Part of the problem involves explaining how we can know of other consciousnesses than our own. Say I were to remove another person’s brain. They would then be dead; does this mean that they’d suddenly lack a mind? What if they still retained their unconscious sub-mind and simply lost the ability to be conscious at all?
The only person who could absolutely verify that their own consciousness exists is him- or herself. But, in the above example, we could no longer ask our brain-less person if they were conscious and receive a response.
If we can’t perform this falsification meaningfully on another person, then how about on ourselves? Suppose now that, instead, I were to remove my own brain. No one else could be certain that my consciousness exists; could I still be, without a brain? Would “I” exist in any way that would allow me to check the status of my own consciousness? Only if I were conscious. There seems to be a circularity embedded in this approach that might render the whole matter unresolvable.