I have a confession to make. I have never understood the idea of "necessary existence". I cannot fathom how it changes anything. I'm not even sure if I have a handle on what it is supposed to mean.
The idea is that a "Necessary Being" is one that has
to exist, because its non-existence would entail a logical contradiction, like "square circle" or "non-existent existence." The real purpose of this concept as employed in ontological arguments (better term: antilogical arguments
) is to serve as the conceptual handkerchief in a slight-of-mind trick. First we can notice things such as the assumption of the singular (i.e., not "Necessary Beings"), and the use of the term Being, which smuggles in connotations of personhood, as silently steering away from other possibilities like Necessary Force or Necessary Principle, or the plurals thereof. The goal is to sneak the following equation into the mark's mind:[(God) + (Has to exist!)] = Yahweh
On the left side of the equation, the trick is to smuggle "existence" into the definition
of (generic) "God." Once the mark swallows that package-deal, they will be compelled to accept the claim that "God does not exist" is a logical contradiction. The beauty of this trick is that it spares the theist from ever having to actually demonstrate
that a god (generic or otherwise) exists. Then, moving across the equal sign to the right, the "prestige" of the trick is completed: a bait-and-switch where the generic placeholder is changed into Yahweh from the Bible. Watch how Anselm does it:
1) We shall define "God" to be a "being than which no greater can be conceived"
(I'll abbreviate this to "GCB")
2) We can have an understanding of such a GCB in our minds, so it exists in our understanding.
3) The concept must exist either only in our understanding, or in our understanding and reality.
4) If it existed only in our understanding, it would be less Great than it would be if it existed in our understanding and in reality.
5) A GCB that existed only in our understanding would not be a GCB (since an existing GCB would be Greater).
6) Therefore, a GCB must exist in our understanding and
in reality, or there would be a logical contradiction.
The whole trick depends on the definition.
If we were to use a more honest definition, such as "We shall define 'God' as 'A triune Being Whose members are Yahweh, Jesus, and the Holy Spirit as portrayed in the Bible,'" the argument could never get off the ground. There is no reason a priori to equate the Biblical deity with a "Greatest Conceivable Being." It would be very easy for someone to say, "Hang on! I can conceive of a Being greater than that
!" That equation is never actually justified
by the theist. Instead, the theist counts on the mark's own cultural biases in favor of One Big Christian Mono-God to perform the transformation. It would never fly in a culture where, say, a "Pleroma" ("fullness") of plural divinity, a Pantheon, was assumed to be Greater than any single deity alone, or where a male-only concept of divinity was felt to be inferior to one that incorporated the Divine Feminine in some way to form a balance.
Peterofthecorn's trick is basically the same thing, only clumsier, as he forgot to use a handkerchief. His argument tries to attach the modifier "existing" onto "God" so the two words form a single definitional unit, a package-deal. Lacking Anselm's devious subtlety, POTC got caught by the audience because the definitional trick was too obvious, hanging out in plain view as the modifier "existing" instead of being slipped into the definition of "God" before executing his syllogism.