The evidence of his cleverness was of the higher intuitive order, lying in his lady-patients’ immovable conviction, and was unassailable by any objection except that their intuitions were opposed by others equally strong; each lady who saw medical truth in Wrench and "the strengthening treatment" regarding Toller and "the lowering system" as medical perdition.
There are no more uses of "unassailable" in the book.
Show samples from other sources
But worst of all for Helene, the vultures build their nests above the clouds, atop the most unassailable peaks.
Sabaa Tahir -- An Ember in the Ashes
Everyone had pitched in to help out, even the people she usually thought of as almost unassailable in their reserve: Kadir, Jia, Maryse.