Now if I take the subject (God) with all its predicates (omnipotence being one), and say, God is, or There is a God, I add no new predicate to the conception of God, I merely posit or affirm the existence of the subject with all its predicates - I posit the object in relation to my conception.
Accordingly, what goes wrong with the ontological argument is that the notion of existence is being treated as the wrong logical type.
Thus, if God exists only as an idea in the mind, then we can imagine something that is greater than God (i.e., a greatest possible being that does exist).
But we cannot imagine something that is greater than God (for it is a contradiction to suppose that we can imagine a being greater than the greatest possible being that can be imagined.) Therefore, God exists.
To be a little bit clearer, existence is not a property (in, say, the way that being red is a property of an apple).
Essays In Goan History - Ontological Argument Anselm Essay
Rather it is a precondition for the instantiation of properties in the following sense: it is not possible for a non-existent thing to instantiate any properties because there is nothing to which, so to speak, a property can stick. To say that x instantiates a property P is hence to presuppose that x exists.But suppose that he went on to say, as if by a logical inference: "You can no longer doubt that this island which is more excellent than all lands exists somewhere, since you have no doubt that it is in your understanding.And since it is more excellent not to be in the understanding alone, but to exist both in the understanding and in reality, for this reason it must exist.His argument is not easy to understand especially if you have had little philosophical training, but don't despair, if you re-read his argument a couple of times you will probably get his idea.According to Kant, Anselm’s mistake is to treat existence as if it is a further property we might conceive of something possessing, in addition to various other properties such as, for example, being tall or all-powerful. Kant rejects premise 3 ["A being that exists as an idea in the mind and in reality is, other things being equal, greater than a being that exists only as an idea in the mind"] on the ground that, as a purely formal matter, existence does not function as a predicate.Concepts, as a logical matter, are defined entirely in terms of logical predicates.Since existence isn't a logical predicate, it doesn't belong to the concept of God; it rather affirms that the existence of something that satisfies the predicates defining the concept of God.This argument was once very popular, but its popularity has waned.Few philosophers – and I include among them the majority of philosophers who believe in theism– now consider the argument cogent.On the seemingly safe assumption that there is no such island, it seems we have no choice but to accept that there is something wrong with this argument, including Anselm's similarly constructed argument.The philosopher Immanuel Kant offers yet another well known criticisms of the ontological argument.