He doesn't know for sure, it is just the simplest and most likely theory that fits the facts as we know them - consciousness arises from certain complex arrange

He doesn't know for sure, it is just the simplest and most likely theory that fits the facts as we know them - consciousness arises from certain complex arrangements of living cells, and is not known to exist outside of those conditions. You can speculate to your heart's content, but until you have some evidence to suggest the current theory of conciousness is mistaken and that yours fits observable reality better, then your speculation will remain just that.