The Ontological Argument is a highly sophisticated philosophical argument for the existence of God that is often poorly understood by believers and universally dismissed or even ridiculed by atheists, who usually do not properly grasp the argument either. In his anti-religious pamphlet "The God Delusion" Richard Dawkins made a complete fool of himself with the embarassing remark that the defendants of the Ontological Argument even "felt the need to resort to Modal Logic", which showed that he was completely ignorant of the fact that this argument simply is an exercise in modal logic (see this Q&A by William Lane Craig). The atheist philosopher Bertrand Russell once mocked the Ontological Argument as nothing but "a case of bad grammar". We will get back to him at the end of this post.
If you do not like to read lengthy blog posts like this, you find an excellent introduction to the modern modal version of the Ontological Argument in these two short YouTube videos:
History of the argument:
The original version of the Ontological Argument was formulated in 1011 by the medieval philosopher and theologian Anselm of Canterbury, based on his "perfect being theology", which defines God as a maximally great being ("that which no greater can be conceived"). Anselm postulated "existence" as a great-making property, which led to the refutation of his argument by the famous German philosopher Kant, who recognized that "existence" is not a perfection and actually not even a characteristic that adds anything to the exhausting description of an object or being.
Surprisingly, the Ontological Argument was resurrected in the 20th century by the philosophers Charles Hartshorne and especially Alvin Plantinga from the University of Notre Dame, based on the possible world semantics of modal logic (= the philosophy or logic of the possible and the necessary). Hartshorne and Plantinga happily acknowledged that mere "existence" indeed is not a valid great-making property or perfection, but they discovered and established that "necessary existence" definitely is such a property.
Premise 1: A maximally great being must have the great making property of necessary existence.
Therefore, the only chance for the atheist is to deny premise 4 (premise B in the simplified version), which means that he has to deny that God (a maximally great being) is possible. The atheist has to claim that God is logically impossible, because the concept of a maximally great being is incoherent or self-contradictory, like a "round square" for example.
Since the argument is logically valid and the premises are all rather true than false, the Ontological Argument is sound.
To avoid a common misunderstanding (e.g., by the skeptical philosopher David Hume; see here) it must be emphasized that the Ontological Argument does not try to prove the existence of God, but "only" shows that if his existence is possible than he must exist. Not too bad for a mere exercise in modal logic.
The earliest such objection was already made by the monk Gaunilo, a contemporary of Anselm. It represents a parody of the Ontological Argument, using an analogous argument to prove the existence of a "perfect island", as alleged reductio ad absurdum. Even though such parodies are still popular as objection among modern atheists, they are invalid arguments that involve incoherent concepts of "greatest beings", and completely ignore the crucial distinction between contingent and necessary beings, as well as the set of essential properties of a maximally great being (see here and here).
Many of the alleged "refutations" that you can find on YouTube or in the bestselling books of the New Atheists, are just nonsense arguments by village atheists and armchair philosophers that would never make it into a peer-reviewed journal for serious philosophy. The fact that such poor counter arguments have even been championed by distinguished scientists only shows that everything that scientists say outside their field of expertise should be taken with a grain of salt (of course this also applies to myself).
A perfect example is Douglas Gasking's absurd claim (quoted and supported by Richard Dawkins in "The God Delusion") that the Ontological Argument actually proves God's non-existence, because he would be a more formidable creator if he could create everything without even existing himself. It goes without saying that this is of course totally incoherent nonsense (see here).
A refutation of Dawkins' critique of the Ontological Argument by William Lane Craig, debating the empty chair of Richard Dawkins, who cowardly refuses any invitation to challenge him personally.
Likewise, naive attempts to "demonstrate" the alleged self-contradictory nature of great-making properties like omnipotence (e.g., "Can God create stone, which is so heavy that he cannot lift it?") fail miserably. No great-making property includes the capability to do the logically impossible. Even a maximally great and omnipotent God cannot create a married bachelor or make 2+2=5 true.
However, there is one remaining possibility, with which I actually sympathize, to get around the Ontological Argument. "Unfortunately" it is only open to a believer in classical theism, but not to atheists:
Last but not least, I would like to briefly address two objections that have been raised against a necessarily existing creator in the context of Leibniz's Cosmological Argument, but which are also relevant here:
- Can a necessarily existing creator be the ultimate explanation for a contingent world?
- Wouldn't a necessarily existing, omnipotent, omniscient, and omnibenevolent Creator necessarily have to create the best of all possible worlds?
Based on his very strict version of the Principle of Sufficient Reason, Leibniz indeed believed that God had to create our world, which is the necessarily existing best of all possible worlds. This of course invited ridicule, because our world obviously is contingent and not the best possible world.
The first question raises the issue, if a necessary cause always implies a necessary effect. This would lead to Leibniz's necessitarianism, in which the existing world exists necessarily and could not have been otherwise. However, there is an obvious exception, which allows for a contingent effect to have a necessary cause: If the necessary cause would be a necessarily existing person, who is endowed with freedom of the will, which is what most theists believe anyway, than such a necessary being could be the creator of a contingent universe.
The second question is also easily answered, because even God cannot create a logically impossible world. However, a "best of all possible worlds" is logically impossible, because there simply is no best possible world. We can always imagine a world, which is better (e.g., in which one more person is saved). Therefore, God had only the choice to not create at all, or to create a contingent world like ours, which is very good, but not maximally good.
To sum up:
The Ontological Argument is either a valid and sound argument for the existence of God, or God exists necessarily as unmoved mover. All atheist critiques and alleged refutations do either not apply to the modern modal version of the argument, or are just "cases of bad grammar". Check mate Bertrand Russell, RIP!