[dustin_archibald]

Originally Posted by <<>>

But then what doesn't exist is not in everythng so everything is not everything if whatevr doesn't exists is a thing or something, and as for example a horse with wings (can't remember the name given in the greek myth) is a thing and dosn't exist, so it must be in everything.

The winged horse is Pegasus. The idea or thought of Pegasus exists therefore it (the idea or thought) is covered under "everything".

If you wanted to you could say that "everything" is all that exists or does not exist but that would ultimately lead to all things in existence being Everything. If you want to get into sets (please excuse my notation, it's been a while since logic courses):

Definitions and assumptions:

1. A={Non-existence}={}
   1. We say that A is the empty set since it has no items (technically it has all of the items that do not exist).
2. B={Existence}
   1. This set includes all things that have existed, do exist, and will exist (as per my original post)
3. C={Everything}

Calculations:

1. C=A U B
2. C= ø U B
3. C=B
4. {Everything}={Existence}

Now I haven't fully documented the proofs (Ex: axiomatic, BY 3, etc.) but the logic is still sound. I think.

Adding to this discussion we can give definitions for Existence and Non-existence as discussed here which we can all agree are axiomatic.