The relevance of Kant’s objection to Anselm’s ontological argument

The most famous objection to the ontological argument is given in Kant’s dictum that existence is not a real predicate. But it is not obvious how this slogan is supposed to relate to the ontological argument. Some, most notably Alvin Plantinga, have even judged Kant’s dictum to be totally irrelevant to Anselm’s version of the ontological argument. In this paper I argue, against Plantinga and others, that Kant’s claim is indeed relevant to Anselm’s argument, in the straightforward sense that if the claim is true, then Anselm’s argument is unsound. Very famously, St Anselm (1078/1903, 8) said: ... if that, than which nothing greater can be conceived, exists in the understanding alone, the very being, than which nothing greater can be conceived, is one, than which a greater can be conceived. But obviously this is impossible. Hence there is no doubt that there exists a being, than which nothing greater can be conceived, and it exists both in the understanding and in reality. Kant said some equally famous things on the topic. Most celebrated is his remark that: ‘Being’ is obviously not a real predicate; that is, it is not a concept of something which could be added to the concept of a thing. ... . By whatever and however many predicates we may think a thing ... we do not make the least addition to the thing when we further declare that the thing is. (Kant (1781/1929), A598/B626–A600/B628.) What does what Kant said have to do what Anselm said? Is it even relevant? Several writers claim that it is not. They contend that Kant’s claim that existence is not a real predicate [henceforth, Kant’s dictum], the most famous objection to Religious Studies (2011) 47, 345–357 f Cambridge University Press 2010 doi:10.1017/S0034412510000314