St. Anselm of Canterbury is the author of a famous proof of God's existence. Anselm argued roughly as follows. If God did not exist, then God (whom we can define as ‘the greatest being one can think of’) would simply be a figment of the human imagination (he would only exist ‘in the understanding’, as Anselm puts it). But if this were the case, something really strange would happen. A person who regarded God as imaginary would still be able to think of God as existing in reality, not just in the understanding. For example, a committed (but dissatisfied) atheist may sigh: ‘God is only a figment of the human imagination. However, I can see how the world would make more sense if God really existed.’ So, if God (the greatest being one can think of) were imaginary, it would be possible to think of a greater being (a God that were not simply imaginary, but existed in reality as well). A moment's reflection shows that this is absurd. Apparently, if God were imaginary, it would be possible to think of a being greater than the greatest being one can think of! Since the contention that God is imaginary leads to an absurdity, Anselm concluded that the statement ‘God is imaginary’ cannot be true. Given that God is either imaginary or real, it remains that He exists in reality.
Did Anselm prove once and for all that God exists? Ever since he put it forward, his argument – which at some point came to be known as ‘the ontological argument’ – has been a subject of intense philosophical controversy. In addition to analyzing its strengths and weaknesses, some thinkers have crafted different versions of the proof. Recently, Gareth Matthews and Lynne Rudder BakerFootnote 1 proposed a simplified version of the argument. They presented it in the context of an imaginary dialogue between St. Anselm and the ‘Fool’ he identified as his adversary in the Proslogion (the Proslogion is the philosophical work in which Anselm advanced the ontological argument. At the beginning of the book, Anselm introduces his discussion of God's existence by reference to Psalms xiv. 1, a biblical passage that reads ‘The fool hath said in his heart, There is no God’).
The dialogue below picks up where Matthews and Baker left off. I introduce Gaunilo as a new participant in the conversation between Anselm and the Fool (Gaunilo was a contemporary of Anselm who published a set of criticisms of Anselm's proof). My goal is to show that Matthews and Baker's simplified ontological argument, which turns on the distinction between mediated and unmediated causal powers, leaves Anselm's proof dangerously exposed to Gaunilo's best known criticism: the objection that Anselm's line of reasoning absurdly entails the existence of all kinds of imaginary entities.
GAUNILO: Good morning, Anselm. I was hoping to speak with you, but I see that you are occupied. Pray tell, who is this gentleman and what were you discussing with him?
ANSELM: This good man here is an acquaintance of mine. I was giving him a piece of my mind because he does not believe that God exists.
GAUNILO: A most unusual opinion. To disabuse him of it, did you resort to your master argument?
ANSELM: Yes, but in a simplified version I find especially convincing. First, I distinguished between mediated and unmediated causal powers. The former are causal powers that people attribute to an object of thought, as when an artist imagines Pegasus, the winged horse, as able to carry people on his back and fly. These causal powers are mediated because they depend on the artist's thoughts and imagination. If, however, a winged horse just like Pegasus existed in reality, it would have unmediated causal powers. That is, it would be a winged horse with causal powers that are truly its own and do not depend on any artist's imagination.
GAUNILO: I understand.
ANSELM: Now, would you not agree that what has unmediated causal powers is greater than what only has mediated causal powers?
GAUNILO: Yes.
ANSELM: But then God cannot simply be imaginary. For if He were, then the greatest being one can think of would only have mediated causal powers, which is contradictory in the following way. If the greatest being one can think of only had mediated causal powers, then it would be possible to conceive of something greater: a being that is the greatest one can think of and has unmediated causal powers. Since the assumption that God is imaginary leads to the contradictory claim that the greatest being one can think of is not the greatest being one can think of, the assumption must be discarded. Thus, God is not imaginary. He is real.
GAUNILO: A very clever version of your argument. But why abandon the previous version? As I recall, in the Proslogion, you cast your argument in terms of existence, and you used the distinction between existence in the understanding and existence in reality to the same effect to which you now use the distinction between mediated and unmediated causal powers.
ANSELM: I persuaded myself that I should formulate a simpler version of the argument because not all may agree that existence is a genuine property, one that would make something that exists in reality greater than something that only exists in the understanding.
GAUNILO: I understand your rationale, but it seems to me that your flank is now open to an objection I raised some time ago against the original version of your argument.
ANSELM: What objection?
GAUNILO: Strange dreams have been coming to me lately. I believe that one of them showed me the future. One night, I dreamed that many centuries from today, people will gather in large halls where a magic lantern will show them the lives and struggles of imaginary beings. In one of these spectacles, a brave young warrior and his comrades will be shown battling a lord of unparalleled cunning and brutality. The lord will be known as ‘Darth Vader’, and in the saga I am describing, his name, his black armor, and his labored breathing will inspire a terror commensurate to his status as the most evil lord that can be thought of.
ANSELM: Well, Gaunilo…
THE FOOL [to Anselm]: And you call me ‘the Fool’!?
GAUNILO: Let me explain. Whatever you make of my dreams, Anselm's simplified argument entails the absurd conclusion that Darth Vader exists in reality. For if the most evil lord one can think of only had mediated causal powers, it would be possible to conceive of someone worse: a lord who is the most evil one can think of and has unmediated causal powers. This would engender a contradiction, as Darth Vader, the most evil lord one can think of, would now not be the most evil lord one can think of. Since the assumption that Darth Vader only has mediated causal powers led us to a contradiction, Anselm's argument requires that we discard that assumption and declare Darth Vader real.
ANSELM: I understand your meaning now, but I take it that I have already refuted this type criticism, which you originally leveled at my argument through your example of the Lost Island. You stated that my line of reasoning is flawed because it entails the existence of manifestly imaginary entities, like the perfect island featured in so many seafaring legends. Don't you think that I had a good response to your criticism?
GAUNILO: I remember that you had a plausible counter argument. You said that the logic of your proof could only be applied to the greatest being one can think of. As I understand it, your defence relied on the principle that the concept of God is unique, in that only God cannot be thought not to exist. Necessary existence (a property something has when it exists and could not possibly not exist) is part of the concept of the greatest being one can think of, whereas it is not part of the concept of an island or any other entity that has a beginning in time and could in principle not have existed (we call this type of entity ‘contingent’). In your view, only the concept of God is the concept of something that is greater than everything else, because, among other things, it is the concept of a necessarily existing entity. No other thing is conceived of as endowed with this kind of absolute greatness, for no other thing requires us to conceive of it as necessarily existing in order for us to be able to conceive of it in the first place. The kind of terminal greatness that has necessary existence as one of its components does not feature in the concept of an island, a lord, or any other contingent entity. Thus, I understand your defence as turning on the principle that any island or lord one may conceive of will never be ‘the greatest’ or ‘the most evil’ that can be thought of. Take any wonderful island or evil lord you can conceive of, and I will be able to think of a better island and a more evil lord. But no one will be able to top your concept of God by adding something to it. One thinks of God as incomparably and insuperably great or one is not thinking of God at all.
ANSELM: Yes! You have given a perfect summary of my response to your objection. Are you convinced by it?
GAUNILO: I want to think about it some more. For now, my point is just that, under the original, non-simplified version of your argument, you had a promising response to the suggestion that your line of reasoning proves the existence of all sorts of imaginary entities. You could reply that there is no contradiction in supposing that the Lost Island does not exist in reality, because the Lost Island, even when one thinks of it with the most pristine beaches and the most luxuriant vegetation, is not the best island one can think of. Hence, the thought of a really existing Lost Island is not the thought of an island better than the best. Similarly, you could now say that thinking of Darth Vader as merely imaginary does not entail that, if one were to think of him as existing in reality, one would be thinking of someone more evil than the most evil person. For the concept of Darth Vader was not the concept of the most evil person in the first place. Thus, your refutation of my objection could end with the claim that it is only in the case of God that supposing His nonexistence generates a contradiction, because the supposition that God does not exist entails that something greater than the greatest can be thought (a God that exists not only in the understanding, but in reality as well). However, this supreme greatness of God, which is required by your argument, in turn requires that we think of necessary existence as a property belonging to him. One can only conceive of God as the greatest if (among other things) one conceives of Him as having necessary existence (for something that exists only contingently would obviously not be the greatest). But now that you have eliminated all talk of existence from your proof to replace it with talk of mediated and unmediated causal powers, you can no longer rely on necessary existence as a property setting the concept of God apart from the concepts of all merely imaginary entities. When he denies the existence of God, the ‘Fool’ here will say that he thinks of God as an imaginary entity with mediated causal powers in the same sense in which one would say that Darth Vader has mediated causal powers. Thus, any proof relying on your principle that what has unmediated causal powers is greater than what only has mediated causal powers entails that, if God and Darth Vader did not exist, one would be able to think of something greater than the greatest and of some person worse than the worst. Since the second contradiction demands that one should declare Darth Vader real to the same extent as the first contradiction demands that one should declare God real, you are now saddled with an argument that does not ultimately prove the existence of God, because it also entails the existence of all sorts of entities that are plainly known to be imaginary.
