The ontological argument that was explained over the last several weeks (click to see it here) brings up several questions and versions. We will be going over some of them for the next few weeks.
Here is an explanation of the Modal version of the argument:
Modal Version
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.
Question:
Just because GCB must be thought of as existing, does that mean that GCB really exists?
Reply: 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.
Kreeft, P., & Tacelli, R. K. (1994). Handbook of Christian apologetics: hundreds of answers to crucial questions (p. 71). Downers Grove, IL: InterVarsity Press.