Which later philosophers accepted versions of St. Anselm of Canterbury’s ontological argument?

St. Anselm of Canterbury’s ontological argument, which posits that the existence of God is implied by the very concept of a being "than which nothing greater can be conceived," has been a subject of significant philosophical debate since its formulation in the Proslogion.123

While the argument faced early criticism from Anselm’s contemporary Gaunilo of Marmoutier, it was later accepted in various forms by several prominent philosophers, most notably:

• René Descartes: In his Meditations (1641), Descartes reformulated the argument, making explicit the assumption that existence is a perfection or attribute that a perfect being cannot lack.243
• Benedict de Spinoza: He also accepted the argument in a modified form.2

In the 20th century, the argument saw a resurgence among several Christian philosophers, including Charles Hartshorne, Norman Malcolm, and Alvin Plantinga. These thinkers asserted the validity of a version of the argument based on "necessary existence," suggesting that a being that necessarily exists cannot coherently be thought not to exist.3

Conversely, the argument has been famously rejected by others, such as Immanuel Kant, who argued that existence is not a predicate.23