Examples of the Vilna gaon arguing with rishonim (according to qwerty that would make him a kofer ch”v)
Disagreement with the Rambam regarding Blessings (“Long or Short”): In his commentary to the Shulchan Aruch, the Gra rejects the Rambam’s interpretation of the Mishna regarding the length of certain blessings. While other Rishonim understood “long and short” as a technical, qualitative difference, the Rambam (in his commentary) took a different approach. The Gra argues that the Rambam in his code (Mishneh Torah) retracted his earlier view and that the phrase “to lengthen or to shorten” should be taken literally, and that the Rambam’s view was not in line with the Yerushalmi.
Correction of the Rambam on Niddah/Zavah: The Gra argued that the Rambam’s understanding of the alternating days for niddah and zavah was incorrect and did not follow the proper talmudic, leading to the Chatam Sofer noting that in some issues, the Rambam’s view was considered “rejected”.
Rejection of the Rashba on Prayer: Regarding changes to the wording of blessings, the Gra rejects the lenient view of the Rashba, which allowed for significant changes to the established wording of blessings.
Argument regarding the Third Meal on Yom Tov: The Rif and Rambam rule that a third meal is required on Yom Tov, just as on Shabbat. The Rosh disagrees. The Gra, in his commentary, sides against the Rif and Rambam, bringing support from the Yerushalmi that a third meal was not eaten on Yom Tov, even in Temple times.
Opposition to the Rambam regarding Tombstones: The Rambam (Laws of Mourning 4:4) argues that a tombstone should not be placed on the grave of a righteous person, as “their words are their memory.” The Gra’s approach, as later interpreted by others, stands in contrast to this, with some, like R’ Moshe Feinstein, arguing that the Rambam actually implies it is forbidden to place a tombstone, which is a position the Gra, in his practical application, did not follow.
Needless to say I accept chazal that Adam Harishon had relations with every animal (seems like you’re the kofer)
