Gaunilon de Marmoutiers
With Anselm's reasoning, one could prove that a perfect island exists.
Life
Benedictine monk of the abbey of Marmoutier, near Tours, in the 11th century. Soon after Anselm's Proslogion (c. 1078) he wrote 'On Behalf of the Fool' to show that the ontological argument would prove too much: with the same reasoning one could demonstrate that a perfect 'lost island' exists. Anselm took the reply seriously enough to have it copied with his own book.
Main works
An objection to Anselm's ontological argument, with the lost-island example.
In his own words
« They say that somewhere in the ocean there is an island which some call the lost island, because of the difficulty, or rather the impossibility, of finding what does not exist. »
Aiunt quidam alicubi Oceani esse insulam, quam ex difficultate vel potius impossibilitate inveniendi quod non est, cognominant aliqui perditam
« Either I should believe that he was jesting, or I know not which I ought to regard as the greater fool. »
aut jocari ipsum credam, aut nescio quem stultiorem debeam reputare
Positions
click a row to see the evidenceA monk and believer, he does not doubt God: he only denies that Anselm's argument proves it.
Gaunilo, Pro insipiente (c. 1070)