How can you know that any animal, other human beings, or anything that seems conscious, isn't just faking it? Does it enjoy an internal subjective experience, complete with sensations and emotions like hunger, joy, or sadness? After all, the only consciousness you can know with certainty is your own. Everything else is inference. The nature of consciousness makes it by necessity a wholly private affair.
These questions are more than philosophical. As intelligent digital assistants, self-driving cars and other robots start to proliferate, are these AIs actually conscious or just seem like it? Or what about patients in comas — how can doctors know with any certainty what kind of consciousness is or is not present, and prescribe treatment accordingly?