 One prominent way of resisting this argument is to reduce it to absurdity by appeal to “parity of reasoning”. Johannes Caterus, for instance, objected to Descartes that by a precisely parallel form of reasoning we could prove the real existence of the object of an idea of an existent lion (AT 7.99). Gaunilo’s reply to Anselm centuries earlier was similar: by parity of reasoning, one can prove the existence in reality (and not just in the understanding) of the maximally perfect island (Anselm 102).