Explain the Ontological argument.

The ontological argument, in whichever version, has been the object of a great deal of philosophical criticism. Traditionally, the objection posed by the 18th-century philosopher Immanuel Kant has been thought to be one of the most decisive. Kant argued that the problem with the argument lay in its claim that existence is a predicate. (A predicate term describes something done by a subject; so, in the sentence "John is eating" the predicate "is eating" describes something that the subject, John, is doing.) Kant argued that existence cannot be a predicate because it does not add any new information to an understanding of the subject. To be told that John is bald, that he is eating, and that he is angry is to add three things to the stock of information about him. However, to be told that he exists does not genuinely communicate something about him. Likewise with God. To state simply that God's existence follows from thinking about him is to have said nothing other than that God exists. Kant argued that nothing of philosophical consequence has been learnt. It is for this reason that many modern-day philosophers have held the ontological argument to be in error.

The other main proofs offered, the cosmological argument and the argument from design, are related. Both are a posteriori arguments, that is, concerned with the objects of experience. Unlike the ontological argument, the cosmological argument always holds what is known as an existential premise; part of the argument asserts that something exists. It then seeks to make clear the view that the reason why there is something rather than nothing is down to the fact that the something in question was caused to come about. The origin of this something, or its first cause, is more often than not claimed to be God. The cosmological argument has enjoyed great appeal among philosophers of widely differing religious traditions. It has been advanced by, for example, the ancient Greeks Plato and Aristotle, the Islamic philosophers Avicenna and members of the Kalam school, the Jewish theorists Maimonides and Spinoza, and Christian philosophers of many denominations such as Aquinas, John Locke, and Leibniz. Despite its broad appeal and historical popularity, the cosmological argument has been subject to much criticism. For example, it is thought that the argument's appeal to the notion of a first cause is problematic or that it arbitrarily demands an explanation for everything, where such a request is considered to be unwarranted. In recent times, philosophers such as William Lane Craig and Richard Swinburne have attempted to exempt the cosmological argument from such criticisms.