[I posted the following for our AMU philosophy blog yesterday but I thought that it might also be of interest to some of our readers here at Thomistica, so I re-post it here..]
It is sometimes alleged that Anselm's argument for God's existence in Ch. 2 of the Proslogion -- often called his "ontological argument" -- is not a purely rational argument but in some way depends on his Christian faith. It seems to me, however, that it does not depend on faith in any formal way. In this post I will suggest some reasons why someone might think differently and then argue that none of these reasons show that Anselm's argument formally depends on faith.
But before I do that, let me comment on a couple related issues. First, some people say that Anselm does not have only one argument for God's existence in the Proslogion but two. M.J. Charlesworth, for example, thinks that in Ch. 3 there is an argument that is logically independent of the argument in Ch. 2. I have no quarrel with that view but do not intend to take a position on it here. I only wish to consider the Ch. 2 argument. Second, Aquinas and others argue (for a variety of reasons) that Anselm's argument for God's existence in Ch. 2 is unsound. I too am skeptical of its soundness. But I am not interested in that question here.
I should also add that when I speak (perhaps infelicitously) of a "purely rational argument" in contrast to an argument that depends on faith (i.e., requires premises that can only be known through faith), I do not mean to imply that arguments that depend on faith are necessarily irrational. By a "purely rational argument" I simply mean an argument that only accepts premises from what reason can know by its own investigation of things without the aid of revelation.
So, let's move on to some reasons why people might think that Anselm's Ch. 2 argument depends on his Christian faith:
1. There is the prayer to God in Ch. 1. Rational arguments do not typically include prayers to God.
2. At the conclusion of Ch. 1 Anselm says: "I do not seek to understand that I may believe, but I believe in order to understand. For this also I believe, -- that unless I believed, I should not understand." Obviously, is starting from faith and not trying to prove rationally anything held by faith. He is merely trying to understand what he believes.
3. At the beginning of Ch. 2 Anselm writes: "And so, Lord, do you, who do give understanding to faith, give me, so far as you know it to be profitable, to understand that you are as we believe; and that you are that which we believe." It would appear that Anselm is asking for God's assistance in his argument. But an argument made with God's assistance is an argument that depends on faith.
4. Anselm follows the previous sentence ( "And so, Lord, do you, who do give understanding to faith...") with: “And indeed, we believe that you are a being than which nothing greater can be thought.” And Anselm will go on to argue that God exists in they way that he is believed to be (i.e., as something than which nothing greater can be thought). So, Anselm is going to argue that God exists under a certain description. That description comes from faith. Anselm's argument, then, depends on faith.
At best the the above arguments show a material dependence but not a formal dependence of the Ch. 2 argument on faith...
Ad 1. As a Christian, it is not surprising that Anselm should begin his reflection on divinity with a prayer. But this does not entail that the prayer is a formal part of his argument. I see no part of the prayer that supplies a proposition that is necessary for the conclusion Anselm reaches at the end of Ch. 2. Suppose a mathematician prayed before he worked out a math problem. Should we assume that the prayer is a formal part of his solution to the problem?
Ad 2. Again as a Christian, faith has a priority for Anselm. Christians believe in God and believe things about God not merely on the basis of having understood or proved them. Faith is a supernatural gift that imparts real apodictic knowledge of God. And if Anselm does not believe the truths taught by revelation – that is, if he does not take them to have any bearing on reality – then, indeed, he will not understand them. Still, none of this prevents Christians from seeing whether some of what they believe might not also be knowable by reason according to its native power. You might tell me, for example, that the square root of 2 is an irrational number and I might sincerely believe you. Even so, I could still try to prove this for myself.
Ad 3. Let us suppose this (as far as we know) counterfactual: God dictated the argument in Ch. 2 to Anselm. Would that necessarily make the argument beyond reason’s grasp? No. To use my previous example again, suppose that you have proved for yourself that the square root of 2 is an irrational number and then suppose that after you have worked out the proof several times God announces to you: “The square root of 2 is an irrational number” and then proceeds to explain the proof to you. But you already knew all of this without God teaching you. If the divine revelation of a truth were sufficient to make that truth inaccessible to reason alone, you could never have known about 2’s square root before God vouchsafed it to you, and yet you did know it before that.
Ad 4. While Christians may believe that God can be correctly described as that than which nothing greater can be thought, this fact by itself would not carry with it the impossibility of rationally demonstrating this truth. We could only settle the matter by actually attempting a rational demonstration.
But let's look at Anselm's argument itself. Here is the relevant part of Ch. 2:
And indeed, [Lord,] we believe that you are a being than which nothing greater can be thought. Or is there no such nature, since the fool has said in his heart, there is no God? (Psalm 14:1). But, at any rate, this very fool, when he hears of this being of which I speak – a being than which nothing greater can be thought – understands what he hears, and what he understands is in his understanding; although he does not understand it to exist. For, it is one thing for an object to be in the understanding, and another to understand that the object exists. When a painter first conceives of what he will afterwards perform, he has it in his understanding, but be does not yet understand it to be, because he has not yet performed it. But after he has made the painting, he both has it in his understanding, and he understands that it exists, because he has made it. Hence, even the fool is convinced that something exists in the understanding, at least, than which nothing greater can be thought. For, when he hears of this, he understands it. And whatever is understood, exists in the understanding. And assuredly that than which nothing greater can be thought cannot exist in the understanding alone. For, suppose it exists in the understanding alone: then it can be thought to exist in reality; which is greater. Therefore, if that, than which nothing greater can be thought, exists in the understanding alone, the very being, than which nothing greater can be thought, is one, than which a greater can be thought. But obviously this is impossible. Hence, there is doubt that there exists a being, than which nothing greater can be thought, and it exists both in the understanding and in reality.
We could sum up the argument thus:
(i) God is that than which nothing greater can be thought.
(ii) Even the fool, who denies God, can have an understanding of that than which nothing greater can be thought.
(iii) Thus, that than which nothing greater can be thought exists in his understanding.
(iv) But it is greater to exist in reality than in the understanding alone.
(v) If that than which nothing greater can be thought existed in the understanding alone, something greater than it would exist, i.e., what exists in reality and not in the understanding alone.
(vi) But that is impossible (i.e., it is impossible for there to be something greater than that than which nothing greater can be thought).
∴ (vii) That than which nothing greater can be thought – God – must exist in reality.
Clearly, there is nothing in Anselm’s text nor in my summary of the argument that formally depends on faith in Christian revelation. To object that the second premise depends on Psalm 14 is idle because the dependence is only material. We do not need Scripture to tell us that people either do or could deny God’s existence. And, in any case, the argument only requires that someone can have an understanding of that than which nothing greater can be thought. It does not require that someone who denies God’s existence have this understanding.
Does Anselm anywhere tell us whether he thinks the Ch. 2 argument depends on faith? Let's remember that Anselm takes the Proslogion to be a continuation of the Monologion. In the preface to the Monologion he tells us that his monks asked him to compose arguments about God that did not depend on the authority of Scripture but on rational necessity. Then in the preface to the Proslogion Anselm explains that he is still trying to carry out this project. Hence, Anselm himself insists that he is not making any appeal to faith. And he will reaffirm this over a decade later when he observes in the De incarnatione Verbi that the Monologion and Proslogion were written "especially in order to show that what we hold by faith regarding the divine nature and its persons -- excluding the topic of incarnation -- can be proven by compelling reasons apart from appeal to the authority of Scripture" (Ch. 6).
So, why did I invent reasons why people might think that Anselm's ontological argument depends on faith instead of looking at the actual reasons that some of Anselm's interpreters give? This is a fair question. I think that the above exercise is useful for thinking through what is going on in Anselm's argument. But if I have time in the future, I will look at why some real people believe the argument depends on faith.