20 Arguments for God's Existence: Argument #13 - The Ontological Argument (Pt. 2)

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Last week, we took a look at St. Anselm of Canterbury's original version of the Ontological Argument for God's existence, as presented by philosopher Peter Kreeft.  This week, we consider Kreeft's explanation of Modal Ontological Argument.  

Kreeft Writes:

Charles Hartshorne and Norman Malcolm developed this version of the ontological argument. Both find it implicitly contained in the third chapter of Anselm's Proslogion.

1. The expression "that being than which a greater cannot be thought" (GCB, for short) expresses a consistent concept.
2. GCB cannot be thought of as: a. necessarily nonexistent; or as b. contingently existing but only as c. necessarily existing.
3. So GCB can only be thought of as the kind of being that cannot not exist, that must exist.
4. But what must be so is so.
5. Therefore, GCB (i.e., God) exists.1

Kreeft then highlights and responds to one challenge to this form of the argument.

Challenge

Just because GCB must be thought of as existing, does that mean that GCB really exists?2

Response

If you must think of something as existing, you cannot think of it as not existing. But then you cannot deny that GCB exists; for then you are thinking what you say cannot be thought—namely, that GCB does not exist.3

Kreeft concludes by offering a summary of the Modal Ontological Argument offered by philosopher Alvin Plantinga featuring the idea of possible worlds.

He writes:

This variation on the modal version has been worked out in great detail by Alvin Plantinga. We have done our best to simplify it.

Definitions:

Maximal excellence: To have omnipotence, omniscience and moral perfection in some world.

Maximal greatness: To have maximal excellence in every possible world.

1. There is a possible world (W) in which there is a being (X) with maximal greatness.
2. But X is maximally great only if X has maximal excellence in every possible world.
3. Therefore X is maximally great only if X has omnipotence, omniscience and moral perfection in every possible world.
4. In W, the proposition "There is no omnipotent, omniscient, morally perfect being" would be impossible—that is, necessarily false.
5. But what is impossible does not vary from world to world.
6. Therefore, the proposition, "There is no omnipotent, omniscient, morally perfect being" is necessarily false in this actual world, too.
7. Therefore, there actually exists in this world, and must exist in every possible world, an omnipotent, omniscient, morally perfect being.4

For those who want to learn more about this version of the argument, I recommend this short animated video by philosopher William Lane Craig.  Further, philosopher Thomas Metcalf offers a great introduction to the argument here.

Finally, Miquel of Smart Faith was kind enough to share this excellent piece he wrote explaining how the ontological argument can be used in faith conversations.  

Courage and Godspeed,

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