclusive test for admitting expert testimony. That austere standard, absent from, and incompatible with, the Federal Rules of Evidence, should not be applied in federal trials."