I have a number of issues with the Ontological argument.
1. It is possible that a maximally great being exists.
As defined (morally perfect, all knowing, all powerful) I don't believe that an MGB can exist. I am an incompatibilist when it comes to free will vs. omniscience.
2. If it is possible that a maximally great being exists, then a maximally great exists in some possible world.
Tautological; this is the definition of "possible."
3. If a maximally great exists in some possible world, then it exists in every possible world.
This does not follow from anything. It is usually stated that if it didn't exist in some possible world then it wouldn't be "maximally great" but this attribute of the MGB is not included (and does not step from) its definition. Furthermore, the definition of a being describes its existence in a possible world whereas saying it exists in all possible worlds is a meta description of it. Whether it exists or doesn't exist in one possible world vs. another has no impact on the nature of its existence in the worlds it does exist.
In short, this is saying that the MGB is necessary, that its nonexistence would constitute a logical contradiction, but this is not demonstrated.
4. If a maximally great being exists in every possible world, then it exists in the actual world.
This is taken as a given.
5. If a maximally great exists in the actual world, then a maximally great being exists.
Tautological.
6. Therefore, a maximally great being exists.
We can summarize this argument more succinctly:
1. It is possible that a maximally great being exists. (◇MGB)
2. If a maximally great being is possible, then it is necessary. (◇MGB → □MGB)
3. If a maximally great being is necessary, then it is actual. (□MGB → MGB)
4. A maximally great being is actual. (MGB)
This structure is valid, but are the premises (#1 & #2) true?
Franklin attempts to define God into existence by saying that it is a necessary being because if it wasn't it wouldn't be god. This is circular and tautological. You can't include "is true" in the definition of a statement and then consider the definition true.