Paul in his epistle to the church of Ephesus writes that “Christ gave himself the apostles, the prophets, the evangelists, the pastors and teachers, to equip his people for works of service, so that the body of Christ may be built up” (Eph. 4:11-12; NIV). Thence, by this new found maturity we have in Christ, “we will no longer be infants, tossed back and forth by the waves, and blown here and there by every wind of teaching and by the cunning and craftiness of people in their deceitful scheming” (Eph. 4:14; NIV).
Now, although this verse has a respective context, it seems that my position on the Ontological Argument is often “tossed back and forth by the waves,” since I find myself unable to make up my mind on where I stand from time to time. Initially when I was first presented the argument, I found it to be an unbelievably valuable piece of natural theology, and happened to use it fervently to fellow unbelievers. However, after a reading through Kant’s critique of the “Ontological Proof,” I later came to reject the argument, ceasing to return to its consideration for a heavy number of months.
Then, one day in particular sitting in my economics class after I finished my work, I was reading through Gordon Clark’s (1989) review of Kant’s critique of the Ontological Argument and found it to be quite a revolutionary examination of what I thence told myself I would reconsider as a valuable piece of natural theology. Furthermore, with Alvin Plantinga (1967) just a little bit later, it finally made me reconsider the Ontological Argument altogether.
However, all throughout this process of reconsideration led the creeping thought of the Ontological Argument’s ultimate weakness: Thomas Aquinas. Of course, I simply mean to say that Aquinas’ rejection of Anselm’s argument and the reason’s he furthered for that rejection is what I consider to be the best criticism of Anselm’s argument available. I would in brief like to state Anselm’s argument as such and then move on to George Smith (2001) who has an interesting critique of the argument.
If you are well familiar with Anselm’s argument and Kant’s critique, then I welcome you to skip to the bottom section regarding the Aquinas-Smith objection and provide your thoughts should you have any.
Anselm’s Ontological Argument
Around the years of 1077 and 1078 at Monastery of Bec, St. Anselm of Canterbury in his work Proslogion (1077-78) wanted to find an argument for God’s existence that would establish him in all of his greatness. William Lane Craig writes in regards to Anselm’s formulation of particular arguments for the existence of God and his dissatisfaction with them. According to his essay on the Ontological Argument, Craig writes: “Anselm remained dissatisfied with the complexity of his demonstration and yearned to find a single argument which would on its own prove that God exists in all his greatness” . Thus, Part II of the Proslogion demonstrates this argument:
the Fool has said in his heart that God does not exist? But surely when this very same Fool hears my words “something than which nothing greater can be thought,” he understands what he hears. And what he understands is in his understanding, even if he does not understand [i.e., judge] it to exist. For that a thing is in the understanding is distinct from understanding that [this] thing exists. For example, when a painter envisions what he is about to paint: he indeed has in his understanding that which he has not yet made, but he does not yet understand that it exists. But after he has painted [it]: he has in his understanding that which he has made, and he understands that it exists. So even the Fool is convinced that something than which nothing greater can be thought is at least in his understanding; for when he hears of this [being], he understands [what he hears], and whatever is understood is in the understanding. But surely that than which a greater cannot be thought cannot be only in the understanding.
For if it were only in the understanding, it could be thought to exist also in reality – something which is greater [than existing only in the understanding]. Therefore, if that than which a greater cannot be thought were only in the understanding, then that than which a greater cannot be thought would be that than which a greater can be thought! But surely this [conclusion] is impossible. Hence, without doubt, something than which a greater cannot be thought exists both in the understanding and in reality. 
Anselm to start his argument defines God as “something than which nothing greater can be thought.” Adler in commenting on Anselm’s construction of the definition of God writes: “A theoretical construct that is a complex notion will involve a number of distinct, though related, notes. The note expressed by the words ‘a being than which no greater can be thought of’ can also be expressed by the words ‘supreme being.’ Since there cannot be two supreme beings, we should not think of God as a supreme being, but rather as the supreme being – the one and only being than which no greater can be thought of” .
However, Anselm even further points out that a person who does not believe in God’s existence “understands what he hears.” Here Anselm calls attention to the very fact of an unbelievers disposition: that though before his mind he can hold notion of such a “supreme being”, he does not believe or think that such a being exists in reality. So, we can thence further Anselm’s first premise:
- (1) God exists in the understanding but not in reality.
Further down the line of Anselm’s reasoning, we also see that he distinguishes between to kinds of objects: (1) objects of thought and (2) objects that exist in reality. Otherwise stated, (1) existence in the understanding and (2) existence in reality. It is why he says, “[f]or that a thing is in the understanding is distinct from understanding that [this] thing exists.” However, Anselm goes on to illustrate the example of the painter:
For example, when a painter envisions what he is about to paint: he indeed has in his understanding that which he has not yet made, but he does not yet understand that it exists. But after he has painted [it]: he has in his understanding that which he has made, and he understands that it exists.
Hence, that which exists in reality is greater than that exists in the understanding alone. This leads us to our second premise:
- (2) Existence in reality is greater than existence in the understanding alone.
It is first important to recognize that along with other Middle Age philosophers, properties regarding existence-in-reality, power, goodness, completeness and so forth were all apart of a great chain of being, where “God is an upper bound to the great chain of being” . Anselm writes in his Monologion:
Furthermore, if one considers the nature of things, one cannot help realizing that they are not all of equal value, but differ by degrees. For the nature of a horse is better than that of a tree, and that of a human more excellent than that of a horse [ ... ] It is undeniable that some natures can be better than others. None the less reason argues that there is some nature that so overtops the others that it is inferior to none (Charlesworth 1998, p. 14).
Therefore, to structure Anselm’s argument in full (Plantinga 1967):
- (1) God exists in the understanding but not in reality.
- (2) Existence in reality is greater than existence in the understanding alone.
- (3) A being having all of God’s properties plus existence in reality can be conceived.
- (4) A being having all of God’s properties plus existence in reality is greater than God – from (1) and (2)
- (5) A being greater than God can be conceived (3), (4).
- (6) It is false that a being greater than God can be conceived – by definition of “God”
- (7) Hence it is false that God exists in the understanding but not in reality – (1)-(6), reductio ad absurdum.
Anselm’s argument is thence suggesting that (2) existence in reality is greater than existence in the understanding alone. This isn’t simply a matter of intuition that the adherent of the argument hopes his interlocutor agrees with, but connotes Anselm’s idea regarding the chain of being that we saw back in his statement in the Monologion. Thus, an acceptance of (2) leads us to a consideration of premises (3)-(6), where, taken along with (1) and (2), collectively make the contradiction that a being existing in reality is greater than the greatest conceivable being, which exists in the understanding.
Kant’s Critique of the Ontological Argument
In his Critique of Pure Reason, Kant argues that stipulating existence as a predicate to its subject does not give the subject actual existence. For instance, supposing the statement “all triangles have three sides” is true (which it is), a contradiction emerges once I deny the predicate in respect to its subject. In other words, I cannot be consistent in suggesting that “triangles do not have three sides”; which would then no longer constitute a triangle.
However, a denial of the subject (triangle) in respect to its predicate is not a contradiction. It is in the same way with God – you cannot stipulate the predicate of existence to the subject “God” and then suppose that it exists in reality. This is a simple understanding in regards to the concept of things. Namely, that things may or may not exist or things must or must not exist. Respectively, contradictory things cannot exist in reality (or any other for that matter). Mortimer Adler further comments on the Kantian critique:
Immanuel Kant objected [ ... ] on the grounds that existence is not a predicate and that it adds nothing to the perfection of the subject of which it is predicated. It must, of course, be conceded that the word “exists,” in a sentence such as “a president of the United States exists,” or such as “horses exist,” is not like any other predicate, such as “strong” and “swift” said of horses, or such as “wise” and “courageous” said of a president of the United States. These predicates characterize their subjects, as “exists” does not. 
However, in response to Kant’s argument, Gordon Clark (1989) argues that Kant is not clear in (1) exposing an adequate critique of Anselm’s argument and (2) did not disprove the existence of God (nor was it ever his intention, but that in respect to his aim at Anselm, Kant had not disproved God’s existence). For instance, Kant writes that “[f]f in an identical judgement, I annihilate the predicate in thought, and retain the subject, a contradiction is the result; and hence I say, the former belongs necessarily to the latter. But if I suppress both subject and predicate in thought, no contradiction arises; for there is nothing at all, and therefore no means of forming a contradiction” .
However, Clark in response asks Kant what exactly he means when he says “to annihilate something in thought.” Clark explains in full:
What does it mean to annihilate something in thought? Does it mean merely not to think about it? Refusing to think surely is a prescription for avoiding self-contradiction, but what bearing such a refusal has on God, or even on angles, is hard to say. Maybe then annihilation means denial of existence. If I positively deny that there are any triangles, it is not absurd to deny triangularity. If now I positively deny that God exists, it is not absurd to deny his existence. But this doesn’t fit the triangle example. With respect to triangles Kant has insisted that the denial of the subject eliminates the predicate. But when Kant turns to the main matter and demands, Deny God exists; he asks us to deny, not the subject, as in the triangle example, but the predicate. Thus this argument does hang together. 
However, though Clark exposes the inadequacy of Kant’s critique, what about the very substance of his objection? Is not the “existence not a predicate” argument still applicable in our consideration of God’s existence? Alvin Plantinga (1967) argues something quite on the contrary:
…Anselm can certainly agree, so far as his argument is concerned, that existence is not a real predicate in the explained sense. Anselm maintains that the concept the being than which none greater can be conceived is necessarily exemplified; that this is so is in no way inconsistent with the suggestion that the whole concept of a thing diminished with respect to existence is equivalent to the undiminished whole concept of that thing. Anselm argues that the proposition God exists is necessarily true; but neither this claim nor his argument for it entails or presupposes that existence is a predicate in the sense just explained. 
Thus, to finish with E.J. Lowe (2007): “Nothing in… the ontological argument implies that… existence… must be a divine attribute or property, in the way that omniscience or omnipotence are… [T]he Kantian objection… is just a red herring with no real bearing on the soundness of the ontological argument” (p. 337).
The Aquinas-Smith Objection
Gordon Clark elsewhere has written that “Thomas Aquinas and Bishop Berkeley both believed in God, but neither of them believed that this argument proved the existence of God” . Why? It was Aquinas’ position that “the senses are not the total cause of all of our knowledge,” however, “they do provide the indispensable material from which the intellect abstracts the intelligible content” . Thus, it follows from this that “human beings cannot know the essence of a substance that is not perceptible by the senses” . Thus, since God’s existence is inseparable from his existence (as they are identical), we have no direct or immediate insight as to the existence of God through His essence.
However, George Smith (2001) states Aquinas’ objection in a likewise interesting fashion. First, is “God exists” a self-evident proposition? According to Aquinas, a proposition can be understood in two ways: A proposition may either be (1) absolutely or (2) contextually self-evident. Smith goes on to explain:
A proposition, though self-evident in itself, will not be contextually self-evident to those who do not understand the meaning of the relevant concepts. And this is what we find with the proposition “God exists.” God’s essence is identical to his existence, so if we could understand what God is, we would also know that God exists without further deliberation. But the nature of God cannot be grasped by the human intellect, so the existence of God is not contextually self-evident to human beings .
The question of God’s existence then as understood under the Ontological Argument does not become a theoretical one, but a factual one. To finish, “[c]an our limited intellect truly grasp what it means to say that God’s essence is existence? No, says Aquinas, so we cannot base a demonstration for the existence of God on nothing more than an analysis of God’s nature” . Now, of course it is to be noted to Smith had a focus on Anselm’s dismissal of the “Fool’s” denial of God’s existence; hence regarding atheism as a “logically inconsistent” position. Smith argues at the end of his exposition of Anselm’s argument that “[g]iven our inability to understand the nature of God, atheism cannot be summarily dismissed as an incoherent position” .
I have yet to find an adequate response to this objection to Anselm’s argument. Of course there has been some good work in integrating modal logic into the argument; removing its once “conceptual realist” base in place of something I find far more solidly grounded. Comments would be welcome as to your thoughts on this issue.
-  William Lane Craig, The Ontological Argument in To Everyone An Answer, ed. W. L. Craig, F. Beckwith, and J.P. Moreland (IVP Press: 2004) p. 124
-  Quoted from Complete Philosophical and Theological Treatises of Anselm of Canterbury, trans. by Jasper Hopkins and Herbert Richardson (Arthur J. Banning Press: 2000) pp. 93-94
-  Mortimer Adler, How to Think About God (Touchstone: 1991) p. 70
-  Robert Maydole, The Ontological Argument in The Blackwell Companion to Natural Theology, ed. W.L. Craig and J.P. Moreland (Wiley-Blackwell: 2012) p. 554
-  Adler, 73
-  From The Impossibility of an Ontological Proof, in Critique of Pure Reason (p. B. 629)
-  Gordon Clark, Three Types of Religious Philosophy, 2nd edn. (Trinity Foundation: 1989) p. 39
-  Alvin Plantinga, God and Other Minds, 2nd edn. (Cornell University Press: 1992) p. 36
-  Gordon Clark, Thales to Dewey, 2nd edn. (Trinity Foundation: 1989) p. 257
-  Jan A. Aertsen in The Cambridge Companion to Aquinas (Cambridge University Press: 1997) p. 32
-  Ibid., p. 32
-  George Smith, Why Atheism? (Promotheus Books: 2001) p. 156
-  Ibid., p. 157
-  Ibid.