The ontological argument: Anselm's two forms, Descartes's version, the a priori method, and the criticisms of Gaunilo and Kant that existence is not a predicate.

What this dot point is asking

You need to explain the ontological argument for God's existence: Anselm's two forms, Descartes's version, the a priori method, and then evaluate the criticisms of Gaunilo (the perfect island) and Kant (that existence is not a predicate). This is a key theme of A2 8, and it is unique among the arguments for God because it is a priori: it tries to prove God from the concept of God alone, without appeal to experience.

Anselm's first form

Anselm's second form

Descartes's version

The criticisms: Gaunilo and Kant

The two classic objections target different aspects of the argument.

• Gaunilo's perfect island. Anselm's contemporary Gaunilo parodied the argument: by the same reasoning, the most perfect conceivable island must exist, since an existing island would be greater than an imaginary one, which is absurd. Anselm replied that the argument works only for God, the necessary being, not for contingent things like islands.
• Kant: existence is not a predicate. Kant gave the most influential objection: existence is not a predicate (a property that adds something to the concept of a thing). Saying a thing exists does not add to its concept, as a real and an imagined coin share the same concept; so bundling "existence" into the definition of God cannot prove that God exists.

Strengths and weaknesses

A model evaluation paragraph might run: "The ontological argument is remarkable for its a priori ambition, attempting to show that, once we grasp what God is, we see that God must exist, and its second, modal form is genuinely resistant to easy dismissal, since necessary existence does seem different in kind from the contingent existence of islands, which is why Malcolm and Plantinga have revived it. Yet the criticisms are weighty. Gaunilo's parody exposes the worry that the argument could conjure any perfect thing into existence, and although Anselm's reply that God alone exists necessarily blunts it, the deeper problem is Kant's: if existence is not a predicate, then no amount of analysing the concept of God can establish that the concept is instantiated, since existence adds nothing to a concept. The judgement, therefore, is that Kant's objection defeats the first form of the argument, and that while the modal second form remains philosophically interesting and contested, the ontological argument fails as a conclusive proof of God's existence."

Try this

Q1. What does it mean to call the ontological argument "a priori"? [2 marks]

• Cue. It is known independently of experience, proving God from the concept of God alone, not from observation of the world.

Q2. Explain Gaunilo's "perfect island" criticism of the ontological argument. [6 marks]

• Cue. The same reasoning would prove the most perfect island must exist, which is absurd; Anselm replied that the argument works only for God, a necessary being, not for contingent things.

Q3. "Existence is not a predicate, so the ontological argument fails." Discuss. [20 marks]

• Cue. Explain Kant's objection, apply it to the first form, then weigh the reply that necessary existence (the second, modal form) may be a genuine property. Reach a judgement.