|OK, let me try again.|
First, Ted, old buddy (was it about 8 years ago we met and haunted Borders in Manhatten?), I didn't mean to imply that you believed in parallel universes. I was just making a quick and messy adaptation of "close, but no cigar." Sorry for any confusion I may have caused. And yes, if we can't have fun (and maybe learn something, too), what good is all this? :-)
Now, about your proposition....
I have trouble trying to phrase denials of propositions that are not stated in S-P form. Also, I think that when we are dealing with things that don't exist, we can get in trouble. (E.g., The King of France is bald vs. The King of France is not bald. If one is false, the other must be true, right? Wrong. But that's another story -- or another post, at least.)
But let's give it a go, and I'll try to engage in generous (i.e., generously minimal) paraphrasing...
You are claiming that Nothing (no thing) prevents Existence or the universe from existing. You wisely dropped your original claim that Existence exists because nothing prevents it from existing.
Your modified claim this states that no thing is a thing that prevents the universe from existing. True enough. And if we try to negate it, we have: some thing is a thing that prevents the universe from existing. This is false and impossible. Even if there were some one thing that could (somehow) annihilate (probably by assimilating into itself?) every other thing that existed, it would still have to exist itself. In other words, it is impossible for the sum total of Existence (whether that sum total is many things or just one thing) to be prevented from existing. So, there can be no cause of its being prevented from existing. I certainly don't object to that.
The seductive nature of your claim lies in the fact that it seems similar to more mundane claims that are relevant to make. For instance, I can say that Nothing prevents me from breathing, which means that no thing is a thing that prevents me from breathing. However, there are things that could prevent me from breathing (e.g., asphyxiation, apnea, etc.), so there is relevance in saying that no thing does in fact prevent me from doing so. X could prevent me from breathing, but in fact it doesn't. But in the case of the universe, there are no things that could prevent it from existing, so there is no relevance in saying that no thing does in fact prevent it from doing so. For all X, X in fact doesn't prevent Existence from existing, because it can't.
Also, I am breathing not because nothing is preventing me from breathing, but because my central nervous system directs me to. However, in the case of the universe, it exists not because nothing is preventing it from existing, nor for any other reason. It simply exists.