Friday 6 April 2012

The Ontological Argument for the Existence of God

The ontological argument is widely thought to have been first clearly articulated by St. Anselm of Canterbury, who defined God as the greatest conceivable being. Anselm’s reasoning was that, if a being existed only in the mind but not in reality, then a greater being was conceivable (a being which exists both in the mind and in reality). The famed seventeenth-century French philosopher René Descartes utilised the ontological argument. The ontological argument was revived by Norman Malcolm in 1960. Variants of the ontological argument have been supported and defended by contemporary philosophers such as Alvin Plantinga (who bases his argument on modal logic) and William Lane Craig.

The ontological argument was first criticised by Gaunilo of Marmoutiers, a contemporary of Anselm of Canterbury. He argued that the ontological argument could be used to demonstrate the existence of anything, utilising an analogy of a perfect island. The argument was also criticised by the famed Catholic philosopher Thomas Aquinas and also by David Hume and Immanuel Kant.

The Ontological Argument: Possible Worlds

To properly understand the ontological argument, it is necessary to specify what philosophers mean when they talk about “possible worlds.” A “possible world” refers to a counterfactual – a state of affairs that could have been true. For something to exist in a “possible world” simply means that its existence is logically possible.

The ontological argument for the existence of God refers to the claim that the very logical possibility of God’s existence entails his actuality. The ontological argument begins with the claim that God, by definition, is infinitely great. Thus, no entity can surpass God’s greatness. God, in other words, is the greatest conceivable being (if one could conceive of a greater being, then that would be God). Being infinitely great entails existence in every possible world since a being that existed in merely some possible worlds would be superseded in greatness by a being that existed in every possible world. Moreover, a maximally great being is one that possesses the property of necessary existence. Thus, if a being of maximal greatness exists in some possible world, then it exists in every possible world. If an infinitely great being exists in every possible world then that being must exist in the actual world. Since God is an infinitely great being, therefore, God must exist.

The Ontological Argument: The Premises

The conclusion of the ontological argument, as formulated by Alvin Plantinga and others, depends on a form of modal axiom S5 (which contends that if the truth of a proposition is possible, then it is possible in all worlds). This axiom also contends that, if it is possible that a proposition is necessarily true (that is to say, it is necessarily true in some possible world), then it is necessarily true in all possible worlds.

The logic of the ontological argument is formally summarised by philosopher Alvin Plantinga as follows:

1. A being has maximal excellence in a given possible world W if and only if it is omnipotent, omniscient and wholly good in W; and

2. A being has maximal greatness if it has maximal excellence in every possible world.

3. It is possible that there is a being that has maximal greatness. (Premise)

4. Therefore, possibly, it is necessarily true that an omniscient, omnipotent, and perfectly good being exists.

5. Therefore, (by axiom S5) it is necessarily true that an omniscient, omnipotent and perfectly good being exists.

6. Therefore, an omniscient, omnipotent and perfectly good being exists.

The Ontological Argument: Is It Sound?

While the ontological argument has been the subject of fierce criticism by many contemporary philosophers, many of the criticisms of it result from a failure to properly understand the argument.

The ontological argument is clearly logically valid – that is to say, the conclusion necessarily follows provided that Premises 1 to 5 are true. The crucial Premise, therefore, is Premise 3, namely, that it is possible that a maximally great being exists. To refute this Premise, one would need to show that the very concept of an infinitely great being is somehow logically incoherent – like a “married bachelor”. Since no argument to that effect has been forthcoming, however, it follows necessarily and inescapably that “Therefore, a maximally great being exists.”

This article was cross-posted from


  1. I would add that Robert Maydole's Modal Perfection Argument gives an argument in favor of Premise 3, that it is possible that a maximally great being exists.

  2. To refute this Premise, one would need to show that the very concept of an infinitely great being is somehow logically incoherent – like a “married bachelor”. Since no argument to that effect has been forthcoming, however, it follows necessarily and inescapably that “Therefore, a maximally great being exists.”

    I don't agree with this at all. It doesn't follow (much less follow necessarily) that because nobody has yet come up with an argument against premise 3 that premise 3 is therefore true. It could be false for some reason that nobody has yet thought of.

    Consider this premise instead:

    3': It is possible that there is no being that has maximal greatness.

    By your reasoning, unless somebody can show that 3' is logically incoherent, then necessarily, no such being exists.

    1. Thanks, Sam. Yes, that was poorly worded on my part. I didn't mean to imply that the premise was true because no arguments to the contrary had been forthcoming. I think there is good reason to believe Premise 3 to be correct, and will maybe post another article on that.

  3. I don't understand how you get from 4 to 5. If it is possible in 4, then how does that possibility result in a necessity in 5?

    1. I don't necessarily endorse this argument, Bobby, but premise 5 follows from the S5 axiom of modal logic. This axiom says that, if something is possibly necessarily true, then it is necessarily true. This can be seen most easily when put into the language of possible worlds: a maximally excellent being is defined, partly, as existing in all possible worlds (if it is possible, that is). To say that it possibly exists is to say that it exists in some possible world. But, if it exists in some possible world and if it is defined as something which would exist in all possible worlds, it follows that it exists in all possible worlds.

  4. One could be careful about 'possible' here. To see why, consider this:

    If God exists, god necessarily exists (G -> []G)
    It is possible that god does not exist (<>¬G)
    If it is possible god does not exist, then god does not necessarily exist. (<>¬G --> ¬[]G)
    God does not necessarily exist (¬[]G)
    God does not exist. (¬G)

    It is certainly epistemically possible (could be for all we know) that there is a maximally perfect being. But it is also possible (epistemic sense) for there not to being a maximally perfect being, and we can construct a reverse modal argument that goes from this possibility to God's non-existence. (Indeed, this reverse argument is stronger than the forward one, as it doesn't need S5).

    For either argument to work the possibility needed is metaphysical possibility - that in fact there are these possible worlds where God does/does not exist. The above shows that "it seems *possible* to me", or "no one has shown it necessarily false" is too lax a standard for affirming "God is metaphysically possible" (as "Possibly god doesn't exist" passes the same tests). Reasons are needed why "God is metaphysically possible" is more plausible than "God's nonexistence is metaphysically possible", and (pace Maydole), I don't see why reasons would be offered besides the standard repertoire of philosophy of religion. If so, then Ontological arguments get us nowhere.

  5. Perhaps you missed it but this one is a bit of a problem for you and also shines a large and shiny light on the old PoE issue for Theists in general.

    Premise 1 is self contradictory in many ways but here is an example straight from Wikipedia: "if God is omnipotent, then he should be able to create a being with free will; if he is omniscient, then he should know exactly what such a being will do (thus rendering them without free will)."

    So the being described in permise 1 can not exist according to the description given in premise 1.

    In fact this is often given as a logical proof of the non-existence of the particular type of god described in "premise" 1.

    PS so why is there so much evil/suffering in the world?

    1. You have ascribed to theists problems we don't actually have for holding our views to be rational. Can god make a stone so heavy he can't lift it type thing. This has been asked and answered. Free will is not negated by god's omniscience. Besides it's the buddies on your side of the great divide, Dawkins, etc. They're the ones who claim free will to be but an illusion.

      PS The problem of suffering is an appeal to our emotion, not our intellect. It could be the suffering we see is necessarily so in the best of all possible worlds. A world where beings are given the freedom to chose good over evil. Can I suggest you try some Alvin Plantinga. Your question deserves a serious reply. That's why you should seriously investigate the answers.

  6. So there are answers.

    But you aren't going to tell us what they are?



    I've read some Plantinga and wasn't aware he even claimed to have an answer to this.

    I spent money on a book by McDowell on a previous similar occasion to be later told they had recommended me the wrong book.

    Surely you can summarise the answer can't you?



  7. You have been provided with a possible answer. It may be that the suffering we see is necessarily so in the best of all possible worlds. There really are none so blind as those who will not see. Not liking the answer is not the same as not having been given one.

  8. Earthquakes are necessary for the best possible world?

    That is seriously what you are saying?

    Fair enough.

    I think that a wholly good, omniscient and omnipotent would be able to solve that problem easy-peasy. That's why I don't think one exists.

    If all this suffering is necessary for this best of all possible worlds then how would you react if someone came up with a way to stop them? Would this be going against gods plan.



    PS I'm not blind I am just persistant, and not as rude as you. :-)

  9. Be that as it may, there are sound rational arguments that have been made by some of the greatest philosophers and theologians who have ever lived. The problem of evil is not late breaking news. Augistine nailed this one and hit it hard. It is something theists have addressed in great depth throughout history. Your question comes across as the simple minded bumper sticker of someone unfamiliar with the current state of the debate. You are free to reject their arguments. Just think you should familiarize yourself with them first. And no it's not my responsibility to spoon feed you.

    So a guy told you to buy a book once and it didn't contain the number 42 you were looking for, and you don't like my brand of snark, eh? Oh well. I guess I am rude, sorry for that.

  10. OK our differences seem to boil down to the fact that you refuse to even drop a hint about what kind of answers might be out there in summary form is unreasonable and you are topping it off by being rude about me for even asking.

    I think it much more likely that you haven't a clue.

    I have in fact read around lots of these supposed answers and I think that there are major holes in all of them. In fact there is a consensus amongst philosophers that a satisfactory answer to the POE has yet to be found.

    I thought the point of this blog was discuss these issues. Not to refuse to and be rude to people who ask questions.

    This is not good christian behaviour.


  11. So you thought you where going to bushwhack the ignorant theists and it didn't go to plan. Therefor I'm not behaving myself? You make me laugh. This isn't my blog, my views and tone should not be attributed to anyone but me. I've only just discovered this blog myself. Have you ever witnessed the way atheists treat Christians on their own blog sites? I would say my tone and manner is rather tame by comparison.

    I'm not behaving as a good Christian should? Was it immoral behavior? If so what makes you as an admitted atheist think morality even exists, objectively speaking?

    That sword you are attempting to slash and burn with has two edges you know? I have dropped hints your way aka Plantinga, Augistine, "possible worlds" along with a suggestion to read more.

    Oh, so you are edumacated. But because I refuse to spend half my day writing a summary of the arguments given by some of the greatest philosophers and theologians who have ever lived. That must mean I'm unfamiliar with them?

    First you claim you have to have never seen a well thought out rational argument regarding the POE. Then you claim to be very familiar with them, but find them unconvincing. Which is it? Here is a summary of Augistine knocking this one out of the park. Augustine on Evil


    Don't say I didn't never give ya nothin.

    Sorry was that me being unchristian again? Why? Because I do not feel compelled to play by your rules? Heck you even feel entitled to declare me unchristian for not playing the game the way you, an atheist, wishes to play. Since when do atheist get to declare who is and who is not behaving in a Christian manner? On what authority do you base that claim? In fact on what do you base the claim that right and wrong even exists in any real sense?

    The evolutionary argument doesn't get us there. It may explain why we think right and wrong exists. It does not however give any foundation for thinking of right and wrong as anything more than the popular fashion of the day.

    I say right and wrong, good and evil exists. That what happened in Auschwitz was evil. That it was wrong is a brute fact. Just as much a fact as the trajectory of the planets in the solar system. That right and wrong are objectively true in and of themselves. That what happened in Auschwitz would be wrong even if there wasn't a single human being who thought as much.

    As an atheist you have no rational argument for a belief in the existence of right and wrong. In that light your claim to have been wronged by me seems a bit ironic, doesn't it?

    The current state of the debate has atheists on the back foot. Not theists when it comes to the POE. Despite what the "New Atheists" attempt to claim. Such as Dawkin's with his jejune philosophical insights. Theists have honestly tackled the question. There are a great many well reasoned and rational arguments for why evil may exist in the best of all possible worlds. You may claim to find them unconvincing if you wish. What you can no honestly do is claim a theist is being illogical or ignorant for finding them to be well reasoned and rational. When it comes to holes, my suggestion to you would be to stop digging once you find yourself in one.

    Sorry if my Christianity does not comport to your ideas on what my moral obligations should be, but then I'm not about to cede that right and wrong even exists for someone who has no intellectual foundation for the very existence of right and wrong.

    Thanks for playing with me just the same. Perhaps you can find someone more to your liking here. I hope you do. Good luck to ya.

    I think you need to substantiate the classical logical fallacy you have posited here. The one about most philosophers. You do know that even if true an appeal to authority is a logical fallacy that does not produce a convincing argument? A convincing argument is based on logic and reason.

  12. Hi Cam,

    I asked a question.

    I didn't set a trap.

    I haven't been rude or nasty. Don't blame me for you being rude to me because some other people were rude to some other people. Take some responsibility for your own words.

    You seem to feel you can be rude and nasty just because I am an atheist which is pretty good evidence that you have a weak grasp of morals.

    Your link addresses the existence of Evil. I'm asking about suffering.

    Read my question. How does a perfectly good, all knowing and all capable god end up with children being slowly killed in earthquakes.

    You seem intent on mocking education too.

    I did write about being good without god previously here:

    Which, by the way, has a very friendly chat with some religious folks in the comments.

    I'm not going to repsond to the rest of your bile.

    I would still appreciate a polite discussion with anyone else about my question.



  13. Tsk tsk my bile? It's not bile, it's just my honest and uncut opinion. Yes, well... I'm not the pacifist Christian of the hippie day dreams of yesteryear either. Have been told this before and if I'm not your cup of tea that's alright with me. My intent was not to offend, but to challenge. You say you're familiar with the arguments that have been made. I see no evidence of this though.

    Honestly, you're looking for an answer to the POE on a relatively obscure Christian blog site's comments section?

    No you're not?

    You are here daring Christians to come sit your parlor. A parlor where you've mistakenly thought the high brow intellectual arguments were already rigged in your favor. At least be honest with yourself.

    I have seen no evidence what so ever from you that you have read Augistine, Aquinas, or anything more recent like Plantinga. For my part I have read extensively in this field of inquiry. And have read Aquinas exhaustively. Every thing that's been translated into English anyway.

    There is a plethora of high quality material out there for your perusal. Unfortunately for my poor atheists friend he can't find it without someone holding your hand? Ya OK

    Stop it, the only one who may be fooled by this bit of belly button fluff is yourself.

    Instead of doing that heavy lifting, you have lamely attempted to use my morality to shame me into doing your research and reading. Mistakenly knowing that no matter what I would have to say could be easily countered. Because you atheists are so much more enlightened and smarter than us poor ignorant anti-education Christians. Puleeze already.

    Just because I'm not willing to allow someone who has no intellectual foundation for even believing right and wrong along with moral duties even exists. To define my behavior as unchristian does not indicate I have no grip on the meaning of morality.

    I have answered your question.

    Why can't you answer mine?

    On what intellectual foundation do you claim to be able to define anyone's behavior as immoral?

    Can save you some time on this one. You can't.

    Atheist have no intellectual foundation for a belief in the existence of right and wrong, good and evil.

    You have to borrow from me to even condemn me. Use my beliefs, beliefs that you do not share, to condemn me. That seems disingenuous to me. Is this a bit over your head?

    You have provided no rational argument for your belief that my behavior towards you has been immoral. You have no intellectual foundation for a belief in morality, period.

    That's the other edge of that two edged sword you are playing with.

    I have an animosity to education? Good lord save the brain dead cliches for your fellow atheists.

    I have implored you to go out and educate yourself. To in fact read what some of the greatest minds who have ever lived have had to say on the issue. And this is an indication of my hostility towards an education? Ya right.

    Sorry you don't like the way I think or express myself. FYI I have made no apologies or excuses for my behavior here with you. I have simple stated that my treatment of you is tame in comparison to the way atheists routinely treat Christians on their blog sites. It was a suggestion that you toughen up a bit and stop acting like a such a nancy boy. It is, what it is. And again good luck to ya. No hard feelings

  14. Cam,

    Manners maketh the man.

    Nancy Boy Psi

  15. Ha ha, yes. You've a mighty fine point there Psi. Just try not to cut your finger scratching your head. By the by, the problem of evil is the problem of suffering. Same answers. What does Psi stand for anyway, pounds per square inch?

  16. Um... I'm not going to make a long post... but I will ask this: where do you prove that the possibility of something existing therefore means it exists?


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