The Ontological Argument in Plain English

The ontological argument attempts to make the statement "There is no God", or more accurately, "God is imaginary", logically incoherent. Rather than look at it in a syllogistic form, let's take a peak at it in colloquial English.

The word "God" here means the Creator of everything that exists, and by extension the greatest conceivable being. Great means "more unusual or considerable in degree, intensity, scope, etc".

So start with the statement:

• God is just in your mind (i.e., he has no extramental existence; he is imaginary)

 Let's replace the word "God" with what it means:

• [The greatest conceivable being] is just in your mind

But if something exists just in your mind, then there is a version of that thing that is greater, i.e., more unusual or considerable in degree, intensity, scope, etc. Namely, one that exists in reality as well.

Consider an imaginary vs a real elephant. Which one is more unusual or considerable in degree, intensity, scope, etc? The real one exists in your mind as well (when you think about it), but it also exists out there in reality. So it has what the first one has plus more. So existence in reality + mind is more unusual or considerable in degree, intensity, and scope than existence in just the mind.

So let's compare two greatest conceivable beings:

• [The greatest conceivable being] is just in your mind

• [The greatest conceivable being] is in your mind and also reality

The second one is more unusual or considerable in degree, intensity, and scope than the first. So the first one is not the greatest conceivable being. So the sentence "God is imaginary" really means:

• [The greatest conceivable being] is [not the greatest conceivable being]

This is clearly a logical contradiction. Something cannot be both P and not-P. So the statement:

• God is imaginary

...is logically incoherent. Which means that it's negation is necessarily true:

• It is not the case that God is imaginary

Or, to put it another way:

• God exists

Or so goes the argument. I leave it for readers to decide on their own whether this is a good argument or not. :)

Alvin Plantinga's Modal Ontological Argument

I. Possibility, Necessity, and Impossibility

Possible: In this argument, "possible" means "logically possible." As long as there are no contradictions in a thing or idea, then it is logically possible, even if not actually true. It is logically possible that people can fly like Superman. There are at least no prima facie contradictions in that idea (since there are several movies clearly depicting it), and if someone claimed that there were, the burden would be on them to provide an argument. Therefore, "flying like Superman" is false, but still possible.

Necessity: Logically necessary. "No bachelors are married" is a necessary truth. It can't logically be false. Many philosophers of mathematics think that numbers actually exist. If so, they too are necessary. It is impossible for the number 3 to not exist.

Impossible: Logically impossible. The opposite of logically necessary. It is logically impossible that there are triangles with four sides. It is not logically impossible that a human can live without a head, even though such a thing is physically impossible.

II. Possible Worlds

Think of these as simulations of alternate realities. Ways that reality could be, one of which matches the actual world. These are conceptual tools used to describe what is (logically) possible, impossible, and necessary. So when we say something is logically possible, what we mean is that such a thing exists in some possible world, even if it doesn't exist in the actual world. And if something is logically necessary, then it exists in all possible worlds, including the actual world.

• For example, since there doesn't seem to be any logical incoherence in the idea of Superman, then we would say that Superman is logically possible and so he exists in some possible world. Clearly, he doesn't actually exist in the real world, however.
• That all bachelors are unmarried is a necessary truth, and so is true in all possible worlds. If numbers actually exist, then the number 3 is a necessary being and exists in all possible worlds. There is no possible world that has the numbers 1, 2, 4, 5 and so on, without the number 3.

III. A Maximally Great Being

The word "God" is often used as a code word for the creator of everything other than himself, and thus who is greater than anything else. There is nothing else greater than the Maximally Great Being, by definition. One property the MGB would have is necessary existence, and not possible existence. If it only had possible existence, then it would exist in some possible worlds and not others. But if could exist or not exist, then it would depend on something else for its existence (parents, for example), and thus would not be what it is by definition: the Maximally Great being. Or another way to think of it is that if it is the Creator of everything other than itself, and since every possible world contains something, then it would have to exist in every possible world.

IV. Premise 1: It is logically possible that the MGB exists

That is to say, it is not logically incoherent. This is for the sake of argument. Perhaps such a thing is logically incoherent, but go with it for now that there are no logical contradictions in the idea. That doesn't mean it actually exists, just that it is logically possible. You can accept that Superman is logically coherent without actually accepting that he exists. Do the same here for now.

V. Premise 2: If it is logically possible that the MGB exists, then MGB exists in some possible world

Remember what "possible" means, in section II above. If the MGB is logically coherent, then it is possible and thus exists in at least one of the simulations of alternate realities (possible worlds).

VI. Premise 3: If the MGB exists in some possible world, then the MGB exists in all possible worlds

Since as noted in section III, the MGB is a necessary being. If it were only a possible being, then it would not be maximally great. And as noted in section II, saying that something is necessary means that it exists in all possible worlds.

V. If the MGB exists in all possible worlds, then the MGB exists in the real world

Since the real world is one of the possible worlds. The conclusion is therefore that the MGB, or what some might label "God", actually exists.

VI. Does this actually prove God's existence?

Nope! What it does seem to do, however, is prove that if the MGB is not logically incoherent, then it follows that it must exist. In other words, the probability of the existence of the MGB is either 0%, or 100%. To deny the conclusion, you need to maintain that the MGB is logically impossible; that it contains a logical contradiction, and hence does not exist in any possible world. You need to maintain that premise 1 (section IV) is false. "Weak atheism" is out, otherwise you fall prey to premise 1 and the conclusion of the argument.

See here for an argument for the possibility of the MGB.

Alvin Plantinga's Modal Ontological Argument: Express Version

I. A Supercomputer

Imagine a powerful super computer that simulates every alternate reality that is logically possible.

 

Some simulations contain the same stuff the real world contains, such as elephants and rocks. Some simulations contain characters that are merely fictional in our world, like Superman and Batman.

And some things, such as illogical objects, are not to be found in any of the simulations. No simulation will contain triangles with four sides, or married bachelors, for example.

And yet other things will be true in all the simulations. 2+2=4, for example, will be true in every simulation and cannot be false.

II. Greatness

Use the dictionary definition of "great": unusually or comparatively large in size or dimensions; unusual or considerable in degree, power, intensity, etc

III. Maximally Great Being

What is classically referred to as "God" in Western religion is a maximally great being: one with all his attributes maxed out. A being that is the creator and sustainer of everything other than himself, and of which there is none greater.

IV. The MGB Simulated

As long as there is no logical incoherence in the concept of a maximally great being, then it "exists" in one of the simulations.

V. All Simulations

But a maximally great being would have to exist in all the simulations. If it existed in only some of the simulations, then it would not by definition be maximally great. It is greater (see above for the definition of great) to exist in three simulations than only two, to exist in four simulations than only three, etc. The greatest being would exist in all simulations. Another way to think about it is that if the MGB is the creator of everything, and all simulations have to include something in them, then the MGB is in all the simulations as well.

VI. In the Real World

If the MGB exists in all simulations, then it exists in the real world as well since one of the simulations is identical to the real world.