- Necessarily: If a perfect being exists, then it is necessary that a perfect being exists. (Premise)
- It’s possible that a perfect being exists. (Premise)
- It’s possible that it is necessary that a perfect being exists. (By 1 and 2)
- If it
is possible that
*P*is necessary, then*P**is*necessary. (Premise “S5”) - So, it is necessary that a perfect being exists. (By 3 and 4)
- So, a perfect being exists.

Why 1? Because being *essentially*
perfect and being *necessarily*
existent are perfections.

Why 2? Here’s the rub.

Why 4? *P* is necsessary if and
only if *P* is true in every possible
world. What is necessary does not vary between possible worlds. So, if *P* is necessary in one possible world,
it’s necessary in all of them, and hence it is necessary in the actual world.

1. If a perfect being exists, then it is necessary that a perfect being exists. (Premise)

2. It’s possible that no perfect being exists. (Premise)

3. If it’s possible that no perfect being exists, then no perfect being exists. (By 1)

4. So, no perfect being exists. (By 2 and 3)