I exist.

This I know with absolute certainty, for I think, therefore I am. But since you, gentle reader, have only my word that I think, you cannot be certain that I am. And since I cannot meaningfully tell you about who I am without first demonstrating that I am, I shall dedicate this space to establishing the fact of my existence rather than elucidating the nature of it. Here goes.

That which does not exist, does not exist. Therefore, there is no such thing as that which does not exist. But if there is no such thing as that which does not exist, then I must exist--for I cannot be an example of that which there is no such thing as. So I exist, QED.

But on the other hand, absolute and irrefutable proof of my nonexistence must exist also--for absolute and irrefutable proof of my nonexistence also cannot be an example of that which there is no such thing as. Therefore I must not exist after all.

So never mind then.