The Ontological Argument - valid or debunked?

[GrandizerII]

wiploc's argument shows that it can work both ways, that's the point. As you have yet to provide an argument that establishes the logical possibility of a maximally great being, then this argument is pretty much vacant at this point.

No. It does not work both ways because the meaning of P4' is very different from P4 because you cannot rely on modal logic of "necessary" as the original argument does.

So? Still valid argument, with conclusion following logically from the premises.

Even William Lane Craig acknowledges this:

Now you're absolutely correct, Randy, in noting that if we alter the first premiss to read
1′. It is possible that a maximally great being does not exist,
then the conclusion follows that
6′. Therefore, a maximally great being does not exist.
There's no fallacy here. The whole question is, which do you think is more plausibly true: (1) or (1′)?

Read more: http://www.reasonablefaith.org/necessary-existence-and-the-ontological-argument#ixzz4CoByxm58