By thinking about what a computer is actually doing & realizing that attributing thought to an arthmetic gadget leads to all sorts of nonsensical consequences like an arrangement of dominoes & their cascade being a thought. The metaphysics of thinking computers is incoherent & if you study computability theory you'll reach the same conclusion.▲
I've already explained it in several places. The burden of proof is on those drawing the equivalence to provide actual evidence for why they believe carbon & silicon are interchangeable & why substrate independence is a valid assumption. I have studied this problem for much longer than many people commenting on this issue & I am telling you that your position is metaphysically incoherent.