It seems to me a useful principle of rational thought is that we should use as few terms as necessary. If two terms are so similar as to be identical, then they’re equivalent and one is redundant.
Libertarian argues that if it’s possible for a thing to be, it exists. He’s not suggesting that the possibility exists, but that the thing that is possible exists. He then makes a further distinction between actual things and merely possible things.
If something is possible, it exists.
If something is impossible, it doesn’t exist.
Now consider that Libertarian exists, and is actual. It seems rather odd to suggest that he must necessarily be alive, so we can determine that it’s possible that he could be dead, even if he isn’t (dead Lib isn’t actual). Therefore, living-Lib and dead-Lib both exist. We can make no distinctions between the two from logic alone. We can continue this with everything that it’s possible for Lib to be, and conclude that every possible him exists.
It seems to me that this makes the concepts of “existence” and “possibility” equivalent in every way. There’s no way something can exist but be impossible, be possible but not exist, be impossible but exist, or not exist and be possible.
Meanwhile, the concept of “actual” existence (as opposed to virtual) has all the properties of the general meaning of “existence”.
I conclude from this that Libertarian’s suggested definitions of possibility and existence are pointless. Accepting them changes nothing about what we can conclude or what we know; instead, it merely results in the renaming of concepts.
Therefore, I hold that we should reject the idea that a thing that is possible exists. We can speak of the possibility existing, but not of the thing. The standard meaning of “existence” should be used instead of the concept of actuality, which is equilvalent in every meaningful way.