The authors of the paper seem to define what they mean by consciousness quite precisely. They mean phenomenal consciousness: >The central goal of any C-test is

The authors of the paper seem to define what they mean by consciousness quite precisely. They mean phenomenal consciousness: >The central goal of any C-test is to determine whether a target system has subjective and qualitative experience – often called ‘phenomenal consciousness’. Phenomenal consciousness is, as far as I can tell, binary. You either have subjective experience or you don't. Even if you are subjectively aware of almost nothing, you still have subjective experience. For example, when you wake up in the morning your awareness might be quite limited for the first few seconds - let's say you have your eyes closed and the only thing you are aware of is the warmness of the blanket. But still, you are aware. You have subjective experience. Whereas in deep sleep you do not. Phenomenal consciousness is thus pretty well-defined. It's just that we have zero understanding of how physical systems could possibly give rise to it, and it might be in principle impossible to ever figure that out. It is possible that physical systems do not in fact give rise to consciousness, although obviously the presence vs absence of consciousness in humans is at least to some extent correlated with certain measurable physical states. I doubt that any actual test for consciousness is in principle possible, but the authors of this paper do at least clearly define what they mean when they refer to consciousness. They mean the presence of subjective experience, not intelligence or language or logical thought or having a model of oneself or any other things.