A Successful Ontological Argument?
The ontological argument, roughly sketched, “purports to prove, simply from the concept of God as the supreme being, that God’s existence cannot rationally be doubted by anyone having such a concept of Him.”1
The ontological argument, by name, has a bad reputation. Skeptics who are familiar with it at least by name are immediately inclined to dismiss it, like Arthur Schopenhauer, as merely a “charming joke.” If you’re lucky enough to get a skeptic who is willing to go beyond even a chuckle, you’ll be hard pressed to find one who then won’t, almost instinctively, remind you of Kant’s and Hume’s infamous refutations (or, if nothing else, simply dropping their names is thought to do the trick). But this isn’t only a skeptic’s observation, but one common among many who’ve considered the argument. For example, a friend once approached me for some advice on how to counter an argument favored by one of her atheist friends. In response, I equipped her with Anselm’s version of the ontological argument, for it seemed to apply. But after I explained it to her, to my surprise, her face told me she was not only dissatisfied with it as a reply to her friend’s argument, but also personally unconvinced by the argument as such (and couldn’t tell me exactly why). Others have nonetheless found it to be of great value—among which include such profound thinkers as Aquinas, Descartes and Leibniz; and contemporarily, Charles Hartshorne, Norman Malcom, and Alvin Plantinga. In lieu of it’s controversial history, the reason for the argument’s sharp division between defenders and detractors remains unsettled. For almost everyone who has written on it has “noted that the argument has about it an air of egregious unsoundness or perhaps even trumpery and deceit; yet it is profoundly difficult to say exactly where it goes wrong.”2
Despite such a bad reputation, some of the contemporary versions of the ontological argument are considered to be sound. Perhaps the most famous of these is Plantinga’s version. Plantinga has greatly devoted himself to studying this argument, and in so doing has come out with his own form that utilizes possible world semantics. Possible world semantics is a syntax used in modal logic to illustrate modal concepts. It is helpful in illuminating the realm of possibility in the metaphysical sense (what could actually be the case given a certain logical state of affairs within a ‘world’ unlike our own). So a ‘world’ can be defined as “a maximal description of reality or a way reality might be.”3 The main thing to understand is that there can be an infinite number of possible worlds, each of which containing a different logical state of affairs (i.e. possibilities), but none of which contain logical contradictions (i.e. there can be no possible world in which a logically impossible state of affairs obtains—such as a possible world in which the proposition “cows both exist and do not exist” is true). Philosopher William Lane Craig describes it this way:
Plantinga’s Ontological Argument
A Simpler Version of Plantinga’s Argument
Plantinga has stated his ontological argument several different ways, some more detailed than others. One of the simpler versions is as follows:
An Even Simpler Version of Plantinga’s Argument
William Lane Craig has offered yet a simpler statement of Plantinga’s argument, one that I’ve found to be quite helpful:
Has Plantinga given us some insight as to how a sound version of the ontological argument might look? Some critics say not. For are not these arguments guilty of begging the question? Presumably we would not believe the key premise in each argument (I have put an asterisk before the number of the key premise in each argument), namely that “it is possible that a maximally great being exists” unless we already thought the conclusion “a maximally great being exists” is true. In other words, we can’t use as a premise in our argument what the argument is trying to establish. But are these arguments guilty of begging the question? A closer look indicates they are not. If you recall, as the possible worlds semantics are used in arguments, we are considering metaphysical possibility. Bearing this in mind it becomes clear that what the key premises entail is quite different from what the conclusion entails. For the insight behind the premises under consideration is not whether it is possible that a maximally great being actually exists, but whether the intuitive notion of a maximally great being is a logically coherent one—for if it isn’t, it cannot possibly exist in some world.
So do we finally have a sound ontological argument? The above arguments are, without question, logically valid. So in order to determine their soundness, the question remains as to what reasons we have for thinking the key premise in each argument is true. To that effect, no one has yet been able to show the idea of a maximally great being incoherent. The great J. L. Mackie tried, but failed.10 Others have since done likewise (Flew and Kai Nielson come to mind). The burden here is obviously on one who wishes to show the idea of God, namely the attributes entailed in the property maximal excellence (omnipotence, omniscience, and moral perfection), internally inconsistent or incoherent. But this is yet to be done. Still some will insist that the argument fails because we cannot know a priori whether each key premise is true. But this objection is weak, if it is to be considered an objection at all. That we cannot know a priori each key premise is true is debatable, on top of the fact that knowing a priori the truth of a proposition is certainly not a good criterion for determining a proposition's rational acceptability. Moreover, even if we didn’t have a way of knowing a priori the truth of the key premises, we could establish them on the basis of a posteriori considerations, at which point we may simply turn to some of the other classical arguments for the existence of God.
Thus, I am convinced that Plantinga has given us a sound ontological argument after all. But for the sake of natural theology, we should, pace Anselm, at least temporarily rename the ontological argument in hopes of restoring its academic respectability.
__________________________________________________________
The ontological argument, by name, has a bad reputation. Skeptics who are familiar with it at least by name are immediately inclined to dismiss it, like Arthur Schopenhauer, as merely a “charming joke.” If you’re lucky enough to get a skeptic who is willing to go beyond even a chuckle, you’ll be hard pressed to find one who then won’t, almost instinctively, remind you of Kant’s and Hume’s infamous refutations (or, if nothing else, simply dropping their names is thought to do the trick). But this isn’t only a skeptic’s observation, but one common among many who’ve considered the argument. For example, a friend once approached me for some advice on how to counter an argument favored by one of her atheist friends. In response, I equipped her with Anselm’s version of the ontological argument, for it seemed to apply. But after I explained it to her, to my surprise, her face told me she was not only dissatisfied with it as a reply to her friend’s argument, but also personally unconvinced by the argument as such (and couldn’t tell me exactly why). Others have nonetheless found it to be of great value—among which include such profound thinkers as Aquinas, Descartes and Leibniz; and contemporarily, Charles Hartshorne, Norman Malcom, and Alvin Plantinga. In lieu of it’s controversial history, the reason for the argument’s sharp division between defenders and detractors remains unsettled. For almost everyone who has written on it has “noted that the argument has about it an air of egregious unsoundness or perhaps even trumpery and deceit; yet it is profoundly difficult to say exactly where it goes wrong.”2
Despite such a bad reputation, some of the contemporary versions of the ontological argument are considered to be sound. Perhaps the most famous of these is Plantinga’s version. Plantinga has greatly devoted himself to studying this argument, and in so doing has come out with his own form that utilizes possible world semantics. Possible world semantics is a syntax used in modal logic to illustrate modal concepts. It is helpful in illuminating the realm of possibility in the metaphysical sense (what could actually be the case given a certain logical state of affairs within a ‘world’ unlike our own). So a ‘world’ can be defined as “a maximal description of reality or a way reality might be.”3 The main thing to understand is that there can be an infinite number of possible worlds, each of which containing a different logical state of affairs (i.e. possibilities), but none of which contain logical contradictions (i.e. there can be no possible world in which a logically impossible state of affairs obtains—such as a possible world in which the proposition “cows both exist and do not exist” is true). Philosopher William Lane Craig describes it this way:
Perhaps the best way to think of a possible world is a huge conjunction p & q & r & s . . . (“&” means “and”), whose individual conjuncts are the propositions p, q, r, s, . . . A possible world is a conjunction which compromises every proposition or its contradictory, so that it yields a maximal description of reality—nothing is left out of such a description. By negating different conjuncts in a maximal description (“-” means “it is not the case that”), we arrive at different possible worlds:With that in mind, some definitions are in order to get the full gist of Plantinga’s ontological argument. In his argument, the distinction between greatness and excellence is crucial. Plantinga states “we might say that the excellence of a being in a given world W depends only upon its (non world-indexed) properties in W, which its greatness in W depends not merely upon its excellence in W, but also upon its excellence in other worlds.”5
W1: p & q & r & s . . .
W2: p & -q & r & -s . . .
W3: -p & -q & r & s . . .
W4: p & q & -r & s . . .
Only one of these descriptions will be composed of conjuncts all of which are true and so will be the way reality actually is, that is to say, the actual world.4
Plantinga’s Ontological Argument
(1) There is a world W in which there exists a being with maximal greatness.
(2) A being has maximal greatness in a world only if it exists in every possible world.
(3) The property has maximal greatness entails6 the property has maximal excellence in every possible world.
(4) Maximal excellence entails omniscience, omnipotence, and moral perfection.
*(5) Maximal greatness is possibly exemplified.
But for any property P, if P is possibly exemplified, then there is a world W and an essence E such that E is exemplified in W, and E entails has P in W. So
(6) There is a world W* and an essence E* such that E* is exemplified in W* and E* entails has maximal greatness in W*.
If W* had been actual, therefore, E* would have been exemplified by an object that had maximal greatness and hence (by (3)) had maximal excellence in every possible world. So if W* had been actual, E* would have been exemplified by a being that for any world W had the property has maximal excellence in W. But every world-indexed property of an object is entailed by its essence. Hence if W* had been actual, E* would have entailed, for every world W, the property has maximal excellence in every possible world. That is, if W* had been actual, the proposition
(7) For any object x, if x exemplifies E*, then x exemplifies the property has maximal excellence in every possible world
would have been necessarily true. But what is necessarily true does not vary from world to world. Hence (7) is necessary in every world and is therefore necessary. So
(8) E* entails the property has maximal excellence in every possible world.
Now a being has a property in a world W only if it exists in that world. So E* entails the property exist in every possible world. E* is exemplified in W*; hence if W* had been actual, E* would have been exemplified by something that existed and exemplified it in every possible world. Hence
(9) If W* had been actual, it would have been impossible that E* fail to be exemplified.
But again, what is impossible does not vary form world to world hence, it is in fact impossible that E* fail to be exemplified; so E* is exemplified; so
(10) There exists a being that has maximal excellence in every world.
That is, there actually exists a being that is omniscient, omnipotent, and morally perfect and that exists and has these properties is every possible world. This being is God.7
A Simpler Version of Plantinga’s Argument
Plantinga has stated his ontological argument several different ways, some more detailed than others. One of the simpler versions is as follows:
(1) It is possible that there be a being that has maximal greatness.
(2) So there is a possible being that in some world W has maximal greatness.
(3) A being has maximal greatness in a given world only if it has maximal excellence in every world.
(4) A being has maximal excellence in a given world only if it has omniscience, omnipotence, and moral perfection in that world.
*(5) There is a possible world in which maximal greatness is instantiated.
And the analogues of (3) and (4) spell out what is involved in maximal greatness:
(6) Necessarily, a being is maximally great only if it has maximal excellence in every world
and
(7) Necessarily, a being has maximal excellence in every world only if it has omniscience, omnipotence, and moral perfection in every world.
But if (5) is true, then there is a possible world W such that if it had been actual, then there would have existed a being that was omnipotence, omniscient, and morally perfect; this being, furthermore, would have had these qualities in every possible world. So it follows that if W had been actual, it would have been impossible that there be no such being. That is, if W had been actual
(8) There is no omnipotence, omniscient, and morally perfect being
would have been an impossible proposition. But if a proposition is impossible in at least one possible world, then it is impossible in every possible world; what is impossible does not vary from world to world. Accordingly, (8) is impossible in the actual world, i.e., impossible simpliciter. But if it is impossible that there be no such being, then there actually exists a being that is omnipotent, omniscient, and morally perfect; this being, furthermore, has these qualities essentially and exists in every possible world.8
An Even Simpler Version of Plantinga’s Argument
William Lane Craig has offered yet a simpler statement of Plantinga’s argument, one that I’ve found to be quite helpful:
*(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.9
Has Plantinga given us some insight as to how a sound version of the ontological argument might look? Some critics say not. For are not these arguments guilty of begging the question? Presumably we would not believe the key premise in each argument (I have put an asterisk before the number of the key premise in each argument), namely that “it is possible that a maximally great being exists” unless we already thought the conclusion “a maximally great being exists” is true. In other words, we can’t use as a premise in our argument what the argument is trying to establish. But are these arguments guilty of begging the question? A closer look indicates they are not. If you recall, as the possible worlds semantics are used in arguments, we are considering metaphysical possibility. Bearing this in mind it becomes clear that what the key premises entail is quite different from what the conclusion entails. For the insight behind the premises under consideration is not whether it is possible that a maximally great being actually exists, but whether the intuitive notion of a maximally great being is a logically coherent one—for if it isn’t, it cannot possibly exist in some world.
So do we finally have a sound ontological argument? The above arguments are, without question, logically valid. So in order to determine their soundness, the question remains as to what reasons we have for thinking the key premise in each argument is true. To that effect, no one has yet been able to show the idea of a maximally great being incoherent. The great J. L. Mackie tried, but failed.10 Others have since done likewise (Flew and Kai Nielson come to mind). The burden here is obviously on one who wishes to show the idea of God, namely the attributes entailed in the property maximal excellence (omnipotence, omniscience, and moral perfection), internally inconsistent or incoherent. But this is yet to be done. Still some will insist that the argument fails because we cannot know a priori whether each key premise is true. But this objection is weak, if it is to be considered an objection at all. That we cannot know a priori each key premise is true is debatable, on top of the fact that knowing a priori the truth of a proposition is certainly not a good criterion for determining a proposition's rational acceptability. Moreover, even if we didn’t have a way of knowing a priori the truth of the key premises, we could establish them on the basis of a posteriori considerations, at which point we may simply turn to some of the other classical arguments for the existence of God.
Thus, I am convinced that Plantinga has given us a sound ontological argument after all. But for the sake of natural theology, we should, pace Anselm, at least temporarily rename the ontological argument in hopes of restoring its academic respectability.
__________________________________________________________
- Richard Taylor, in the introduction of The Ontological Argument (Doubleday 1965), vii.
- Alvin Plantinga, ‘The Ontological Argument’, in Philosophy of Religion (Rutgers University Press, 2002), p. 180. A reprint from ‘God and Necessity’, The Nature of Necessity (Oxford: Clarendon Press, 1974), pp. 196-221.
- J. P. Moreland and William Lane Craig, Philosophical Foundations for a Christian Worldview (IL: InterVarsity Press, 2003), p. 50.
- William Lane Craig, “The Ontological Argument,” in To Everyone An Answer (InterVarsity Press, Downers Grove, IL: 2004), p. 126.
- Alvin Plantinga, ‘The Ontological Argument’, in Philosophy of Religion (Rutgers University Press, 2002), p. 182.
- Where, we recall, a property P entails a property Q if there is no world in which there exists an object x that has P but lacks Q.
- Alvin Plantinga, ‘The Ontological Argument’, in Philosophy of Religion (Rutgers University Press, 2002), p. 181, 183-184.
- Alvin Plantinga, God, Freedom, and Evil (Eerdmans Publishing Co., MI: 1986), pp. 108, 111-112.
- William Lane Craig, “The Ontological Argument,” in To Everyone An Answer (InterVarsity Press, Downers Grove, IL: 2004), p. 128.
- J. L. Mackie, “Evil and Omnipotence,” in The Philosophy of Religion, ed. Basil Mitchell (London: Oxford University Press, 1971), pp. 92-93. One response to Mackie, among many, can be found in Alvin Plantinga, God, Freedom, and Evil (Eerdmans Publishing Co., MI: 1986), pp. 12-24.
posted by Chad at 11:54 PM
3 Comments:
This is a great post, well written and well put together. Thank you for taking the time to do this.
emily
If you want a thorough, clear and concise summary of reasons why the modal ontological argument has not won widespread assent, you should read Peter van Inwagen's articles "Ontological Arguments" and "Modal Skepticism." Van Inwagen, by the way, is a colleague of Plantinga's at Notre Dame (where I am a grad student in philosophy), and moreover, he is a theist.
Van Inwagen would reject the burden of proof move that you make in favor of the ontological argument, and I have to agree with him. There isn't anything on the side of the theistic supposition other than a whole lot of history, which is most likely irrelevant to the argument itself.
Of course, I think that the ontological argument is sound (since I am a theist, and actuality implies possibility), but the ontological argument will not convince anyone unconvinced of the possibility of a maximally-great being.
Thank you, Alex, for you comment!
"If you want a thorough, clear and concise summary of reasons why the modal ontological argument has not won widespread assent, you should read Peter van Inwagen's articles "Ontological Arguments" and "Modal Skepticism." Van Inwagen, by the way, is a colleague of Plantinga's at Notre Dame (where I am a grad student in philosophy), and moreover, he is a theist."
I am familiar with Van Inwagen, thought not as familiar as I am with Plantinga. Most of what I’ve read of his (Inwagen) I’ve been either unsettled on or in sharp disagreement (but perhaps this claim is made in ignorance) with.
"Van Inwagen would reject the burden of proof move that you make in favor of the ontological argument, and I have to agree with him. There isn't anything on the side of the theistic supposition other than a whole lot of history, which is most likely irrelevant to the argument itself."
I don’t see how one who wants to criticize the main premise can avert the burden of proof. For it demands showing the idea of a maximally great being internally incoherent, which at least doesn’t appear to be prima facie. Because the property of maximal excellence (or the conjunction of any other of the divine attributes) doesn’t present itself as conspicuous in any obvious way, I think it’s reasonable to say the burden of proof is on the one who thinks so. If what I’m saying is wrong, however, who, if anyone, would bear the burden of proof with respect to the argument’s main premise then?
"Of course, I think that the ontological argument is sound (since I am a theist, and actuality implies possibility), but the ontological argument will not convince anyone unconvinced of the possibility of a maximally-great being."
It would be silly to say the main premise cannot be rationally denied. So if that’s what you mean, I agree. Skeptics are free to reject this premise without appearing unwarranted for the rejection. But again, this just brings us back to Nielson’s argument and variants thereof, none of which have proven either philosophically successful or academically popular.
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