Descartes ontological and Empiricist responses to a priori arguments for existence, and Kant-existence not a predicate

How does Descartes define God

A supremely perfect being

What is Descartes ontological argument

P1. I have the idea of God

P2. the idea of god is the idea of a supremely perfect being

P3. a supremely perfect being does not lack any perfection

P4. existence is a perfection

C. therefore, God exists

What does Descartes think God's existence is

necessary, because 'God' entails that God exists, so he must exist. Existence is a predicate

What is the only strength of Descartes argument

It is deductively valid

How does Hume respond to Descartes ontological argument

Hume's fork. you can't prove the existence of something through a priori reason unless the opposite entails a contradiction. So, God doesn't necessarily exist

How does Ayer respond to Descartes ontological

a priori propositions are certain because they are tautologies. you cannot prove God from a tautology because God's existence is not a tautology

Kant's objection that existence is not a predicate

A predicate must add to our understanding of the concept. 'God exists' does not add a predicate to our understanding because it just says 'God is'.

He says "Existence is obviously not a real predicate"