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Ontological argument

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An ontological argument is a philosophical argument for the existence of God that uses ontology. Many arguments fall under the category of the ontological, and they tend to involve arguments about the state of being or existing. More specifically, ontological arguments tend to start with an a priori theory about the organization of the universe. If that organizational structure is true, the argument will provide reasons why God must exist.

The first ontological argument in the Western Christian tradition[1] was proposed by Anselm of Canterbury in his 1078 work Proslogion. Anselm defined God as "that than which nothing greater can be thought", and argued that this being must exist in the mind, even in the mind of the person who denies the existence of God. He suggested that, if the greatest possible being exists in the mind, it must also exist in reality. If it only exists in the mind, then an even greater being must be possible—one which exists both in the mind and in reality. Therefore, this greatest possible being must exist in reality. Seventeenth-century French philosopher René Descartes deployed a similar argument. Descartes published several variations of his argument, each of which centred on the idea that God's existence is immediately inferable from a "clear and distinct" idea of a supremely perfect being. In the early eighteenth century, Gottfried Leibniz augmented Descartes' ideas in an attempt to prove that a "supremely perfect" being is a coherent concept. A more recent ontological argument came from Kurt Gödel, who proposed a formal argument for God's existence. Norman Malcolm revived the ontological argument in 1960 when he located a second, stronger ontological argument in Anselm's work; Alvin Plantinga challenged this argument and proposed an alternative, based on modal logic. Attempts have also been made to validate Anselm's proof using an automated theorem prover. Other arguments have been categorised as ontological, including those made by Islamic philosophers Mulla Sadra and Allama Tabatabai.

Since its proposal, few philosophical ideas have generated as much interest and discussion as the ontological argument. Nearly all of the great minds of Western philosophy have found the argument worthy of their attention, and a number of criticisms and objections have been mounted. The first critic of the ontological argument was Anselm's contemporary, Gaunilo of Marmoutiers. He used the analogy of a perfect island, suggesting that the ontological argument could be used to prove the existence of anything. This was the first of many parodies, all of which attempted to show that the argument has absurd consequences. Later, Thomas Aquinas rejected the argument on the basis that humans cannot know God's nature. Also, David Hume offered an empirical objection, criticising its lack of evidential reasoning and rejecting the idea that anything can exist necessarily. Immanuel Kant's critique was based on what he saw as the false premise that existence is a predicate. He argued that "existing" adds nothing (including perfection) to the essence of a being, and thus a "supremely perfect" being can be conceived not to exist. Finally, philosophers including C. D. Broad dismissed the coherence of a maximally great being, proposing that some attributes of greatness are incompatible with others, rendering "maximally great being" incoherent.

Contemporary defenders of the ontological argument include Alvin Plantinga, William Alston and David Bentley Hart.


The traditional definition of an ontological argument was given by Immanuel Kant.[2] He contrasted the ontological argument (literally any argument "concerned with being")[3] with the cosmological and physio-theoretical arguments.[4] According to the Kantian view, ontological arguments are those founded on a priori reasoning.[2]

Graham Oppy, who elsewhere expressed the view that he "see[s] no urgent reason" to depart from the traditional definition,[2] defined ontological arguments as those that begin with "nothing but analytic, a priori and necessary premises" and conclude that God exists. Oppy admitted, however, that not all of the "traditional characteristics" of an ontological argument (analyticity, necessity, and a priority) are found in all ontological arguments[5] and, in his 2007 work Ontological Arguments and Belief in God, suggested that a better definition of an ontological argument would employ only considerations "entirely internal to the theistic worldview".[2]

Oppy subclassified ontological arguments into definitional, conceptual (or hyperintensional), modal, Meinongian, experiential, mereological, higher-order, or Hegelian categories, based on the qualities of their premises.[5] He defined these qualities as follows: definitional arguments invoke definitions; conceptual arguments invoke "the possession of certain kinds of ideas or concepts"; modal arguments consider possibilities; Meinongian arguments assert "a distinction between different categories of existence"; experiential arguments employ the idea that God exists solely to those who have had experience of him; and Hegelian arguments are from Hegel.[2] He later categorised mereological as arguments that "draw on… the theory of the whole-part relation".[6]

William Lane Craig criticised Oppy's study as too vague for useful classification. Craig argued that an argument can be classified as ontological if it attempts to deduce the existence of God, along with other necessary truths, from his definition. He suggested that proponents of ontological arguments would claim that, if one fully understood the concept of God, one must accept his existence.[7] William L. Rowe defined ontological arguments as those that start from the definition of God and, using only a priori principles, conclude with God's existence.[8]


Although a version of the ontological argument appears explicitly in the writings of the ancient Greek philosopher Xenophanes and variations appear in writings by Parmenides, Plato, and the Neoplatonists,[9] the mainstream view is that the ontological argument was first clearly stated and developed by Anselm of Canterbury.[5][10][11][12] Some scholars argued that the Islamic philosopher Avicenna (Ibn Sina) developed a special kind of ontological argument before Anselm,[13][14] but other scholars have doubted this position.[15][16][17] Daniel Dombrowski marked three major stages in the development of the argument: Anselm's initial explicit formulation; the eighteenth-century criticisms of Kant and Hume; and the identification of a second ontological argument in Anselm's Proslogion by twentieth-century philosophers.[18]


Anselm of Canterbury was the first to attempt an ontological argument for God's existence.

Theologian and philosopher Anselm of Canterbury (1033–1109) proposed an ontological argument in the second and third chapters of his Proslogion.[19] Some commentators maintain that Anselm's argument was not presented in order to prove God's existence; rather, they interpret Proslogion as a work of meditation in which he documented how the idea of God became self-evident to him.[20] But in the fourth chapter Anselm states unequivocally that "No-one who understands that which God is can think that God does not exist, although he may say these words in his heart. For God is that than which a greater cannot be thought. Whoever understands this properly, understands at least that this same thing so truly exists that not even in thought can it not exist. Therefore, whoever understands that God exists in the same way cannot think that God does does exist."

Anselm's argument is often often summarised along the following lines:[21]

  1. It is a conceptual truth (or, so to speak, true by definition) that God is a being than which none greater can be imagined (that is, the greatest possible being that can be imagined).
  2. God exists as an idea in the mind.
  3. A being that exists as an idea in the mind and in reality is, other things being equal, greater than a being that exists only as an idea in the mind.
  4. Thus, if God exists only as an idea in the mind, then we can imagine something that is greater than God (that is, a greatest possible being that does exist).
  5. But we cannot imagine something that is greater than God (for it is a contradiction to suppose that we can imagine a being greater than the greatest possible being that can be imagined.)
  6. Therefore, God exists.

The argument above has the form: x is something F, something F exists, therefore x exists. That form of argument is invalid. If that were Anselm's argument, he would not have proven that God exists. [22] Anselm does not conclude chapter 2 by asserting that God exists. Nor does he assert in Chapter 2 that it is a conceptual truth, or a definition, that God is a being than which none greater can be imagined. He says explicitly that that is what "we believe". In fact, he deduces that that belief is true in chapter 3. So, that belief cannot be the first premise of his argument, since it is a conclusion he is working towards.

While that is how this argument is widely understood, it has been argued that interpretations along those lines seriously misrepresent what Anselm has written, because commentators do not pay close enough attention to the text. [23] The best translation to date is by Ian Logan [24] To quote the text, Anselm's argument for those conclusions goes as follows. In Chapter 2 of the Proslogion, Anselm declares a belief to the God to whom he is praying: "Indeed, we believe You to be something than which nothing greater can be thought".[25] But then he interrupts his prayer , because he remembers that the Bible mentions a fool who says in his heart that God does not exist. So, he asks himself, "Is there not anything of such a nature?'. For if there is not, then it follows that that than which a greater cannot be thought is not in reality. From this point onward Anselm does not mention God again until the middle of chapter 3.

Nevertheless, he understands that something is believed to have this nature, and he argues that even this fool can understand this concept. So, Anselm has this thing in mind ("in the understanding") even if it is not in reality. But even if this thing is only in the understanding, it can be thought that it is in reality. And if it were in reality, he says, it would be greater than if it were not. It follows that since it can be thought to be in reality, it can be thought to be greater than it is if it were only in the understanding. In that case, he says, "If that than which a greater cannot be thought is only in the understanding, that same thing than which a greater cannot be thought is something than which a greater can be thought. But that cannot be." [26] Since supposing that this thing is not in reality has entailed a contradiction, he concludes his chapter 2 by asserting that something than which a greater cannot be thought is in reality. But he does not identify that something as God in chapter 2.

In Chapter 3, Anselm presented a further argument in the same vein:

  1. This same something than which a greater cannot be thought can be thought to be something than which could not be thought not to exist.
  2. If that than which a greater cannot be thought can be thought not to exist, it would not be as great as if it could not be thought not to exist.
  3. If that than which a greater cannot be thought can be thought not to exist, it would not be something than which a greater cannot be thought.
  4. Therefore, something than which a greater cannot be thought could not be thought to exist.
  5. That conclusion is equivalent to its being necessarily true that this something cannot be thought not to exist.
  6. Furthermore, it follows from the previous argument that it is necessarily true that this thing is in reality.
  7. Whatever is in reality exists.
  8. So, it is necessarily true that this something exists.
  9. So, it is necessarily true that this something exists, and cannot be thought not to exist.
  10. Therefore, something than which a greater cannot be thought so truly exists that it could not be thought not to exist.

This contains the notion of a being that cannot be conceived not to exist. He argued that if something can be conceived not to exist, then something greater can be conceived. Consequently, a thing than which nothing greater can be conceived cannot be conceived not to exist and so it must exist. This can be read as a restatement of the argument in Chapter 2, although Norman Malcolm believed it to be a different, stronger argument. [27]

Contrary to what is often said, neither of those arguments mentions God. But Anselm then identifies something than which a greater cannot be thought as God. He offers two reasons for that. One is that if someone could think of something better than God, the creature would ascend above the Creator, which Anselm says is absurd. This reason would have appeal only to those who already believe that God is the Creator. But his second reason does not presume anything about God. Resuming his prayer, Anselm says that "Whatever is other than You can be thought not to exist" [28] For that reason it follows that God, and only God is something than which a greater cannot be thought exists. Thereby. Anselm has proven that the belief he earlier declared is true. From that identification it follows that God, and only God, so truly exists that He cannot be thought not to exist.

Gottfried Leibniz[edit]

German philosopher Gottfried Leibniz attempted to prove the coherence of a "supremely perfect being".

Gottfried Wilhelm Leibniz saw a problem with Descartes' ontological argument: that Descartes had not asserted the coherence of a "supremely perfect" being. He proposed that, unless the coherence of a supremely perfect being could be demonstrated, the ontological argument fails. Leibniz saw perfection as impossible to analyse; therefore, it would be impossible to demonstrate that all perfections are incompatible. He reasoned that all perfections can exist together in a single entity, and that Descartes' argument is still valid.[5]

Mulla Sadra[edit]

Mulla Sadra (c. 1571/2 – 1640) was an Iranian Shia Islamic philosopher who was influenced by earlier Muslim philosophers such as Avicenna and Suhrawardi, as well as the Sufi metaphysician Ibn 'Arabi. Sadra discussed Avicenna's arguments for the existence of God, claiming that they were not a priori. He rejected the argument on the basis that existence precedes essence, or that the existence of human beings is more fundamental than their essence.[29]

Sadra put forward a new argument, known as Seddiqin Argument or Argument of the Righteous. The argument attempts to prove the existence of God through the reality of existence, and to conclude with God's pre-eternal necessity. In this argument, a thing is demonstrated through itself, and a path is identical with the goal. In other arguments, the truth is attained from an external source, such as from the possible to the necessary, from the originated to the eternal origin, or from motion to the unmoved mover. In the argument of the righteous, there is no middle term other than the truth.[30] His version of the ontological argument can be summarized as follows:[29]

  1. There is existence
  2. Existence is a perfection above which no perfection may be conceived
  3. God is perfection and perfection in existence
  4. Existence is a singular and simple reality; there is no metaphysical pluralism
  5. That singular reality is graded in intensity in a scale of perfection (that is, a denial of a pure monism).
  6. That scale must have a limit point, a point of greatest intensity and of greatest existence.
  7. Hence God exists.

Mulla Sadra describes this argument in his main work al-asfar al-arba‘a [four journeys] as follows:

Existence is a single, objective and simple reality, and there is no difference between its parts, unless in terms of perfection and imperfection, strength, and weakness… And the culmination of its perfection, where there is nothing more perfect, is its independence from any other thing. Nothing more perfect should be conceivable, as every imperfect thing belongs to another thing and needs this other to become perfect. And, as it has already been explicated, perfection is prior to imperfection, actuality to potency, and existence to non-existence. Also, it has been explained that the perfection of a thing is the thing itself, and not a thing in addition to it. Thus, either existence is independent of others or it is in need of others. The former is the Necessary, which is pure existence. Nothing is more perfect than Him. And in Him there is no room for non-existence or imperfection. The latter is other than Him, and is regarded as His acts and effects, and for other than Him there is no subsistence, unless through Him. For there is no imperfection in the reality of existence, and imperfection is added to existence only because of the quality of being caused, as it is impossible for an effect to be identical with its cause in terms of existence.[31]

Kurt Gödel[edit]

Mathematician Kurt Gödel provided a formal argument for God's existence. The argument was constructed by Gödel but not published until long after his death. He provided an argument based on modal logic; he uses the conception of properties, ultimately concluding with God's existence.[32]

Definition 1: x is God-like if and only if x has as essential properties those and only those properties which are positive

Definition 2: A is an essence of x if and only if for every property B, x has B necessarily if and only if A entails B

Definition 3: x necessarily exists if and only if every essence of x is necessarily exemplified

Axiom 1: If a property is positive, then its negation is not positive

Axiom 2: Any property entailed by—i.e., strictly implied by—a positive property is positive

Axiom 3: The property of being God-like is positive

Axiom 4: If a property is positive, then it is necessarily positive

Axiom 5: Necessary existence is positive

Axiom 6: For any property P, if P is positive, then being necessarily P is positive

Theorem 1: If a property is positive, then it is consistent, i.e., possibly exemplified

Corollary 1: The property of being God-like is consistent

Theorem 2: If something is God-like, then the property of being God-like is an essence of that thing

Theorem 3: Necessarily, the property of being God-like is exemplified

Gödel defined being "god-like" as having every positive property. He left the term "positive" undefined. Gödel proposed that it is understood in an aesthetic and moral sense, or alternatively as the opposite of privation (the absence of necessary qualities in the universe). He warned against interpreting "positive" as being morally or aesthetically "good" (the greatest advantage and least disadvantage), as this includes negative characteristics. Instead, he suggested that "positive" should be interpreted as being perfect, or "purely good", without negative characteristics.[33]

Gödel's listed theorems follow from the axioms, so most criticisms of the theory focus on those axioms or the assumptions made. Oppy argued that Gödel gives no definition of "positive properties". He suggested that if these positive properties form a set, there is no reason to believe that any such set exists which is theologically interesting, or that there is only one set of positive properties which is theologically interesting.[32]

Modal versions of the ontological argument[edit]

Modal logic deals with the logic of possibility as well as necessity. Paul Oppenheimer and Edward N. Zalta note that, for Anselm's Proslogion chapter 2, "Many recent authors have interpreted this argument as a modal one." In the phrase 'that than which none greater can be conceived', the word 'can' could be construed as referring to a possibility. Nevertheless, the authors write that "the logic of the ontological argument itself doesn't include inferences based on this modality."[34] However, there have been newer, avowedly modal logic versions of the ontological argument, and on the application of this type of logic to the argument, James Franklin Harris writes:

[D]ifferent versions of the ontological argument, the so-called "modal" versions of the argument, which arguably avoid the part of Anselm's argument that "treats existence as a predicate," began to emerge. The [modal logic version] of these forms of defense of the ontological argument has been the most significant development.[35]

Hartshorne and Malcolm[edit]

Charles Hartshorne and Norman Malcolm are primarily responsible for introducing modal versions of the argument into the contemporary debate. Both claimed that Anselm had two versions of the ontological argument, the second of which was a modal logic version. According to James Harris, this version is represented by Malcolm thus:

If it [that than which nothing greater can be conceived] can be conceived at all it must exist. For no one who denies or doubts the existence of a being a greater than which is inconceivable, denies or doubts that if it did exist its nonexistence, either in reality or in the understanding, would be impossible. For otherwise it would not be a being a greater than which cannot be conceived. But as to whatever can be conceived but does not exist: if it were to exist its nonexistence either in reality or in the understanding would be possible. Therefore, if a being a greater than which cannot be conceived, can even be conceived, it must exist.

Hartshorne says that, for Anselm, "necessary existence is a superior manner of existence to ordinary, contingent existence and that ordinary, contingent existence is a defect." For Hartshorne, both Hume and Kant focused only upon whether what exists is greater than what does not exist. However, "Anselm's point is that what exists and cannot not exist is greater than that which exists and can not exist." This avoids the question of whether or not existence is a predicate.[36]

Referring to the two ontological arguments proposed by Anselm in Chapters 2 and 3 of his Proslogion, Malcolm supported Kant's criticism of Anselm's argument in Chapter 2: that existence cannot be a perfection of something. However, he identified what he sees as the second ontological argument in Chapter 3 which is not susceptible to such criticism.[37]

In Anselm's second argument, Malcolm identified two key points: first, that a being whose non-existence is logically impossible is greater than a being whose non-existence is logically possible, and second, that God is a being "than which a greater cannot be conceived". Malcolm supported that definition of God and suggested that it makes the proposition of God's existence a logically necessarily true statement (in the same way that "a square has four sides" is logically necessarily true).[37] Thus, while rejecting the idea of existence itself being a perfection, Malcolm argued that necessary existence is a perfection. This, he argued, proved the existence of an unsurpassably great necessary being.

Jordon Sobel writes that Malcolm is incorrect in assuming that the argument he is expounding is to be found entirely in Proslogion chapter 3. "Anselm intended in Proslogion III not an independent argument for the existence of God, but a continuation of the argument of Proslogion II."[38]

Alvin Plantinga[edit]

Alvin Plantinga criticized Malcolm's and Hartshorne's ontological arguments and proposed a variation of his own.

Christian Analytic philosopher Alvin Plantinga[39] criticized Malcolm's and Hartshorne's arguments, and offered an alternative. He argued that, if Malcolm does prove the necessary existence of the greatest possible being, it follows that there is a being which exists in all worlds whose greatness in some worlds is not surpassed. It does not, he argued, demonstrate that such a being has unsurpassed greatness in this world.[40]

In an attempt to resolve this problem, Plantinga differentiated between "greatness" and "excellence". A being's excellence in a particular world depends only on its properties in that world; a being's greatness depends on its properties in all worlds. Therefore, the greatest possible being must have maximal excellence in every possible world. Plantinga then restated Malcolm's argument, using the concept of "maximal greatness". He argued that it is possible for a being with maximal greatness to exist, so a being with maximal greatness exists in a possible world. If this is the case, then a being with maximal greatness exists in every world, and therefore in this world.[40]

The conclusion relies on a form of modal axiom S5, which states that if something is possibly true, then its possibility is necessary (it is possibly true in all worlds). Plantinga's version of S5 suggests that "To say that p is possibly necessarily true is to say that, with regard to one world, it is true at all worlds; but in that case it is true at all worlds, and so it is simply necessary."[41] A version of his argument is as follows:[5]

  1. A being has maximal excellence in a given possible world W if and only if it is omnipotent, omniscient and wholly good in W; and
  2. A being has maximal greatness if it has maximal excellence in every possible world.
  3. It is possible that there is a being that has maximal greatness. (Premise)
  4. Therefore, possibly, it is necessarily true that an omniscient, omnipotent, and perfectly good being exists.
  5. Therefore, (by axiom S5) it is necessarily true that an omniscient, omnipotent and perfectly good being exists.
  6. Therefore, an omniscient, omnipotent and perfectly good being exists.

Plantinga argued that, although the first premise is not rationally established, it is not contrary to reason. Michael Martin argued that, if certain components of perfection are contradictory, such as omnipotence and omniscience, then the first premise is contrary to reason. Martin also proposed parodies of the argument, suggesting that the existence of anything can be demonstrated with Plantinga's argument, provided it is defined as perfect or special in every possible world.[42]

Another Christian apologist, William Lane Craig, characterizes Plantinga's argument in a slightly different way:

  1. It is possible that a maximally great being exists.
  2. If it is possible that a maximally great being exists, then a maximally great being exists in some possible world.
  3. If a maximally great being exists in some possible world, then it exists in every possible world.
  4. If a maximally great being exists in every possible world, then it exists in the actual world.
  5. If a maximally great being exists in the actual world, then a maximally great being exists.
  6. Therefore, a maximally great being exists.

According to Craig, premises (2)–(5) are relatively uncontroversial among philosophers, but "the epistemic entertainability of premise (1) (or its denial) does not guarantee its metaphysical possibility."[43] Furthermore, Richard M. Gale argued that premise three, the "possibility premise", begs the question. He stated that one only has the epistemic right to accept the premise if one understands the nested modal operators, and that if one understands them within the system S5—without which the argument fails—then one understands that "possibly necessarily" is in essence the same as "necessarily".[44] Thus the premise begs the question because the conclusion is embedded within it. On S5 systems in general, James Garson writes that "the words ‘necessarily’ and ‘possibly’, have many different uses. So the acceptability of axioms for modal logic depends on which of these uses we have in mind."[45]

Sankara's dictum[edit]

An approach to supporting the possibility premise in Plantinga's version of the argument was attempted by Alexander R. Pruss. He started with the 8th – 9th-century AD Indian philosopher Sankara's dictum that if something is impossible, we cannot have a perception (even a non-veridical one) that it is the case. It follows that if we have a perception that p, then even though it might not be the case that p, it is at least the case that possibly p. If mystics in fact perceive the existence of a maximally great being, it follows that the existence of a maximally great being is at least possible.[46]

Automated reasoning[edit]

Paul Oppenheimer and Edward Zalta used an automated theorem prover—Prover9—to validate Anselm's ontological thesis. Prover9 subsequently discovered a simpler, formally valid (if not necessarily sound) ontological argument from a single non-logical premise.[47]

Christoph Benzmuller and Bruno Woltzenlogel Paleo used an automated theorem prover to validate Scott's version of Gödel's ontological argument. It has been shown by the same researchers that Gödel's ontological argument is inconsistent. However, Scott's version of Gödel's ontological argument is consistent and thus valid.

Criticisms and objections[edit]


One of the earliest recorded objections to Anselm's argument was raised by one of Anselm's contemporaries, Gaunilo of Marmoutiers. He invited his reader to conceive an island "more excellent" than any other island. He suggested that, according to Anselm's proof, this island must necessarily exist, as an island that exists would be more excellent.[48] Gaunilo's criticism does not explicitly demonstrate a flaw in Anselm's argument; rather, it argues that if Anselm's argument is sound, so are many other arguments of the same logical form, which cannot be accepted.[49] He offered a further criticism of Anselm's ontological argument, suggesting that the notion of God cannot be conceived, as Anselm had asserted. He argued that many theists would accept that God, by nature, cannot be fully comprehended. Therefore, if humans cannot fully conceive of God, the ontological argument cannot work.[50]

Defenders of Anselm have responded to Gaunilo's criticism by arguing that the argument applied only to concepts with necessary existence. He suggested that only a being with necessary existence can fulfill the remit of "that than which nothing greater can be conceived". Furthermore, a contingent object, such as an island, could always be improved and thus could never reach a state of perfection. For that reason, Anselm dismissed any argument that did not relate to a being with necessary existence.[48] While that response is not wrong, it is not decisive, since it invites a critic to retort that an Anselmian argument for the necessity of God's existence can be parodies by Gaunilo to show that the perfect island exists of necessity. [51] Indeed, once Anselm's formula is amended it follows that It is necessary that an island than which a greater island cannot be thought is in reality.

What is decisive is that Anselm himself remarked in Reply I that "something than which a greater cannot be thought cannot be thought not to exist, if it exists. Otherwise, it would not be something than which a greater cannot be thought, which is not logically consistent" [52] That remark is demonstrably true. [53] So, if it is legitimate to specify that Anselm's formula is true of some island, an island than which a greater island cannot be thought not only exists, it cannot be thought not to exist. But the premise Anselm invokes to prove that God exists is "Whatever is other than God can be thought not to exist". So Gaunilo's island both can and cannot be thought not to exist. Since that is impossible, it is not legitimate to specify that Anselm's formula is true of anything other than God.

That same applies to those objections which have tried to prove that Anselm's argument can be amended so that it entails that something than which nothing worse can be thought exists.

Thomas Aquinas[edit]

Thomas Aquinas, while proposing five proofs of God's existence in his Summa Theologica, objected to Anselm's argument. He suggested that people cannot know the nature of God and, therefore, cannot conceive of God in the way Anselm proposed.[54] The ontological argument would be meaningful only to someone who understands the essence of God completely. Aquinas reasoned that, as only God can completely know His essence, only He could use the argument.[55] His rejection of the ontological argument caused other Catholic theologians to also reject the argument.[56]

David Hume[edit]

David Hume reasoned that an ontological argument was not possible.

Scottish philosopher and empiricist David Hume argued that nothing can be proven to exist using only a priori reasoning.[57] In his Dialogues Concerning Natural Religion, the character Cleanthes proposes a criticism:

...there is an evident absurdity in pretending to demonstrate a matter of fact, or to prove it by any arguments a priori. Nothing is demonstrable, unless the contrary implies a contradiction. Nothing, that is distinctly conceivable, implies a contradiction. Whatever we conceive as existent, we can also conceive as non-existent. There is no being, therefore, whose non-existence implies a contradiction. Consequently there is no being, whose existence is demonstrable.[58]

Hume also suggested that, as we have no abstract idea of existence (apart from as part of our ideas of other objects), we cannot claim that the idea of God implies his existence. He suggested that any conception of God we may have, we can conceive either of existing or of not existing. He believed that existence is not a quality (or perfection), so a completely perfect being need not exist. Thus, he claimed that it is not a contradiction to deny God's existence.[57] Although this criticism is directed against a cosmological argument, similar to that of Samuel Clarke in his first Boyle Lecture, it has been applied to ontological arguments as well.[59]

Immanuel Kant[edit]

Immanuel Kant proposed that existence is not a predicate.

Immanuel Kant put forward an influential criticism of the ontological argument in his Critique of Pure Reason.[60] His criticism is primarily directed at Descartes, but also attacks Leibniz. It is shaped by his central distinction between analytic and synthetic propositions. In an analytic proposition, the predicate concept is contained in its subject concept; in a synthetic proposition, the predicate concept is not contained in its subject concept.

Kant questions the intelligibility of the concept of a necessary being. He considers examples of necessary propositions, such as "a triangle has three angles", and rejects the transfer of this logic to the existence of God. First, he argues that such necessary propositions are necessarily true only if such a being exists: If a triangle exists, it must have three angles. The necessary proposition, he argues, does not make the existence of a triangle necessary. Thus he argues that, if the proposition "X exists" is posited, it would follow that, if X exists, it exists necessarily; this does not mean that X exists in reality.[61] Second, he argues that contradictions arise only when the subject and predicate are maintained and, therefore, a judgement of non-existence cannot be a contradiction, as it denies the predicate.[60]

Kant then proposes that the statement "God exists" must be analytic or synthetic—the predicate must be inside or outside of the subject, respectively. If the proposition is analytic, as the ontological argument takes it to be, then the statement would be true only because of the meaning given to the words. Kant claims that this is merely a tautology and cannot say anything about reality. However, if the statement is synthetic, the ontological argument does not work, as the existence of God is not contained within the definition of God (and, as such, evidence for God would need to be found).[62]

Kant goes on to write, "'being' is evidently not a real predicate"[60] and cannot be part of the concept of something. He proposes that existence is not a predicate, or quality. This is because existence does not add to the essence of a being, but merely indicates its occurrence in reality. He states that by taking the subject of God with all its predicates and then asserting that God exists, "I add no new predicate to the conception of God". He argues that the ontological argument works only if existence is a predicate; if this is not so, he claims the ontological argument is invalidated, as it is then conceivable a completely perfect being doesn't exist.[21]

In addition, Kant claims that the concept of God is not of one a particular sense; rather, it is an "object of pure thought".[60] He asserts that God exists outside the realm of experience and nature. Because we cannot experience God through experience, Kant argues that it is impossible to know how we would verify God's existence. This is in contrast to material concepts, which can be verified by means of the senses.[63]

Douglas Gasking[edit]

Australian philosopher Douglas Gasking (1911–1994) developed a version of the ontological argument meant to prove God's non-existence. It was not intended to be serious; rather, its purpose was to illustrate the problems Gasking saw in the ontological argument.[64][65]

Gasking asserted that the creation of the world is the most marvellous achievement imaginable. The merit of such an achievement is the product of its quality and the creator's disability: the greater the disability of the creator, the more impressive the achievement. Non-existence, Gasking asserts, would be the greatest handicap. Therefore, if the universe is the product of an existent creator, we could conceive of a greater being—one which does not exist. A non-existent creator is greater than one which exists, so God does not exist.[65] Gasking's proposition that the greatest disability would be non-existence is a response to Anselm's assumption that existence is a predicate and perfection. Gasking uses this logic to assume that non-existence must be a disability.[64]

Oppy criticized the argument, viewing it as a weak parody of the ontological argument. He stated that, although it may be accepted that it would be a greater achievement for a non-existent creator to create something than a creator who exists, there is no reason to assume that a non-existent creator would be a greater being. He continued by arguing that there is no reason to view the creation of the world as "the most marvellous achievement imaginable". Finally, he stated that it may be inconceivable for a non-existent being to create anything at all.[5]

Coherence of a maximally great being[edit]

In his development of the ontological argument, Leibniz attempted to demonstrate the coherence of a supremely perfect being.[5] C. D. Broad countered that if two characteristics necessary for God's perfection are incompatible with a third, the notion of a supremely perfect being becomes incoherent. The ontological argument assumes the definition of God purported by classical theism: that God is omnipotent, omniscient, and morally perfect.[21] Kenneth Einar Himma claimed that omniscience and omnipotence may be incompatible: if God is omnipotent, then he should be able to create a being with free will; if he is omniscient, then he should know exactly what such a being will do (which may technically render them without free will). This analysis would render the ontological argument incoherent, as the characteristics required of a maximally great being cannot coexist in one being, thus such a being could not exist.[21]

Other criticisms[edit]

Bertrand Russell, during his early Hegelian phase, accepted the argument; he once exclaimed: "Great God in Boots!—the ontological argument is sound!"[66] However, he later criticized the argument, asserting that "the argument does not, to a modern mind, seem very convincing, but it is easier to feel convinced that it must be fallacious than it is to find out precisely where the fallacy lies." He drew a distinction between existence and essence, arguing that the essence of a person can be described and their existence still remain in question.[67]


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  2. ^ a b c d e Oppy 2007, pp. 1–2
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  7. ^ Craig, William Lane (2004). To everyone an answer: a case for the Christian worldview : essays in honor of Norman L. Geisler. InterVarsity Press. p. 124. ISBN 978-0-8308-2735-0.
  8. ^ Rowe, William L (2007). William L. Rowe on Philosophy of Religion: Selected Writings. Ashgate Publishing. p. 353. ISBN 978-0-7546-5558-9.
  9. ^ Dombrowski, Daniel A. (2005). Rethinking the ontological argument: a neoclassical theistic response. Cambridge University Press. p. 7. ISBN 978-0-521-86369-8.
  10. ^ McGrath, Alister (2011). Christian Theology: An Introduction. John Wiley and Sons. p. 34. ISBN 978-1-4443-9770-3.
  11. ^ Dawkins 2006, p. 80
  12. ^ Wainwright, William J. (2005). The Oxford handbook of philosophy of religion. Oxford University Press. p. 80. ISBN 978-0-19-513809-2.
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  20. ^ McGrath, Alister E. (1999). Science & religion: an introduction. Wiley-Blackwell. pp. 89–91. ISBN 978-0-631-20842-6.
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  22. ^ < Richard Campbell | Rethinking Anselm's Arguments, p. 34 | Brill 2018
  23. ^ < Richard Campbell | Rethinking Anselm's Arguments, p. 34 | Brill 2018
  24. ^ < Ian Logan | Reading Anselm's Proslogion | Ashgate 2009
  25. ^ < Ian Logan | Reading Anselm's Proslogion, p. 33
  26. ^ < Ian Logan | Reading Anselm's Proslogion | Ashgate 2009 | p.33
  27. ^ <{harvnb|Malcolm|1960|pp=41–62 >
  28. ^ < Ian Logan|Reading Anselm's Proslogion|Ashgate 2009 p. 34
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  35. ^ Harris, FH., Analytic Philosophy of Religion, Springer Science & Business Media, 2002, p. 105.
  36. ^ Harris, JF., Analytic Philosophy of Religion, Springer Science & Business Media, 2002, p. 109.
  37. ^ a b Malcolm 1960
  38. ^ Sobel, Jorden Howard (2004). Logic and theism: arguments for and against beliefs in God. Cambridge University Press. pp. 81–82. ISBN 978-0-521-82607-5.
  39. ^ "Evolution, Shibboleths, and Philosophers". The Chronicle of Higher Education. April 11, 2010. Retrieved 2010-04-28. Like any Christian (and indeed any theist), I believe that the world has been created by God, and hence "intelligently designed"
  40. ^ a b Plantinga 1998, pp. 65–71
  41. ^ Marenbon, M., Medieval Philosophy: An Historical and Philosophical Introduction, Routledge, 2006, p. 128.
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  43. ^ Craig, William Lane (2008). Reasonable faith. Crossway. p. 185. ISBN 978-1-4335-0115-9. Premises (2)–(5) of this argument are relatively uncontroversial. Most philosophers would agree that if God's existence is even possible, then he must exist. ... the epistemic entertainability of premise (1) (or its denial) does not guarantee its metaphysical possibility.
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  45. ^ Garson, James, Modal Logic, The Stanford Encyclopedia of Philosophy (Summer 2014 Edition), Edward N. Zalta (ed.).
  46. ^ Pruss, Alexander R. (2001). "Samkara's Principle and Two Ontomystical Arguments". International Journal for Philosophy of Religion. 49: 111–120. doi:10.1023/A:1017582721225.
  47. ^ Oppenheimer, Paul; Zalta, Edward N. (2011). "A Computationally-Discovered Simplification of the Ontological Argument". Australasian Journal of Philosophy. 89 (2): 333–349. doi:10.1080/00048401003674482.
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  49. ^ Cottingham, John (1986). Descartes. Blackwell Publishing. p. 62. ISBN 0-631-15046-3.
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  52. ^ <Ian Logan | Reading Anselm's Proslogion | Ashgate 2009, p. 70>
  53. ^ < Richard Campbell | Rethinking Anselm's Arguments | Brill 2018, ch. 6
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External links[edit]