Descartes was definitely a great person...

I think, therefore I am.

But then it became clear that the statement is not accurate, so it had to be reviewed:

I think that I think, therefore I think that I am.

And now you're ready for the final strike:

Descartes is having a drink in a bar... "Have another, sir?" says the bartender; "I think not" says Descartes, and disappears!

Ans since we're here, let me share some boolean-prologish humour with you:

A logician tells a collegue his wife just had a baby.

- Is it a boy or a girl?
- Yes.

A mathematician is in an elevator, which stops at a floor and opens. The person waiting asks, "Is this elevator going up or down?" And the mathematician answers:

1. Yes. (Same as the boy or girl joke)
2. No. (Since the elevator has stopped)