Let's explain in more detailed way the following quote:
"Tautology of existence" means that existence is logically always true, whether it is discovered or not. This kind of existence is known as platonic.
This notion is notated in my posts by the outer "{" and "}".
What is between the outer "{" and "}" is not "Tautology of existence" (it is non-platonic), because one of the options is {} (there is nothing between the outer "{" and "}").
"Tautology of existence" holds whether there is nothing or there is something between the outer "{" and "}", or in other words, what is between the outer "{" and "}" is logically not a "Tautology of existence" (it is non-platonic) and therefore it is logically inaccessible to the platonic.
By understanding the logical difference between platonic and non-platonic levels of existence, one easily understands that actual infinity is at the platonic level (notated by the outer "{" and "}"), which is logically inaccessible by any amount of members exactly because their existence is logically restricted only to the non-platonic level (members may exist, or not).
If one understand this post, he\she can easily understand
http://www.internationalskeptics.com/forums/showpost.php?p=10034959&postcount=3854.