The Modal Logic version (Alvin Plantinga and William Lane Craig) of the Ontological Argument has received much attention and seems to have caused grief. But all attempts so far have not quite succeeded in demolishing the argument. A different approach, as described below, may just be the successful attempt. But it may take a little bit of thought to understand. Try it.
1. The construct known as a "Possible World" means either (a) the Actual World that we inhabit, or (b) a Hypothetical World.
2. The construct known as a "Possible Worlds Set" means a set (of Possible Worlds) whose members all satisfy a particular set of criteria.
2a. The construct known as the "All Possible Worlds Set" means the set that contains every Possible World with only one qualification - no logical contradiction is permitted in any Possible World.
3. The construct known as "Necessary" means that that which is designated as Necessary in the context of a particular Possible Worlds Set, is true and identical for each and every member of that Possible Worlds Set.
3a. Thus if a particular Possible World is contained in a particular Possible Worlds Set, in that Possible World, that which is designated as Necessary for that Possible Worlds Set, is true. Otherwise that Possible World could not possibly have been included in that Possible Worlds Set.
4. If a Possible World fails to qualify for inclusion in a particular Possible Worlds Set, this Possible World will qualify for inclusion in another (different) Possible Worlds Set which has its own (different) qualification criteria. If we then have more than Possible Worlds Set, each such set will be a sub-set of the All Possible Worlds Set.
5. If a Modal Logic argument uses the construct known as Necessary, then the Possible Worlds Set referenced by that argument can only be the one whose member qualification criteria include that this particular Necessary is true.
6. For the Modal Logic Ontological Argument, the chosen Necessary is the existence of the Maximally Great Being. It follows that the Possible Worlds Set that is referenced by this particular Modal Logic argument is the one whose members each contain the Maximally Great Being. By being members of this Possible Worlds Set, each member has been previously assessed as containing the Maximally Great Being. The Actual World that we inhabit has not been assessed as containing the Maximally Great Being and so is not a mermber of this Possible Worlds Set. Hence this Modal Logic Ontological Argument cannot conclude anything about the Actual World that we inhabit other than that it has not been assessed as containing the Maximally Great Being. Thus the Modal Logic Ontological Argument fails to show that the Maximally Greart Being exists in the Actual World that we inhabit.