How does the idea of necessary existence appear in later versions of St. Anselm of Canterbury’s argument?

In later philosophical discourse, the concept of "necessary existence" has been used to refine and defend the ontological argument originally formulated by St. Anselm of Canterbury.12

In the 20th century, philosophers such as Charles Hartshorne, Norman Malcolm, and Alvin Plantinga proposed a version of the argument hinging on the idea that necessary existence is a property of higher value than mere existence. They argued that a being possessing necessary existence cannot coherently be thought not to exist; therefore, God, as the unsurpassably perfect being, must possess this attribute and thus exist.1

However, this approach has faced significant criticism. Critics argue that it fails to distinguish between logical and ontological necessity. While logical necessity concerns the relations between concepts, it cannot determine whether a concept is actually instantiated in reality. Consequently, opponents maintain that even if one defines God as an ontologically necessary being—existing as an ultimate fact without dependence on anything else—this does not prove that such a being actually exists, as the question of instantiation remains a matter of fact that cannot be determined a priori.1