The basis for believing this is the inference that because the physical world insofar as we have knowledge of it obeys physicalist principles, so must the human

The basis for believing this is the inference that because the physical world insofar as we have knowledge of it obeys physicalist principles, so must the human mind. But we can't really claim to know based on our investigation of the mind itself. If we entertain theories of consciousness like dualism, monism or emergentism, it seems unlikely that we have the categories of understanding and analysis to decisively confirm or deny them.