The Ontological Argument

This argument is used very little amongst Christians who defend the faith, and I see why, as it seems like very abstract reasoning. But despite this, I think it is a very convincing argument once you think about it. This argument makes a case that a God must exist based on there mere concept of what it means to be "God". The argument has a rich history and many versions, but I like the Alvin Plantaga's version of it, which I will use with my own little twist. The argument is as follows; 1. God, by definition, is a maximally great being that exists necessarily. (By "great", it is meant that God has certain attributes as omnipotence, omniscience, ominpresence, and omnibenevolence). 2. It is possible for a maximally great being to exist in some possible world. 3. If it is possible for a maximally great being to exist in some world, it is possible for a maximally great being to exist in this world. 4. If it is possible for a maximally great being to exist in this world, then a maximally great being must exist in this world. 5. Therefore, God exists. Explanation of #1: The word "great" here is used to define a "quality" of existence. Those attributes are "great making" qualities. So to have maximally great knowledge is to know EVERYTHING (omniscience). To have a maximally great presence is to be EVERYWHERE at one time (omnipresence). To have maximally great power is to be able to do ANYTHING that is logically possible (omnipotence). And to be a maximally great benevolent person is to be the ultimate source for what it means to have a good moral character (omnibenovelent). In the first sentence of #1, God exists necessarily, meaning that if God exists, it is impossible for him to cease existing. Explanation of #2: Simply means that we can imagine a world at which a maximally great being could exist. If such a being "could" exist, then its a least possible for it to exist. Explanation of #3: If a maximally great being could exist in a world that we don't know about, then that same maximally great being would have to exist in THIS world. Because remember, to be a maximally great being is to be omnipresent, so if a maximally great being is present in another world, this same being would also have to be present in this world. If a maximally great being does not exist in this world, then this being was never maximally great, because if it was, there would be no limitations to where it could be present. So a maximally great being would have to exist in this world if it was possible that it could exist in another world. Explanation of #4: We can all admit that it is at least possible for a maximally great being to exist in another possible world. So if it exists in another possible world, it would have to exist in this world. If it is possible for a maximally great being to exist in this world, then a maximally great being DOES exist in this world. Remember, the existence of a maximally great being would be a NECESSARY truth, meaning that it would be impossible for this being to NOT exist in ANY world. But it cant be impossible, because we already know that it IS possible for a maximally great being to exist in any possible world. As long as this is even POSSIBLE, it must be true, because all necessary truths MUST in fact be TRUE. Now in order for Con to dismantle this argument, Con must explain why the existence of a Supreme Being is impossible...why the concept of such a being is logically absurd, and I don't think anyone can do this.