Donald: I think I am a duck. Therefore I must be a duck.
Douglas: You mean, you walk like a duck, quack like a duck, so you must be a duck?
Donald: Is there a difference?
Douglas: There is. You look like a duck. You quack like a duck. Therefore, it is possible you belong to the Anatidae family. But it doesn’t mean you can think.
Donald’s identity problem can be explained by…
(a) Cartesian logic.
(b) Cartesian linguistics.
(c) Cartesian diving.
(d) Cartesian coordinates.