top of page

The Ontological Argument

Take a moment to think about God. What is God like? What is His nature? In our often busy and hectic lives, we rarely take time alone to think about God. St. Anselm of Canterbury, a Catholic monk, theologian, and philosopher who lived from about 1033 to 1109, recognized this. In his work, Proslogion, he invites the reader in the first few pages to take some time alone to think about God. Much of this first chapter is a prayer to God to reveal truth to Him as he tries to be alone and think on Him. His first words to the reader are:

"Come now, insignificant man, leave behind for a time your preoccupations; seclude yourself for a while from your disquieting thoughts. Turn aside now from heavy cares, and set aside your wearisome tasks. Make time for God, and rest a while in Him. Enter into the inner chamber of your mind; shut out everything except God and what is of aid to you in seeking Him; after closing the chamber door, seek Him out." (90)

Taking time alone for God left St. Anselm in awe of God's greatness and glory. Christians today rarely practice the discipline of solitude before the Lord. When Christians practice it, they do what Christians have always done, as well as the psalmists before them: worship the Lord for all of His divine attributes. When we make God the center of the focus of our minds and hearts, we recognize what the Bible already says about Him: God, and God alone, is worthy of worship. God's oneness (i.e., monotheism) itself entails that there is none greater than God, and the Old Testament, written as it was in a time when most people believed in multiple lesser gods, makes this very clear. In Psalm 145:3, the psalmist proclaims (ESV):

"Great is the Lord, and greatly to be praised, and his greatness is unsearchable."

Deuteronomy 10:17 is written in the context of the rewriting of the Ten Commandments on the two tablets of stone. Moses comes down from the mountain to tell the people what the Lord had said to him, teaching the people God's law and how to worship Him. Moses says (NASB):

"'For the Lord your God is the God of gods and the Lord of lords, the great, the mighty, and the awesome God who does not show partiality nor take a bribe.'"

We see in this verse a direct comparison to the other "gods" of the peoples surrounding Israel, including Egypt, which had formerly enslaved the Israelites. God is the "God of gods," meaning that He is greater than all other gods. In fact, however, there are no other gods, as the Lord says in Isaiah 45:5-7 (NASB):

"'I am the Lord, and there is no other; Besides Me there is no God. I will gird you, though you have not known Me; That men may know from the rising to the setting of the sun That there is no one besides Me. I am the Lord, and there is no other, The One forming light and creating darkness, Causing well-being and creating calamity; I am the Lord who does all these.'"

This is a sobering thought that should stop us in our tracks: God is great. He alone is sovereign over all things, and He alone exists as Creator of all that exists. Set your mind on Him as you read these passages.

St. Anselm, as he sets his mind on the Lord and prays to Him, recognizes that God, in his words, is "something than which nothing greater can be thought" (93). That is, if you can think of some being greater than God, then that being is God. This seems to be in accord with Scripture. For St. Anselm, such a being could be conceived, or thought of in the mind, and therefore exists, at least in the mind. In the same way, a unicorn can be conceived in the mind and therefore exists in the mind, even if unicorns do not exist in reality. But, for St. Anselm, only a God which exists in reality, as opposed to merely in the mind, can be considered great. So, in order for God to be great, He must exist in reality. If something than which nothing greater can be thought can be conceived in the mind, then that "something" must therefore exist in reality. For it not to exist in reality would be a contradiction in terms.

St. Anselm considered this argument to be knock-down, so much so that he would relate it in Proslogion to Psalm 14:1, which says (NASB), "The fool has said in his heart that there is no God." To St. Anselm, the fool in question has failed to realize that to think of God and yet believe that He does not exist is a contradiction. Later, in the 17th century, Descartes would pose this argument with minor changes in his book Meditations on First Philosophy (1641). For the most part, however, the argument was treated with derision, if it wasn't just ignored. Immanuel Kant, in his seminal work Critique of Pure Reason (1781), levied a critique against Descartes's modified version of the argument, which is widely considered to be successful.

Why, then, are we discussing the ontological argument? It would seem like the argument was a failure. Even Christian philosophers such as Alvin Plantinga admit this. We are still discussing the argument because, in spite of the success of St. Anselm's and Descartes's formulations of the argument, the ontological argument is still hotly debated in other forms today. Probably the most popular version is Alvin Plantinga's modal version of the argument, which he first proposed in his book God, Freedom and Evil (1974). In this book, Plantinga grants critiques against St. Anselm's and Descartes's formulations of the argument, namely, that they are question-begging (i.e., that they presuppose God's existence in order to prove it) and Kant's objection that existence is not a property.

Kant's critique employs a thought experiment involving pennies. He argues that there is no conceptual difference between a penny conceived in the mind and one which exists. One can think of a penny's properties-its chemical makeup, shape, color, and the like-and see that the concept of a penny lacks nothing if it does not exist. If it exists (i.e., if you take a penny out of your pocket and observe it), the difference doesn't have to do with gaining a new property; the penny simply exists. Since Descartes claimed that the property of existence is necessary for God to be the greatest conceivable being, then this objection, if successful, is devastating to his formulation, since God is just as great if He exists or not. There is no conceptual difference between God, conceived in the mind, and a God who exists in reality.

Alvin Plantinga. Image can be found on Wikipedia.

Plantinga admits that this seems right but points out that the way in which one exists is a property of one's being. In our discussion of the argument from contingency, we discussed the difference between something that exists contingently and something that exists necessarily. This has to do with one's explanation for its existence. I'll use myself as an example. I can think of any number of circumstances in which I would not have come to exist. For instance, my parents could have never met, or it is possible that they not have fallen in love. One of my parents could have died before conceiving me. Either one of my parents could have been unable to have children. If I want to go further back, either one of my parents could have not been born. This thought experiment could go on ad infinatum, since there are an innumerable amount of circumstances that could have resulted in my failing to exist. Because of this, my existence is contingent; it is possible that I could have failed to exist. A large part of this is that the explanation of my existence is an external cause, my parents in an immediate sense and God in an ultimate sense.

On the other hand, other things exist out of the necessity of their own nature. It is part of what it means to be that thing to exist. Many mathematicians, for example, believe that numbers exist. If numbers exist, then it would make sense to think of them as necessary beings, since one could hardly conceive of a set of circumstances in which numbers don't exist. Even if nothing at all exists, the number of things that exist is zero. The vast majority of theologians believe that God, if He exists, is a necessary being. Therefore, although there is no conceptual difference in the object whether it exists or not, there is absolutely a conceptual difference in the object whether it exists necessarily or contingently.

Plantinga helps to clarify in his language many of the concepts present in St. Anselm's and Descartes's work. First, he adopts St. Anselm's concept of "something greater than which nothing can be thought," but he calls this the "greatest conceivable being" (hereafter GCB) or the "maximally great being." I will use GCB to describe this being, even though both terms refer to the same being. Second, he refers to those properties of the GCB as "great-making properties," which are properties of the GCB that contribute necessarily to its greatness. These are properties which persons tend to have in degrees, such as being loving and good, but which the GCB must have to the maximal degree. This grounds what are called the superlative attributes of the GCB, which are properties such as omniscience, omnipotence, and the like. Therefore, in order for the GCB to be the GCB, the GCB must have all great-making properties to the maximal degree. To lack in any of these properties, or to have any of them to less than the maximal degree, is to be less than the GCB. If God is, by definition, the GCB, then to lack in any way would be to fail to be truly God.

The question, then, for Plantinga, is this: is there a difference in greatness between the being that exists contingently and the being that exists necessarily? In other words, would a being that exists necessarily be greater than one which could fail to exist? In Plantinga's mind, the answer seems intuitively to be yes; a necessary being would be greater. Imagine if God existed but was contingent in His existence. This would entail that in some set of circumstances, God literally would not exist at all. Why is God's existence seemingly a luck of the draw? And what causes Him to exist in one set of circumstances and not others? If His existence is due to an external cause, then couldn't we just look to the cause, and wouldn't that cause be greater than this being we're mistakenly calling God? Because of this, conceiving of God as contingent seems to be absurd. Therefore, the GCB, if it exists at all, must exist necessarily.

To further clarify this difference between necessity and contingency, Plantinga employs a concept in modal reasoning called possible world semantics. Possible world semantics conceives of necessary and contingent existence in terms of possible worlds. These "worlds" don't actually exist, as if they're multiple universes, but they are complete descriptions of possible sets of circumstances. For instance, it is possible that the meteor that hit the Yucatan Peninsula and is thought to have killed the dinosaurs could have instead passed over Earth, thereby not affecting the dinosaurs, such that the dinosaurs lived on for millions of years. In that possible set of circumstances, different things would have resulted. We can express this, using possible world semantics, by saying that in some possible worlds, the meteor didn't hit the Yucatan Peninsula, and the dinosaurs lived on for millions of years. Even though that didn't actually happen, it could have happened. This is why statements about what could have happened are called counterfactual claims; in fact, they may not be true, but they could have been true.

In possible world semantics, each complete description of a possible set of circumstances will include propositions that are, in fact, true and propositions that are, in fact, false. For instance, we may say that in some possible worlds, President Trump was actually removed from office and not merely impeached. Possible worlds that include the proposition, "President Trump is removed from office," which is in fact not true, still include propositions that are in fact true, such as the proposition, "Donald Trump is president for the term of 2016-2020." Only the complete description of a possible set of circumstances that includes all true propositions, and no false ones, is a description of the actual world; it describes the way things really are.

When we apply possible world semantics to contingent and necessary existence, we find that this conceptual difference has to do with whether all, some, or no possible worlds include the proposition that a certain object exists. For instance, my existence is contingent, which therefore entails that I do not exist in some possible worlds. The existence of numbers, however, is necessary. If they exist at all, then they exist in all possible worlds, and if they do not, then they exist in no possible worlds. An easy example of this is logical contradictions. Do married bachelors exist? No. Since the concept of a married bachelor is a logical contradiction, then it is impossible for them to exist, and therefore they exist in no possible worlds.

Therefore, according to Plantinga, the GCB or God, if it exists at all, must exist in all possible worlds. This helps us by showing that it actually incoherent to think that the existence of the GCB is merely possible. Since the GCB, if it exists at all, must exist necessarily, then either the GCB exists in no possible worlds or all of them. Most atheists are willing to grant that it is at least possible that God exists. But, since God is the GCB, and since the GCB must exist necessarily in order to be the GCB, then God, if He exists in some possible worlds, must exist in all possible worlds, including the actual world. Therefore, God exists.

This is a lot of information, I know, so it might help to reread this section with a pen and paper for notes, so that you can follow the line of thought. Now that we've covered everything needed to conceptually grasp this argument, here is the video:

First, I'll list the premises and conclusion of the argument here. Instead of "maximally-great being," I will substitute "GCB" for the sake of consistency. Here is the argument:

  1. A GCB exists in some possible worlds.

  2. If a GCB exists in some possible worlds, then it exists in every possible world.

  3. If a GCB exists in every possible world, then it exists in the actual world.

  4. Therefore, a GCB exists in the actual world.

For the sake of clarifying the logic of the argument, I've removed a premise and a conclusion. The premise that "it's possible that a GCB exists" means that a GCB exists in some possible worlds. The conclusion that "a GCB exists" means that a GCB exists in the actual world. Both of these propositions simply express the same thing as a premise and conclusion in the argument, so I removed it.

This argument follows a rule of logical inference called a hypothetical syllogism. Using p and q, here is the rule:

  1. p ->q

  2. q->r

  3. Therefore, p->r

This rule effectively cuts out the middleman. If you can show that there is a line of implication running from p to r through q, then the truth of p implies the truth of r. Only p, then, needs to be established as true in order for everything else to follow from p. This is very important in Plantinga's version of the ontological argument, since it shows that only premise 1 must be shown to be true in order for it follow that God exists.

With that in mind, let's symbolize the argument. Let's use P for "a GCB exists in some possible worlds," E for "a GCB exists in every possible world," and A for "a GCB exists in the actual world." Here's the argument symbolized:

  1. P

  2. P->E

  3. E->A

  4. Therefore, A

So we see that as long as P is true, A necessarily follows. Therefore, we can say that if it is possible that God exists, then God actually exists. Thus, the argument is logically valid.

What about its soundness? Notice that premises 2 and 3 make sense in light of our discussion on the nature of a GCB. If a GCB must exist necessarily, then these inferences follow directly from the concept of a GCB itself. For this reason, philosophers do not generally attack premises 2 and 3. The premise in question, then, is premise 1.

In order for the atheist to deny the ontological argument, then, the atheist must show that it is impossible that God exists. How in the world can the atheist do this? The only way, it seems, would be for the atheist to argue that the concept of God is logically contradictory or incoherent. If this objection is right, it would show that the concept of God is much like a square circle or married bachelor and that therefore, God could not possibly exist. Some atheists have attempted to make objections like this, but they have been unsuccessful. Barring that objection, then, there seems to be no reason to think that God's existence is impossible. But then it follows logically that God actually exists.

What are some strengths of this argument? Admittedly, this argument is difficult to explain to someone who doesn't have philosophical training or experience. One has to grasp some pretty abstract concepts before they will be able to understand this argument. Yet it is my favorite argument for God's existence! Here's why. First, I love the fact that this argument invites me to consider the greatness of the God I worship and serve. Whenever I revisit this argument (as I have many times now), I am inevitably stricken with awe for a God so awesome, so great, as to defy comprehension and invite the thinking Christian into an ocean of His truth, presence, and essence. Such a God as great as this loves me and every other person individually. So this argument invites me into a deep meditation on the glory of God and His nature, and it's worth the headache intellectually to get there.

Second, the idea that God is the greatest conceivable being seems to so clearly line up with Scripture that it's difficult to imagine any Christian disagreeing with the conceptual framework of the argument, at least. This is doubly true when you consider the fact that this theological concept is so applicable to other areas of Christian theology, such as christology and the Trinity. Having these concepts in mind will help Christians to think about doctrine and theology a bit more clearly, I think.

Third, a huge strength in this argument is its intuitive weight and force. Once the needed concepts are grasped, then the conclusion that God must exist very naturally follows. This argument also shows, in a very clear way, how untenable the atheist position really is. If God either exists necessarily or doesn't exist necessarily, then the atheist cannot claim that God's existence, though possible, isn't actual. If the atheist claims that God does not exist, then he or she must defend the notion that God could not possibly exist. Any option between the two is incoherent conceptually, since God is, by nature, a necessary being as the greatest conceivable being. Because of this, I personally find the ontological argument to be powerfully persuasive, and I think that the atheist is under a burden of proof far to weighty for him or her to bear.

That's it for this week's post! I hope that you found the argument interesting, and I hope that my explanation was as accessible as it could be. More importantly, I hope that this argument has encouraged you to take time alone to think about God and to do the same as you get to know Him in prayer. It has certainly encouraged me in that way. Next week, we will discuss the argument for God's existence from the resurrection of Jesus. After that, we will begin to discuss arguments against God's existence, focusing primarily on the problem of evil and suffering. Stay tuned for that!

If you find yourself continuing to come back to the blog, please consider subscribing to it, so that you will get notified of each new post. With a subscription, you can also comment below and start a discussion! Finally, if you have any questions or comments about the blog, then you can send me a message from the bottom of the homepage. I look forward to receiving messages from you. Thank you for reading!

39 views0 comments

Recent Posts

See All


bottom of page