Sunday, March 30, 2008

Plantinga's Argument for the Existence of God

The Reformed community widely differs on the acceptability of the “natural” proofs for God’s existence. However, Alvin Plantinga has reformulated St. Anselm’s classical ontological proof for the existence of God. The consistency of the argument is rather convincing. St. Anselm’s traditional formulation, which is a reduction ad absurdum argument, is as follows:

  1. God exists in the understanding but not in reality.
  2. Existence in reality is greater than existence in the understanding alone.
  3. God’s existence in reality is conceivable.
  4. If God did exist in reality, then he would be greater than he is (from 1. & 2.).
  5. It is conceivable that there be a being greater than God is (3 & 4).
  6. It is conceivable that there be a being greater than the being than which nothing greater can be conceived (5., by the definition of ‘God’).

But Surely

  1. It is false that it is conceivable that there be a being greater than the being than which none greater can be conceived.

Since 6. and 7. contradict each other, we may conclude that

  1. It is false that God exists in the understanding but not in reality.

So if God exists in the understanding, he also exists in reality. [1]

Thus, step 1 is the proposition “to be reduced to absurdity.” Steps 2, 3, and 7 are premises in the argument of which step 2 poses the only real problem. That is, is it necessarily true that “existence in reality is greater than existence in the understanding alone?” What is St. Anselm comparing at this point? He is comparing something that exists with something that does not exist and then predicating that that which exists is by default greater than which was does not. However, are existent and non-existent terms comparable terms? No, St. Anselm is comparing unlike terms. Even more, there is a sense in which the term “existent thing” is valid and the so-called term “non-existent thing” is absurd, for it is really nothing. Also, does St. Anselm’s argument account for the supreme excellence of God in all possible worlds? That is, can it be predicated of God that a necessary attribute of his is supreme excellence, thus it is true in every possible (or hypothetical) world? Rather, St. Anselm’s argument does not leave itself open to this analysis since his argument directly deals with the actual world.

However, Plantinga reformulates the argument and remedies these inconsistencies. First, it is important to understand that “those who worship God do not think of him as a being that happens to be of surpassing excellence in this world but who in some other worlds is powerless or uninformed or of dubious moral character.” Thus, if P is a property of an individual, then it can be stated that, “P is a universal property if and only if P is instantiated in every world or no world.” Therefore, unlike St. Anselm’s postulate, “Existence and necessary existence are not themselves perfections, but necessary conditions of perfection.”[2] That is, existence in both this world and all possible worlds do not constitute perfection. However, if we are arguing for the existence of an all perfect being, then one thing that must be true of this perfect being is that his essence or properties are necessarily the same in all possible worlds – thus contributing to his perfection. This can be stated as follows:

  1. The property has maximal greatness entails the property has maximal excellence in every possible world.
  2. Maximal excellence entails omniscience, omnipotence, and moral perfection.
  3. Maximal greatness is possibly exemplified.

Thus, if the property maximal greatness is possibly exemplified in any world, then it is necessarily follows that it is exemplified in all world by the mere definition of maximal greatness including or entails maximal excellence. Therefore, the ontological argument can be restated as follows:

  1. God exists in a conceivable world but not in reality.
  2. It is conceivable that God exists in a world W and as a perfect being has an essence E such that E is exemplified in W and E entails has maximal greatness in W.
  3. Maximal greatness necessarily exemplifies the property has maximal excellence in every possible world.
  4. Therefore, God’s essence entails has maximal excellence in every possible world.
  5. If world W had been actual, it would have been impossible that essence E fail to be exemplified given its necessary nature.
  6. Therefore, there exists a being that has maximal excellence in every world.
In simpler terms:

1. Define God: God is that than which no greater can be conceived.

2. It is greater to exist not only in the mind or in the imagination but also independently of the imagination (i.e. in reality) than to exist only in the imagination.

3. It is possible to conceive of that than which no greater can be conceived.

4. It is possible to conceive of God existing not only in the mind but also in reality.

5. If God exists only in the imagination but not in reality then (because of 2.) it is possible to conceive of a being greater than that than which no greater can be conceived.

6. Number 5 self-contradicts.

7. Therefore, the protasis of 5. must be false (i.e. God exist only in the imagination.)

8. Therefore, God exists not only in the mind but also in reality.


Plantinga’s ontological argument was much more cogent and convincing than his disappointing Free Will Defense. The argument definitely required at least a cursory knowledge of logic and valid syllogisms. All in all, it was an intellectually rigorous work, but well worth the read. The one point at which I believe an atheist or atheologian could respond is in questioning the premises. The reasoning is valid, but the axioms utilized to establish the validity of the conclusion would undoubtedly be attacked by contrary thinkers, albeit, it is an unjustified attack given the cogency of the argument.

I would recommend both of these arguments to be read by believers. The Free Will Defense can aid the Reformed thinker in flushing out his own beliefs about God’s sovereignty and the means by which free agents both act/move and are culpable for their actions. Plantinga’s ontological argument is a good example of right reason and logic applied to the things of God in a cogently conclusive manner.

However, I would not recommend the Free Will Defense to unbelievers or for any use in an apologetic discourse. As noted above, it is fraught with too many perils. However, if you can get an unbeliever to actually go through the ontological argument with you, I believe it can serve to show forth the rationality and coherence that is Christianity.

[1] Plantinga, 198.

[2] Ibid, 214.


  1. There's something still unsatisfying about what I'm about to point out, but in philosophy circles Plantinga's free will defense argument (along with those of a few other folks) is generally considered a slam dunk. Think about this for just a moment: philosophers, who cannot agree on anything (including whether there are really tables there when we think we see tables), agree (pretty much) that the classic argument from evil against God's existence is a non-starter. They don't use it any more. It is dead, as far as legitimacy among philosophers is concerned. And it is dead b/c Plantinga killed it.

    Now, here's the part that is still unsatisfying. I have the same concerns you do, more or less, about Plantinga's approach. Especially because Plantinga calls himself and is known as a "Reformed philosopher," it is kind odd that he would advocate an incompatiblist (libertarian) notion of free will. And, make no mistake, Plantinga openly admits to being an Arminian. (He said to me once that he is a "Calvinist who thinks that Dordt went the wrong way") He envisions Arminianism as being an acceptable subgroup within Reformed theology. In any case, this is what he says to real Calvinists like you and me: you don't have to believe in (his kind of) free will in order to use his free will defense argument. The point of the argument is simply this: there is a logically possible world (I hate that way of speaking, by the way) in which God is omnipotent, omniscient, and evil happens. Those three things are NOT incompatible, and thus the classic argument from evil is invalid (and, thus, dead). The way Plantinga shows that they are incompatible is by positing free will: if we imagine a world in which God gives creatures (libertarian) free will, then in that world God would clearly be all good, all powerful, but evil could still take place. But, Plantinga, says, you don't actually have to believe in libertarian free will. You can be a traditional Calvinist and deny it, but still use it to show that the atheist's argument is not valid.

    Like I said, there's something unsatisfying about that. But just some further thoughts from the horse's mouth, as they say.

  2. Great comment....

    The free will defense really is a very poor defense that is easy to sell to most people. Its greatest weakness is the implications that it has on the realm of Theology Proper – i.e the character of God.

    If we explain the origin of sin comes through man freely choosing sin because man is only accountable for that which he chooses and acts upon freely, then this also predicates the possibility or ability to sin on God’s part. That is, in this view man is pictured as a being that is able to choose either good or evil and this is what makes his decisions culpable. Responsibility for an action is only possible if the individual had the opportunity or possibility to also NOT choose that action. However, is God culpable for his decisions? Absolutely!! However, does God have the ability to sin, or will there ever be the possibility of God sinning? Absolutely NOT!! So, God does righteous actions without the possibility of him doing the opposite (i.e. sinning).

    So the free will defense falls apart. A being does not need to have the ability to either choose good or evil for the being to be culpable for his actions.

  3. Jason, again I agree with you more or less concerning your "implicational" critique of the Free Will Defense. And thanks for your kind comment on my earlier comment. :-)

    I'm just trying to point out, though, that Plantinga really has done something quite remarkable in the philosophical world, which operates according to certain rules. Under those rules, Plantinga still was able to drag the argument from evil against God's existence (in its deductive form: versions with inductive form remain in use) out into the street and shoot it in the head.

    Under the "rules" of academic philosophy, your argument against the Free Will Defense doesn't fly. Again, remember that I agree with you. But in 'academic' circles, you can't criticize the free will defense b/c of some alleged consequence it has for the doctrine of God. The point is, does it still allow God to be omniscient, omnipotent (in something close to the traditional idea of those concepts), even though evil exists? If it does, then it works as a defense against the atheistic arg from evil. All you have to do to refute a deductive argument is provide a logically-possible counterexample, which the FWD succeeds at doing. The fact that 'hard core' Calvinists like you and I don't like some of the implications of that counterexample doesn't matter.

    We can keep Plantinga from being licensed to teach in our presbyteries if we want (which we should), but we have to acknowledge the validity of his defense in logical terms. Those logical terms are the "rules of the game."

    I hope that makes sense.

  4. Xon,

    I absolutely agree with you 100%. And really, that is why I love Plantinga's writings, and also much of Ravi Z's also. While I do not like the theological implications of several of their lines of argumentation, within the academic world, these men take academicians to task, answering almost all objections and leaving opponents with a feeling of "What just happened?!?!" The short and skinny is, these guys, and particularly Plantinga, are invaluable servants in God's kingdom.

    My concerns with the free will defense would only be raised in an evangelistic context - i.e. I would not use or I would show the inadequacies of it because of its implications for Theology Proper....

    The next work(s) I want to tackle by Plantinga or his three part series on Warrant.

  5. Cool, Jason.

    The Warrant stuff will let you discuss his "Evolutionary Argument against Naturalism." There is an entire book of naturalist responses to that essay (Again, that's just the stick Plantinga carries in the academic world).

    Also, his "Reformed epistemology" stuff is very interesting, which is what the Warrant stuff really is a further development of. Also, his Presidential Address to the American Philosophical Association, from sometime in the early 80s, called "How to be an Anti-Realist", is top notch. (His argument in a nutshell: to be an Anti-Realist, you have to be a theist!)

    Then, if you're really ready to blow your mind, you should try to digest some of James Ross' stuff (he's at UPenn) on freedom and analytic philosophy. Ross is a medievalist, really, who takes Plantinga (and analytic philosophy) to task in a number of places. But, Ross also talks about freedom in a way that is perfectly consistent with Calvinism. He recognizes Aquinas as a "determinist," of sorts.

  6. Your argument is interesting, but there are several parts that you've passed over that are not logical.

    First of all, your definition of "greater" is hazy at best. This axis that you use to define something as "greater" than anything else is completely subjective. Why must things that exist be "greater" that those that don't? After all, something that has many contradictory aspects and characteristics seems much greater than the things that must conform to the boundaries of reality.

    But beyond semantics, there are still problems. In Plantinga's original argument, there is the comparison of that which exists with that which does not. You address this with the modified argument, but this is flawed.

    You say that when someone says that they believe in God, they believe not just that he exists in this world but that he exists in all possible worlds. Then you compare this "possible" world to the real world in the same way that the previous argument compared that which exists with that which does not. But there are two problems with this: When someone says they believe that God exists, it is not necessary that he exist in all possible worlds, merely that he exists in all worlds that exist. It doesn't matter to the believer whether there is a "possible" world that he doesn't exist in. All that matters is that all the worlds that do exist have God in them.

    But even if we allow this, there is still the problem of comparing that which exists to that which does not. Or rather, that which only "might" exist, because of course we can never be sure that there are any other worlds beyond our own (And i speak of course of universes when i say "worlds," i am not referring to other planets). First you have to prove that other possible worlds even exist, and even then, you've still got a very large problem.

    This last problem is subtle, and not easy to catch. At the end of your argument, the pivotal point fails. You say that if God exists, he must be greater than that which nothing greater can be conceived, since he exists, and is therefore greater than the version of himself that exists only in thought. You say it is conceivable that such a being exists, and call this a contradiction: how can it be conceivable that there is a being that is greater than that which no greater can be conceived?

    But here's the problem with that: there's no contradiction. It is conceivable that such a being exists. Just because it itself is not conceivable does not mean that the idea that it exists is not conceivable. They are two very different things, the idea of such a being existing, and the idea of such a being itself. One can be conceivable and the other not with no contradiction, similar to how infinity is conceived of: no one can comprehend the concept of infinity, because it is, by definition, infinite. But that does not mean that no one can comprehend the supposition that an infinite distance exists.

    I'm not going to end on a condescending note about how you should deconvert to atheism, or anything tacky like that.Suffice it to say, these are the kinds of reasons I'm an Atheist. To paraphrase an Atheist whose ideas fall very much in line with my own: "I'm not saying what i do believe. I'm not saying that I have this clear understanding of how it all fits together. I just know, that ain't it."

    Happy to hear replies and responses.


    Dee Emarr


Before posting please read our Comment Policy here.

Think hard about this: the world is watching!