Natural Theology or God and His Existence Part 1: Anselm’s Ontological Argument

Natural Theology or God and His Existence Part 1: Anselm’s Ontological Argument

[This essay is developed in terms of a book, so the formatting will be odd, also I cut out Descartes OA for the sake of space, and the fact it is not very good]

God and His Existence

  1. The Ontological Argument
  2. The Various Cosmological Arguments, the types and their veracity
  3. The Teleological Argument
  4. The Argument from Eternal Truths (Divine Conceptualism)
  5. The Henological Arguments
  6. Arguments from the Existence of Moral Values and Duties
  7. The Immediate Experience of God



This chapter will treat the topic of God’s existence in the various major ways it has been discussed through history. While the writer is clearly sympathetic to the defense of the theistic proofs, a survey of opinions will be addressed, using many points from atheists and skeptics within the Philosophy of Religion. While CAB (The head writer) is a committed theist, not all of the proofs will be immediately accepted, and many will be outright rejected as we will see. This is clear when reading a proof like the cosmological argument, which has quite the supply of iterations and versions. Given the high amount then, it will be quite hard to agree with all of them. However, as we will see, the quantity is strength here. Another word of warning is needed before we begin, one of immense importance. The chapter will be full of Metaphysical terminology that will perhaps be glossed over, so the reading list at the back might be quite helpful to the lay reader (assuming I ever finish writing this). With so many historical periods being traversed through these proofs, the terminology will simply have to change frequently. Cosmological arguments which seek to explain the universes beginning will shift from the Aristotelian language of Al Ghazali and Bonaventure, to the language of Modern Astrophysics. With this word of caution in place, we will proceed to the various arguments for the existence of God, separated from the breadth of evidence for revealed religions, within the context of Natural Theology.

  1. The Ontological Argument

The Ontological Proof’s for the existence of God are a tradition of arguments based around the concept of God as a maximally great being, and moving onwards from this to His existence. Originally written in 1078 by Saint Anselm of Canterbury in his Proslogion, this argument has been debated with great frequency, with no shortage of detractors, and quite a few major supporters. Thinkers like Descartes, Gödel, Bonaventure, Norman Malcom, Robert Maydole, Dun Scotus and Alvin Plantinga  have all offered support for versions of this argument. For the sake of this discussion however, we will focus on two versions:

  1. The Classical Anselmian Formulation
  2. Alvin Plantinga’s Modal Ontological Proof

We will proceed from here to a long treatment of Anselm’s argument,  then move hence forth to the one deemed most successful in modern philosophy, Alvin Plantinga’s formulation using S5 Modal Logic.

  • The Classical Anselmian formulation

The version of this argument which typically receives the most treatment in philosophy classrooms today is the version  belonging to Saint Anselm of Canterbury. While there is some debate on the purpose of this argument, whether it was truly an argument or a sort of a petitionary prayer, most commentators do agree Anselm was trying to convince even the fool that God, the concept he is aware of even if he does not fully understand all of the implications, entails His existence. Anselm argues the fool does have this concept in his intellect from a reading of Psalm 14:1 “The fool has said in his heart, “There is no God.”…”, because any sort of denial presupposes a subject to be denied.  A key reason many interpret this as a prayer rather than an argument against unbelievers is that the historical context. Like Aquinas’s proofs, the middle ages was not a period of significant strife among religious skeptics, if you could even say something akin to an atheist existed in 11th. Century Europe. Like Aquinas, who was battling groups sympathetic to other deity concepts like the Pantheists, or educating Theology students, Anselm did not have His goal as an evidential apologetic. It is debatable if even Pantheism was in the crosshairs, as Anselm’s proof has been quite convincing to Pantheist’s like Spinoza. Rather what Anselm was doing was formulating a shorter work than the long proof of the Monologium, which served as quite an extensive argument in length and substance. The Proslogion is very brief however, with most of it being a treatment of what would later be known as perfect being theology. Secondly, to support the position this is a prayer rather than an argument, an assumption can be made based on the very use of the Psalm. Anselm was never questioning the inspiration of sacred scripture, in fact it is probable following Augustine, he sees this authority piggy backing off the “miracle of the Church”, in that it was converting the whole world with fisherman as some of its key early catalysts. Only God could make such a movement powerful, Anselm likely thought. It is not of the present task to decide the correct reading, as it is still obviously a (mostly) working logical argument. With this background information now in place, we will move onto the argument.

While the exact intended formulation of this argument is contested among Historians of Philosophy, it is of the opinion of the author that the version presented by Father Brian Davies presents this in the most defensible way possible. It is helpful to note still there is debate among historians and philosophers on what Anselm’s intended formulation was, and the formulations given will likely vary across introductory works. Here is the argument as presented by Davies:

  1. On the assumption that that than which nothing greater can be conceived is only in a mind, something greater can be conceived;
  2. For some­thing greater can be thought to exist in reality as well;
  3. The assumption is therefore contradictory: either there is  no such thing even in the intellect, or it exists also in reality ;
  4. But it does exist in the mind of the fool;
  5. Therefore that than which nothing greater can be conceived exists in reality as well as in a mind.

From this we can proceed. To start out this argument relies on quite a few metaphysical terms. An example of this would be how Anselm proceeds from Premise 1 to Premise 2. Anselm is using a sort of Platonic view of gradation to serve as a fulcrum, comparing mind independent reality with that of the conceptual realm within the intellect. Anselm illustrates what he takes to display the truth value of mind independent realities combined with conceptual realities supremacy by using the example of a painter and his artwork. To quote the Proslogion “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”. The painting can be enjoyed in the world as well as delighted about in the intellect upon its assumption into reality.  Dun Scotus also notes that a Being, having only mind dependent existence, seems to have an intrinsic limiter, namely the intellect, and hence Divine Infinity, clearly a property of a perfect being, is nonfunctional, which would also seem to support Anselm’s task, that His greatness would entail His being.  Anselm however takes this as a simple truism, and hence the fool, who has the concept of God in his mind if you give the Biblical account credence, when truly grasping the idea of what the concept of a greatest conceivable being entails, will be forced to admit His existence. From here Anselm tries to create a reductio ad absurdum (Reduction to the Absurd). This concept of the Divine exists, and yet it is only existent in the intellect. Existing in reality has no signs of any imperfection (This will be noted yet again during our treatment of the Divine Attributes), and like the painting, there is reason to suppose it would be greater to have being apart from the intellect. But if the being exists only in the mind, then a greater can be conceived. The idea either does not exist in the intellect, or it exists in reality as well. Since one contradicts background information we already know (namely the concept of God exists in the intellect), the way out of the dilemma is to accept that this being exists in reality as well. Therefore, God, who is the maximally great being this proof sets to argue for, exists.

Now this argument was very controversial even in its day, and obviously with any argument so meaningful if true, there have existed skeptics. Yet most accept there was not a decisive critique until Immanuel Kant offered one in his Critique of Pure Reason. Still, it is worth mentioning the opinions of two of the greatest detractors of this proof, Gaunilo of Marmoutiers and Saint Thomas Aquinas, who were functioning during the point of the arguments greatest fame.  Aquinas’s argument is much briefer and of less note, so we will treat it first. Aquinas, arguing from an Aristotelian epistemology, points out we cannot form any argument from God’s essence to His existence, because we have not abstracted or entertained His essence. While Aquinas certainly does think that God’s existence (Note Aquinas takes God’s esscence to be His existence, but he comes to this position based off A Posteriori proofs) will be self-evident if humans experience the beatific vision, due to them perceiving God in His fullness, it isn’t self-evident to most individuals on earth (if not all), nor will it be unless we receive the special grace Aquinas posited to explain the experience of Abraham and Moses. Still, even with Aquinas’s great note, there still is a certain weakness to his objection. Aquinas perhaps takes for granted how controversial Aristotelian metaphysics was and still is, and hence it seems without arguing for an entire ontology, we will have to limit our discussion of it there. Anselm, being a Middle Platonist along the lines of Augustine, would not accept the idea of abstraction being key to epistemology and would instead opt more for an Iluminationist view of the mind and its grasp of the abstract concepts (We will touch upon this in our examination of divine conceptualism). It would be silly to not argue against Anselm on his own terms, unless we defend a whole ontology.  The more interesting critique will be that of Gaunilo of Marmoutiers, a monk who wrote against the argument while living as a contemporary of Anselm. We will focus on this critique and Anselm’s reply in the next sub section.


Gaunilo’s Piland

The most viable pre-Kantian criticism of Anselm’s argument came from a Monk operating contemporaneously with Anselm in the person of Gaunilo of Marmoutiers. While even Anselm accepted how cordially Gaunilo operated in his critique, there is a level of bitterness in their correspondence. For example, Gaunilo titles his rebuttal “On Behalf of the Fool”, an obvious slap at Anselm’s Proslogion. Still, it can hardly be denied that Gaunilo’s counter argument offers a sort of persuasiveness to it. To show Gaunilo’s refutation it would be helpful to display by looking at Anselm’s argument. Gaunilo used the terminology offered in Anselm’s proof but replaced God with a Piland, which is the greatest island conceivable (He actually said just the greatest Island, which Anselm pointed out, but it is helpful to strengthen the arguments of an opponent). With this in place, we will see what Gaunilo was stating. Using this argument you could prove something as absurd as an imaginary island from the concept of it alone. Gaunilo and many others took this as a solid defeater to Anselm’s position, and hence the glory of victory seemed belong to Gaunilo (if you could say Theologians have victories of this sort). Still, most have thought Anselm’s reply was solid enough to still make the argument quite respectable even if still, quite odd.  Anselm replies that things like Island’s are like the series of natural numbers. It is not quite evident that there can be an intrinsic maximum on these sorts of items. You can always conceive of a greater entity that exemplifies these particular ideas, a higher number in the series or more wildlife or tree’s on the Island. Is this necessarily the case with God?  Perhaps not. To give an example, think of God’s omnipotence. Typically theists have defined God’s power as entailing the ability to create any logically possible thing. If we define power as many modern theists do as the ability to bring about all possible state of affairs, does there seem to be any greater property that God could “exemplify” with regard to causal prowess (Note: I use this term loosely, God is typically though to possess Aseity, or self-existence apart from abstract objects like properties) ?  I think not. Surveying all of the other properties typically thought of as better to have than not to have seems to justify this intuition even more. Goodness, knowledge, and the whole host of typical divine attributes seem to fit plausibly under properties that can have intrinsic maximum’s. There is perhaps a layer of vagueness with regards to properties like justice, but again, these seem to be plausibly incorporated under Anselm’s defense as well. For example, if you accept the Christian view of a triune God, each person of the Godhead would be rendering to the other members of the Godhead His due to a maximal extent, namely infinite love. This perhaps toes the line into natural and revealed theology, but it is worth mentioning as a solution to this problem, and one a Catholic like Anselm would probably be sympathetic to (Note: There still is come vagueness with regard to the number of members of the God head for example, on this alone, but the point still has some weight, namely that a normally transitive property can function essentially). This objection while still used in moderation, has never been regarded as decisive in the opinions of most philosophers, most recognizing Anselm’s defense as at least plausible. Gaunilo’s Piland has been replaced by the objection of Immanuel Kant as the default objection to be dealt with by contemporary defenders of this argument. With that in mind, we will move on to the objections first presented in Kant’s Critique of Pure Reason, namely whether being or existence functions properly as a predicate in an argument, or whether it’s denial leads to self-contradictory results.



Kant’s Objection

The objection of Immanuel Kant is by far the most famous objection to the ontological argument. Most philosophers accept it as decisive. Is this the case however? We will ultimately see. The first argument Kant presents in his Critique of Pure Reason is translated as follows:


“If,  in  an identical proposition, I  reject the predicate while retaining the subject,contradiction results;  and I  therefore say that the former belongs necessarily to  the latter. But if we reject the subject and predicate alike,  there  is no contradiction for nothing is then left that can be contradicted.  To posit a  triangle, and yet to  reject its  three angles,  is self-contradictory;  but there  is no contradiction in rejecting the triangle together with its three angles. The same holds true of the concept of an

absolutely  necessary being. If its existence  is rejected, we reject the thing itself with  all  its predicates;  and no question of contradiction can then arise. There is nothing outside it that would be contradicted,  since the  necessity of the thing is not supposed to  be derived from anything external;  nor is there anything internal that would be contradicted,  since in rejecting the thing itself we have at the same time rejected all its internal properties

… I cannot form the least concept of  a  thing which,  should it  be rejected with all its

predicates,  leaves behind a contradiction”

To summarize, Kant is arguing that rejecting the existence of something is not akin to rejecting a proper accident of it. A triangle being 3 sides makes any sort of negative proposition denying this self-contradictory, because it is of the very nature of a triangle to have three sides. Rejecting existence however seems to lead rejecting the whole substance and all of its features, and hence it seems God could be consistently denied existence.



Now this seems to have some bearing to Anselm’s proof at face value, but upon a further look, this conclusion is less obvious. Historically, the first argument Kant used is probably lodged for the most part not at Anselm, but the ontological arguments of Descartes and Christian Wolff. Read in this context, it is quite obvious what Kant is saying. In Descartes Meditations on the First Philosophy, he reasons from the essence of God to His existence, by way of asserting that He cannot conceive of God’s essence separate from His existence, because it seems to include it by its very nature. Descartes also uses the example of a triangle which makes this even more obvious. Kant’s critique seems to quite frankly, tear down the arguments of the other two thinkers. Is it, however clear this line of argumentation works against Anselm? Perhaps not. To quote Father Brian Davies on the subject “most people writing on Anselm assume that he does (Try to define God into existence). But we may, in fact, challenge this assumption. Early in the argument of Proslogion 2 Anselm introduces a premiss assert­ing existence (‘Something than which nothing greater can be conceived exists in the intellect’). And his question in Proslogion 2 is not whether we can move from a definition of God to the reality of God,  but whether we can reasonably suppose that something  than which nothing  greater  can be conceived exists only in the intellect.” If this is the right way of reading Anselm, perhaps Anselm does have an ample rescuing device to his proof.

This however is the less popular objection Kant fired against Ontological proofs (in other words Anselm is not out of the firing zone). Kant’s main objection is his second one, whether it is a valid belief that being or existence is a true predicate.  To quote again from Kant’s Critique of Pure Reason:

“‘ Being’ is obviously not a real predicate; that is, it is not a concept of something which could be added to the concept of a thing. … . By whatever and however many predicates we may think a thing … we do not make the least addition to the thing when we further declare that the thing is.”

In this quotation Kant argues that adding is or exists does not add anything new to the concept of God. What it does is merely constitute a new relation. This is not however the case with attributes like red or omnipotence, which seem to function and have conceptual value. Existence does not seem to function as a predicate in any real sense, and Anselm, at least critics have said, seems to place existence “on to” God. There is also a feel of Pre-Fregian fregianism, in asserting that existence as perfection or predicate seems to have strange consequences for nonexistent objects. An example of this would be a Phoenix. To talk about the existence of a Phoenix using being as a first level predicate, something along the lines of the sentence “The existing Phoenix’s do not, in fact, exist,” would have to be a functional proposition. This sentence is  self-contradictory and obviously absurd however, and its implications ought to make one skeptical of existence being a first order predicate. Now the Scholastics did use existence as an accidental predicate, affirmed of a subject, and hence, a discussion on these two views will be needed. The question however, is whether, Anselm is open to this criticism. Contrary to popular opinion, it is not so clear it is. To quote Alvin Plantinga:

“According to the great German philosopher and pessimist Arthur Schopenhauer, the ontological argument arises when “someone excogitates a conception, composed out of all sorts of predicates, among which, however, he takes care to include the predicate actuality or existence, either openly or wrapped up for decency’s sake in some other predicate, such as perfection, immensity, or something of the kind.” If this were Anselm’s procedure-if he had simply added existence to a concept that has application contingently if at all-then indeed his argument would be subject to the Kantian criticism. But he didn’t, and it isn’t.”

Also to quote G.H. Joyce, an opponent of the argument, notes that a crucial error when accessing this argument is treating it as if the absurd results of applying listing existence as a proper predicate arbitrarily to finite objects:

“Kant criticizes the ontological proof at length in the Critique of Pure Reason. It is frequently assumed that his refutation was decisive; but in point of fact his arguments are wide of the mark. He throughout treats the notion of the infinite nature as though it were on a par with other natures, and could be represented either with or without existence. He fails to meet the fundamental contention of those who defend the proof, viz., that the nature of the infinite is inconceivable apart from real existence”

And yet again:

“They (the modern opponents of the argument) think it sufficient to adopt an illustration employed by Kant, and to say that we cannot prove the existence of a hundred dollars from the idea of them, no matter how good the dollars are supposed to be. Of this imaginary refutation of the ontological proof Professor Sorley well says: “It really misses the point of that proof which was an effort to discriminate between the idea of God and all other ideas.”


To summarize, Kant’s point about predication perhaps has some value. Applying predicates to random essences (existence being one such predicate), seems to be an ill adviced way to form propositions or arguments. However, Anselm is not doing this; he is meditating on the attributes and the implications of a Metaphysically Ultimate being, and arguing mind independent reality follows for God. This is not like adding an act of being arbitrarily to the whole host of items within the conceptual realm, generally finite ones. This point is also arguable against Gaunillo, whose argument seems especially prone to an error of this sort as well.

  Due to a variety of arguments against the applicability of these old rebuttals, is now true, since the 1960’s a complete shift in reading Anselm has occurred. It is now true that a great many philosophers, theistic in persuasion or otherwise, accept that Kant’s criticism has more limited strength than the historical consensus has attributed to it. This does not mean it is never used, and as we said earlier, there is a definite application available here to attack arguments like that or Descartes. In spite of this however, it seems clear Anselm’s argument is at least immune to the objections of Kant.

As I have noted, it is not of the current project to answer, the interpretation of Kant, thinking along the lines of Frege, about existence being merely a second order predicate. This is because we will treat this important discssion in a further chapter on the Divine Attributes, since it is especially tied to Divine Simplicity. For now however, we will move on from the major criticisms of Anselm’s arguments and go on to the version typically recognized as the most defensible by modern proponents of this family of arguments, the modal version popularized by Alvin Plantinga, arguably anticipated by Anselm himself.

To conclude, while Anselm’s proof is a metaphysic dependent argument (to be fair, what argument is not?), most of the common points against it are at the very least answerable, if not conclusive. If you accept a system like that of Aristotle’s, then plausibly yes, the a priori element in this proof will be subject to intense skepticism. However, arguing on Anselm’s terms and granting his middle Platonistic leanings, it seems to be at least a defensible line of argumentation, and one with some fruits to the enterprise of Natural Theology.





Will continue in part 2 with Plantinga’s version



Davies, Brian. An Introduction to the Philosophy of Religion. Oxford: Oxford U Press, 2004. Print.
Joyce, George Hayward. Principles of Natural Theology. Neunkirchen-Seescheid, Germany: Editiones Scholasticae, 2016. Print.
Plantinga, Alvin. God, Freedom and Evil. Grand Rapids, Mich: William B. Eerdmans, 2008. Print.

MobileReference. Critique of Pure Reason: by Immanuel Kant. Boston:, 2008. Print.






3 thoughts on “Natural Theology or God and His Existence Part 1: Anselm’s Ontological Argument

    1. Yes, this is true. Anselm perhaps thinks that the Divine Essence is an idea we have, even if we don’t comprehend it fully. Duns Scotus gives the example of ineffiability. We can not know what an ineffiable thing is, and yet we have a concept of ineffiable. Similarly, we have a vague concept of God, even if we don’t comprehend His infinitude. Similarly, since Anselm thinks we have this idea in our mind, the only reason we haven’t inferred God’s existence is because we haven’t meditated on the concept fully. Now, how plausible that is is another debate. I am not that sympathetic to the OA. Rather I think it is defensible only in the context of one providing other arguments to it’s defense. Duns Scotus does that, and to a degree so does Leibniz. His argument for eternal truths and Cosmological Arguments both point towards a Greatest Conceivable Being properly understood. The reason is that the cause of both of them can’t be a possible essence but existence itself. Since the first cause is simple, and Anselm argued the project of Perfect Being Theology led to a simple GCB, these beings must be the same per Leibniz’s Law, or at the very least indiscernible. But yes, Leibniz is important here. As for Craig’s point, I think Craig typically appeals to self consistency if I remember correctly. This is controversial point but it seems defensible. I haven’t read Craig’s defense of the OA in quite a long time. Craig has an even bigger commitment to the argument than Plantinga does, in the sense that Craig thinks it is a plausible piece of natural theology in its own right (even if it’s best support is the cumulative weight of other arguments). This is something I never liked about Craig’s project, even though I admire the man greatly and owe a lot to him. His natural theology is much too varied and hectic in nature.

      Anyways thanks for the comment and God bless you,



      1. Thanks for the response. Yeah, you’re right that the ontological argument is best used in a cumulative case, perhaps as the final step. I’m wondering if one can plug in the argument in an inductive manner, perhaps by utilizing epistemic probabilities. One will wonder what the datum will be in the ontological argument, and maybe the datum is something like “having the concept of a maximally great being” or “having the idea of that which nothing greater can be thought”.


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