I’m putting this in the Philosophy section, but as I’ll show, it crosses over to science and even pop culture. One of the difficulties of discussing it is semantics. The IEP helps with that.
It appears that even a complete specification of a creature in physical terms leaves unanswered the question of whether or not the creature is conscious. And it seems that we can easily conceive of creatures just like us physically and functionally that nonetheless lack consciousness. This indicates that a physical explanation of consciousness is fundamentally incomplete: it leaves out what it is like to be the subject, for the subject. There seems to be an unbridgeable explanatory gap between the physical world and consciousness. All these factors make the hard problem hard.
To argue for consciousness existing in simpler life forms or even at a cellular or near cellular level doesn’t solve the problem for me. Demonstrations of worms or roots appearing to decide to turn one direction or another don’t illuminate the mechanisms in those organisms that create them feeling that they made a decision. Even if it is the same chemical and physical forces that lead me to create something I call “artistic”, the nature of that chemistry and force is still left unexplained. The question remains;
What makes the hard problem hard and almost unique is that it goes beyond problems about the performance of functions. To see this, note that even when we have explained the performance of all the cognitive and behavioral functions in the vicinity of experience—perceptual discrimination, categorization, internal access, verbal report—there may still remain a further unanswered question: Why is the performance of these functions accompanied by experience?
Rather than attempt to sort out Scientific Reduction, I’ll refer to section 4.4.2 there. And, I acknowledge that reductionism can focus too much on the details and miss the complexity of the whole that arises from the details. However that doesn’t relieve those who claim there is only the “easy problem” of consciousness from doing some heavy lifting to get from lower-level phenomena to the answer.
Since they retain their grip on philosophers, scientists, and lay-people alike, we can conclude that no functional characterization is available. But then the first premise of a reductive explanation cannot be properly formulated, and reductive explanation fails.
Perhaps, the “answer” or the “goal” is where clarity is needed, not unlike the question that was not properly formulated in The Hitchhiker’s Guide to the Galaxy. We have not defined the mechanisms that create gravity, but we know it is a force and we can use it to land things on distant planets. If we have a formula that explains consciousness or can point out the parts that create it, does that bring us closer to caring about the future of life here on Earth?