Alright, here's an idea: consciousness is spectrum that occurs when a system develops an automatic self-correcting mechanism for interacting with the external physical universe. In some sense all animals (including humans) wandering on this planet are conscious, because we all learn to build our actions around interactions with the external physical universe, e.g., we learn how to walk/swim/fly under the force of gravity without falling/crashing, we learn that the square peg fits in the square hole and not in the round hole, etc. The feedback from these interactions allows us to automatically adjust our future actions without external help. In this sense we learn what works, aka. what is "true" (at least under the laws of this universe). Some animals happen to have "higher" consciousness in that they interact with the universe in more sophisticated ways, learning "deeper" truths, but all animals possess some degree of consciousness under this definition (my cat is certainly consciousness, she has learned how to manipulate the external world, especially me, perfectly at this point). Consciousness is a matter of degrees, not a binary property that one can satisfy.

This definition also has the nice property of showing why current LLMs don't fit on the spectrum. They don't have any concept of learning what is true and automatically self-correcting. They will happily tell us things that are obviously not true, e.g., the square peg fits in the round hole, and then insist that they are right, when a basic physics experiment will disprove their assertions. Interestingly though, things like linear feedback control systems like we might find in an elevator do possess some degree of consciousness: they interact with the physical world, identify the true position of the elevator, move it where they want, and self-correct when necessary. They might be primitive, but I for one believe that they are certainly "conscious" at some level, and definitely more than LLMs. :)

Almost certainly this definition is incomplete and flawed in many aspects, but I think it's at least self-consistent.