That path leads to a world of hurt: what does "actually exist" mean?

Isn't it enough that we can perceive consciousness or its absence in ourselves and others? Isn't it enough to define it (my words, not very carefully thought out) as something that at least entails the capability to think about a situation, real or hypothetical, including your own state and thoughts and communications, understanding some of the consequences of action in such a state, choosing an action, accepting responsibility, etc., up to philosophy, meta-cognition and beyond?

The fact that it's hard to define, doesn't mean it doesn't exist.