You can give argument though. It is concievable it is possible to prove things like: a turing machine (which is an abstract mathematical model, which we absolutely can prove negatives. See for example rice's theorem) can never achieve "human intellegence" (if you come up with a concrete definition of human intelligence). From there you can make the statement: Any physically realized device that is faithfully modelled in terms of computational power by a turing machine, cannot have "human intelligence".

Sure you can't prove that silicon devices behave like turing machines, or even that they really exist, but for the sake of this discussion, what does that matter?