[I'm probably going to be the latest in a long line of people saying something like this, but I hope my wording, at least, makes this worth existing.]

"I think, therefore I am" is, in fact, deductive reasoning. The definition of "I am", as thought in the first person, as far as we can comprehend it, means "I think".

"I think, therefore I think" Or, more simply, "I think". The statement itself, as we are thinking it, cannot possibly be false - no matter the Demons we posit, we cannot be in simultaneous states of comprehending and not thinking.

"I am", by our very definitions, must be true for everyone who is reading this, as you are reading it. Because you are reading it.

I'm sorry, Eliezer, but I think you are mistaken if you think you can disprove "I am", thought in the first person.