Said "I can prove that I exist; I think, therefore I am!"
I'd like to pose a question, though, that puts him on the spot:
A table doesn't think, so does that mean that it is not?
That verse was written by your friendly, neighborhood Halmanator back in the days of his youth, when he fancied himself a poet.
My tongue was, of course, planted firmly in my cheek when I wrote that verse. As any logician will tell you, just because a premise is true, it does not automatically follow that its opposite is also true. To wit: although thinking or self-awareness can be considered proof of an entity's existence, it does not follow that any entity which is not self-aware and unable to think does not exist.
We might extend the argument to say that an entity can also prove its existence by imposing itself upon the thoughts of one or more other sentient entities. If you or I think about the table, we acknowledge its existence even though the table itself has no self-awareness or thought.
But if we accept that, we may blunder into the following challenge: Hundreds of thousands of young children believe in Santa Claus. They think about him so, given the previous argument, that is proof of Santa's existence. But of course, Santa Claus doesn't exist ... or does he?
Perhaps the argument can be made that anything that occupies the thoughts of another does exist in some sense, especially if it occupies the thoughts of multiple others. The tooth fairy, the bogeyman, Bugs Bunny, Darth Vader, Tom Sawyer, el chupacabra, Superman, Little Red Riding Hood and, yes, even God. It may be argued that all of them exist in some sense, if only because we, the human race, have willed them to.
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