In this question and reading about the ontological argument elsewhere I have discovered that there is (and has been) a lot of discussion about it, and that it was taken very seriously.

Can someone explain to me how thinking about something perfect (or being able to conceive it) must mean that it exists?

(This is obviously a non sequitur in my opinion, even if existence is a perfection; why should me thinking about something perfect make that thing exist? But, if that were the case, I expect the argument to never be taken seriously in the first place.)

How can this argument that "thinking about a perfect being means that it has to exist" have been taken so seriously for so many years (instead of being dismissed right away)?

I expect to be misunderstanding something or lacking the necessary knowledge, so I would also welcome any pointers to the necessary knowledge I'm lacking.

  • I have reformulated your question somewhat, mostly just reframing the headline to reflect the content of the question a bit better; have also updated tags and tried to cleanup the body a little bit.
    – Joseph Weissman
    Sep 16, 2011 at 2:50

4 Answers 4


Richard Dawkins, in his book The God Delusion, articulates an "infantile version" of the ontological argument in a way that might reveal it's reasoning and major flaw:

The God Delusion, p. 104, by Richard Dawkins

Now, consider the classic formulation of the ontological argument...

  1. God is that which nothing greater can be thought, i.e. the greatest possible being (by definition).
  2. God exists as an idea in the mind.
  3. A being that exists as an idea in the mind and in reality is greater than one which only exists in the mind.
  4. Therefore, God must exist in both the mind and reality.

... which more clearly highlights the critical (3rd) premise, which is often tacitly implied in many formulations.

This argument is often discussed in entry-level studies in philosophy because it is both very old and specious in nature. It is a valid argument, but it is not sound because not all the premises are true. In fact, all the major criticisms boil down to the same thing: the 3rd premise.

  • Gaunilo posited that such an argument with the 3rd premise as is would also imply the most perfect island, or pencil, or anything.
  • Kant said that "existence is not a predicate", i.e. that existence does not anything to the nature of a thing, it is a relation between the object and the subject. In other words, you cannot say that to exist is better/greater than to not exist; it simply doesn't make sense.

The other major line of criticisms is the empiricist argument, often attributed to Hume and echoed by many philosophers today. These people balk at the idea that such grand conclusions can be reached with absolutely certainty without any empirical evidence. Richard Dawkin's calls it "logomachist trickery", and points out the counter-argument by Douglas Gasking which "proves" the non-existence of God using the same basic reasoning:

  1. The creation of the world is the most marvelous achievement imaginable.
  2. The merit of an achievement is the product of (a) its intrinsic quality, and (b) the ability of its creator.
  3. The greater the disability (or handicap) of the creator, the more impressive the achievement.
  4. The most formidable handicap for a creator would be non-existence.
  5. Therefore if we suppose that the universe is the product of an existent creator we can conceive a greater being — namely, one who created everything while not existing.
  6. Therefore, God does not exist.

SEP and Wikipedia cover this pretty well; there should be more than enough there to help clarify the "power" of the ontological argument for you, but keep in mind that once you realize the trick (which you already seem to have done), the argument really loses all its persuasiveness.

  • I'm having troubles with the definition of "thinking" in these contexts. Just thinking the words "the concept of the most perfect being" is enough for this? I would assume that that's not the case because it doesn't really aprehend the concept, just merely describes it. I expect to be making a newbie mistake here, so references are welcome.
    – Vinko Vrsalovic
    Sep 14, 2011 at 18:38
  • 1
    I'm not using any complex terms here. Thinking = conceiving. Here, let me edit my post with an amusing (and perhaps revealing) example from Richard Dawkins...
    – stoicfury
    Sep 14, 2011 at 23:08
  • Thanks for the example. But I'm not saying you are using complex terms, I wonder what exactly is conceiving in this case. Is it merely saying the words in your mind? or is it actually trying to imagine how would it look like, feel like and be like?, or maybe it is making a list of the characteristics of such a being. I think this is important because you can certainly conceive a car because you have seen one (but how well you can conceive it depends on how well you understand it) and you can conceive a monster because you don't have any specific requirements, [continues...]
    – Vinko Vrsalovic
    Sep 15, 2011 at 4:55
  • ...but how can you conceive the most perfect being (or the most hideous monster) if you cannot know for sure what that is?
    – Vinko Vrsalovic
    Sep 15, 2011 at 4:55
  • 1
    'Conceiving' as in having a loose understanding of something. Thinking of it as "saying the words in your mind" is not useful here; I need not 'voice' it in my head to conceive of something. For example, can you conceive of the idea of the space shuttle? You do not fully understand all that which goes into making an obviously very complex space shuttle, but you can still conceive of the idea of a space shuttle in your head. Do the same with God, and follow the rest of the steps in the argument. :P
    – stoicfury
    Sep 15, 2011 at 7:10

Before answering the question, we should clear up the terminology a bit. The validity of an argument refers to its logical structure; the soundness depends on the truth-value of its propositions.

So, it would seem that you are not asking about the soundness at all (since you are willing to stipulate that the premises are sound, for the sake of argument) but as to its validity.

As you may suspect, the ontological argument rests upon an often unstated premise: that to exist is more perfect/greater than not to exist.

If this premise is granted, the argument is valid.

If we begin with the notion of some X such that X is "that than which a greater cannot be thought", and draw in our premise from above, X must exist, because otherwise we could simply think of something that shares all of the properties of X plus existence.

Note that this doesn't actually get us very far; so far all we've proven is that X is the greatest thing imaginable-- Anselm still has the work of attributing to this X all of the other properties he wishes to attribute to God.

And, of course, it rests on a series of shaky premises.

The SEP article on the subject is a great starting point, and offers several different attempts at formalization of Anselm's argument.

  • 1
    Fixed the title. And thanks, I was not fully comprehending the part of X being, by definition, "that than which a greater cannot be thought". By the way, the ability of thinking about "something than which a greater cannot be thought" is taken as a given, but it seems really hard to actually do (other than uttering those (or similar) words in the mind.)
    – Vinko Vrsalovic
    Sep 14, 2011 at 10:01
  • Good answer! But I wonder whether it is true that if one has a notion X and one can think of it, one can also think of X-that-exists. It certainly doesn't seem obvious to me. For example, if we place in a computer the largest program that it can contain, and then we try to add another println("Hello, world!") statement, the program will no longer fit.
    – Rex Kerr
    Sep 14, 2011 at 14:24

It's a rather trivial declaration. It's saying that if God were a most perfect being, He should also exist, since how can God be perfect if He doesn't exist?

From a logical standpoint, it's a bit like pointing at a rock and claiming it to have the magical properties of dispelling any evil monsters. When questioned about it's effectiveness, you can always say that since there are no evil monsters, it has proven its worth. Both arguments hinge on the existence (or in this case non-existence) to prove something. Of course, that's a fallacy.

  • 1
    It's a bit different than that in my understanding. It's saying that the being X is "the greatest thing that can be thought". It then says that, as existence is a perfection, X must exist. And then, surprise, X fits the definition of God. But I share @Rex Kerr worries about the intrisic validity of the argument. Let's say Y is X without existing, how can you be sure you can think Y + existence? I'm not even sure a human being could really conceive Y (even if we would agree on what Y is.)
    – Vinko Vrsalovic
    Sep 14, 2011 at 15:27

Here's an ontological disproof of God:

God is a being capable of the greatest achievements imaginable.

The greater the handicap overcome, the greater the achievement. So, for example, climbing Mount Everest is a modest achievement for most people, but a great achievement for a man with one leg. For a man with no legs, it is an even greater achievement.

God, being capable of the greatest achievements possible, must have the greatest handicap imaginable.

The greatest handicap imaginable is not existing.

Therefore God must not exist. If he did exist, a non-existent God would be capable of even greater achievements than he is, which is a contradiction.

  • Is that a citation?
    – Joseph Weissman
    Sep 18, 2011 at 1:04
  • I believe this type of argument (that non-existence can be a perfection property just as reasonably as existence can) originated with Douglas Gasking. A similar argument can be found here. Sep 18, 2011 at 1:11
  • It's obviously illogical to conclude that a non-existent God could do anything. This is hardly a persuasive argument. Atheists have to jump through many hoops to avoid the existence of God. Come on. Sep 6, 2018 at 0:58
  • @HamSandwich Which step in the proof, precisely, do you think is the illogical one? Of course the conclusion is going to be illogical -- there's no point in an ontological proof that reaches a logical conclusion. Sep 6, 2018 at 2:05
  • That’s your opinion. Sep 6, 2018 at 13:29

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