In Proslogion, Anselm claims that understanding God as “something beyond which a greater nothing can be thought” refers to God’s existence in the mind and facilitates our understanding of God existing also in reality. The argument is epistemological and not ontological since its conclusion is our understanding of God’s existence, not a proof or demonstration that God exists. However, I argue that Anselm’s notion of existence in the mind invokes mentalism, a claim that meaning is housed in the mind and (...) semantic rules are contained within linguistic expression itself. Wittgenstein argued that mentalism is a mistaken conflation of linguistic understanding with ostensive reference to one’s private sensations. Instead, all linguistic understanding depends on the public use of rules operating within a specific semantic context. If mentalism is false, then the concept of existence in the mind alone is a shallow metaphysical idea, rendering the rest of the argument invalid. (shrink)