> Why must a concept be empirical and objective?

Because otherwise it's your word against mine and, since we both probably have different definitions of consciousness, it's hard to have a meaningful debate about whether bats, cats, or AI have consciousness.

I'm reminded of a conversation last year where I was accused of "moving the goalposts" in a discussion on AI because I kept pointing out differences between artificial and human intelligence. Such an accusation is harder to make when we have a clearly defined and measurable understanding of what things like consciousness and intelligence are.