Background
Anselm of Canterbury was an Italian Benedictine monk, philosopher, and theologian credited with the ontological argument’s origin in the 11th century A.D. The ontological argument considers whether a maximally great being—or, as Anselm described it, “a being than which nothing greater can be conceived”—exists.
The argument is philosophical, it doesn’t appeal to empirical (i.e., sensory or experimental) evidence but depends on reflection, logic, and reasoning. As with other types of theistic arguments, there are many versions of the ontological argument. In modern times, the one offered by philosopher Alvin Plantinga has garnered significant attention.[1] Plantinga attempts to show that if it is possible that a maximally great being exists, then a maximally great being exists necessarily.
The Argument and Discussion
In this essay, a “maximally great being” will be defined as a being that has at least the following properties: all knowledge (i.e., omniscience), all power (i.e., omnipotence), and moral perfection (i.e., omnibenevolence). Ask yourself, “Can these three perfections be manifested in a being, at least in some possible world?”[2] There are essentially three responses to this question; one can (1) agree that the existence of such a being is possible, (2) disagree that the existence of such a being is possible (i.e., it is impossible for such a being to exist), or (3) remain agnostic about the question. The author will briefly discuss the implications of each response below.
First Response: Agree. Suppose a questioner agrees that a maximally great being may exist in some possible world. In that case, she must simply follow the reasoning below. The argument demonstrates that if it is possible for a maximally great being to exist, then such a being necessarily exists. The argument can be stated like this:[3]
Premise 1: It is possible that a maximally great being exists (i.e., a being with the maximally great properties listed above).
Premise 2: If Premise 1 is true, then a maximally great being exists in some possible world. In other words, if it is possible that a maximally great being exists, then that being possesses maximally great properties in some possible world (see footnote 2).
Premise 3: If such a being exists in some possible world, it exists in every possible world.
Premise 4: If such a being exists in every possible world, it exists in the actual world.
Therefore, A maximally great being necessarily exists.
Second Response: Disagree. One can disagree with Premise 1 and claim: “It is impossible that a maximally great being exists.” If one makes such a claim, then she also bears the burden of proof to show that the existence of such a being is not possible.
The problem with this position is that unless one possesses all knowledge, how can one claim that the existence of such a being is impossible? No finite person knows all there is to know. Indeed, no contingent[4] being even knows the limits of what can and cannot be known. For finite beings, reality is always an open field of discourse. Therefore, denying that a maximally great being exists in some possible world would seem pointless.
Furthermore, a maximally great being cannot be contingent; otherwise, it would not be maximally great. If there is some possible world in which the properties of maximal greatness are manifested, those properties must also be manifested in every possible world. In other words, if a being possesses maximally great properties, it would be impossible for this being not to possess them in every possible world. Such a being is necessary; all finite or contingent beings must rely on this being for their existence.[5]
Third Response: Agnostic. One may claim to be agnostic about whether a maximally great being exists. An agnostic would claim to lack knowledge about the existence of such a being. Nevertheless, agnosticism can be dismissed as a view that does not add to the conversation. Since an agnostic is not claiming for or against the existence of a maximally great being, she is offering no significant input to the question.
Other Objections. Apart from objecting to Premise 1, one might question Premise 3 by asking, “Even if a maximally great being does exist in some possible world, why must it also exist in every possible world?” The response should be evident: It is greater for a being to exist in more possible worlds than just one. A being wouldn’t be maximally great if it only exists in some possible worlds. Therefore, if a maximally great being exists in any possible world, it must exist in every possible world.[6]
But one may further object, “What about unicorns?! Surely, they must exist in some possible world, so why not in every possible world?” Unicorns may indeed exist in some possible world. However, unicorns are, by their nature, contingent beings. Therefore, even though unicorns and other contingent things (e.g., Santa Claus, fairies, and Leprechauns) may exist in some possible worlds, they cannot exist in every possible world. Indeed, only a maximally great being can and must exist in all possible worlds.
Conclusion
Not everyone who reflects on the concept of a maximally great being will accept it. Plantinga concedes that a rational person need not consent to this argument; he claims only that a rational person could accept it and be rationally justified.
However, the ontological argument is a logically valid deductive argument.[7] Thus, if the premises are true, the conclusion follows by necessity. Moreover, unless one can defeat any of the premises or provide good reasons against the argument, the theist is rationally justified in believing in the existence of a maximally great being, while the non-believer might not be rationally justified.
The skeptic can choose to deny that a maximally great being is possible, in which case she must provide reasons to justify such a claim. Further, the skeptic may retreat to agnosticism, but this would not threaten theism since the agnostic offers no substantive argument one way or the other.
The ontological argument is not intended to “prove” the existence of a maximally great being but, instead, claims to establish the rational acceptability of believing in such a being. In other words, those who accept this argument can be rationally justified in holding such a belief.
About the Author
David P. Diaz, Ed.D., is an independent researcher and retired college professor. His writings have ranged from peer-reviewed technical articles to his memoir, which won the 2006 American Book Award. Dr. Diaz holds a Bachelor’s and Master of Science degrees from California Polytechnic State University, a Master of Arts in Philosophical Apologetics from Houston Christian University, and a Doctor of Education specializing in Computing and Information Technology from Nova Southeastern University. [back to top]
Footnotes
[1] Alvin Plantinga, God, Freedom and Evil (Grand Rapids, MI: William B. Eerdmans, 2008), Part II, c.
[2] A possible world does not refer to a parallel dimension or some specific place in a multiverse; it simply refers to a possible description of reality. To say that a being exists in a possible world is just to say that if the world were that way, then such a being would have existed.
[3] Adapted from Plantinga, God, Freedom and Evil, Part II, c. See also William Lane Craig, Excursus on Natural Theology (Part 22): The Ontological Argument (October 20, 2023, transcript), https://www.reasonablefaith.org/podcasts/defenders-podcast-series-4/excursus-on-natural-theology/excursus-on-natural-theology-part-22-the-ontological-argument.
[4]Contingent or finite things are those that could not have existed on their own (i.e., they have the potential to not exist) and are, therefore, dependent on something else for their existence. Since they have the potential to not exist, contingent beings will not exist in some possible worlds.
[5] A necessary being is one that could not have failed to exist. In other words, it is a being for whom it is impossible not to exist. Therefore, a necessary being serves as the cause of all non-necessary (i.e., contingent) things that exist in all possible worlds.
[6] See Alvin Plantinga, “The Modal Ontological Argument,” Center for Philosophy of Religion, February 9, 2018, https://youtu.be/tdAeNQmftzg?si=kTbuRXabong6a72-. See also William Lane Craig, drcraigvideos: “The Ontological Argument,” August 16, 2016, https://youtu.be/xBmAKCvWl74.
[7] “Valid deductive arguments are those where the truth of the premises necessitates the truth of the conclusion: the conclusion cannot but be true if the premises are true. Arguments having this property are said to be deductively valid. A valid argument whose premises are also true is said to be sound.” Catarina Dutilh Novaes, “Argument and Argumentation,” The Stanford Encyclopedia of Philosophy (Fall 2022 Edition), Edward N. Zalta & Uri Nodelman (eds.), https://plato.stanford.edu/archives/fall2022/entries/argument/.