The Stanford Encyclopedia of Philosophy article called "Zombies" https://plato.stanford.edu/entries/zombies/ makes no mention of an assumption that seems to be hidden in the famous philosophical zombie question. Using the search text function of my browser I looked at every instance of the string "assum" so as to examine every time the word "assume" or "assumption" or "assuming" or "assumed" in the entire long article.
Likewise, searching the article for "circ" to check for any mention of possible circularity or arguing in a circle turned up nothing relevant. Ditto for "beg".
The assumption I am referring to is that normal human beings are not philosophical zombies, in other words, the assumption is that normal humans have qualia and conciousness.
Here's the beginning of the SEP article: " Zombies in philosophy are imaginary creatures designed to illuminate problems about consciousness and its relation to the physical world. Unlike the ones in films or witchcraft, they are exactly like us in all physical respects but without conscious experiences: by definition there is ‘nothing it is like’ to be a zombie. Yet zombies behave just like us, and some even spend a lot of time discussing consciousness.
Few people, if any, think zombies actually exist. But many hold they are at least conceivable, and some that they are possible. It seems that if zombies really are possible, then physicalism is false and some kind of dualism is true."
There seems to be an implicit assumption that ordinary humans have consciousness and qualia. It's just taken to be a fact that can be used without acknowledgement.
I hope this isn't a digression, but it seems relevant to me that it says, "Few people, if any, think zombies actually exist." "if any". What? Dan Dennett said we are all zombies. There are clearly some people who think zombies exist, so this is flat out wrong. And that's not to mention the superstitious people all over the world who believe in walking corpses.
Dan Dennett famously said that we are all philosophical zombies. Wikipedia says in its article called "Philosophical zombies", "Some physicalists like Daniel Dennett argue that philosophical zombies are logically incoherent and thus impossible, or that all humans are philosophical zombies;" https://en.wikipedia.org/wiki/Philosophical_zombie
Turning now to the way the Wikipedia article handles the zombie idea, the idea is introduced with the following paragraph: "A philosophical zombie argument is a philosophical thought experiment which conceptualizes a hypothetical being that is physically identical to and indistinguishable from a normal person, but does not have conscious experience.  For example, if a philosophical zombie were poked with a sharp object, it would not inwardly feel any pain, yet it would outwardly behave exactly as if it did feel pain, including verbally expressing pain. A philosophical zombie would not possess consciousness acting only on instinctual programing, and actions of which respond to the stimuli of the world around them." No mention of the assumption that ordinary humans have consciousness and qualia.
Instead of stating in the intro of the Wikipedia article when defining the zombie idea the assumption that normal humans have consciousness and qualia, the assumption is mentioned in passing and in parentheses in a sentence buried (I found it with an automated seach for the string "assum") deep in the body of the article: "When a distinction is made in one's mind between a hypothetical zombie and oneself (assumed not to be a zombie), the hypothetical zombie, being a subset of the concept of oneself, must entail a deficit in observables (cognitive systems), a "seductive error" contradicting the original definition of a zombie. " The extremely complex verbiage (I, for one, cannot make head or tail of it) makes it very hard to even figure who it is allegedly assumed by that oneself is not a zombie. It is far from being a clear statement that the zombie idea contains the assumption that ordinary humans have consciousness and qualia. So, although better than the SEP article, which doesn't even mention the assumption, the Wikipedia article is only a little better, and is guilty of not mentioning the assumption when defining the idea of a zombie at the outset.
What about Chalmers himself? His website introduces the zombie idea like this https://consc.net/zombies-on-the-web/: "Zombies are hypothetical creatures of the sort that philosophers have been known to cherish. A zombie is physically identical to a normal human being, but completely lacks conscious experience. Zombies look and behave like the conscious beings that we know and love, but "all is dark inside." There is nothing it is like to be a zombie.
Varieties of zombies
There are actually three different kinds of zombies. All of them are like humans in some ways, and all of them are lacking something crucial (something different in each case)."
No acknowledgement by Chalmers that it is assumed that ordinary humans have consciousness and qualia, nor that anyone doubts this.
Later on in Chalmer's article it says, "It can be used as a way of illustrating the "hard problem" of consciousness: why do physical processes give rise to conscious experience? This question might equally be phrased as "why aren’t we zombies?". If any account of physical processes would apply equally well to a zombie world , it is hard to see how such an account can explain the existence of consciousness in our world." "Why aren't we zombies?" There's the assumption that we aren't, but it's not acknowledged.
And then, "It can be used to raise questions about the function of consciousness: why did evolution bother to produce us if zombies would have survived and reproduced just as well? (As e.g. Flanagan and Polger have argued.)"
He seems to me to be assuming what he has set out to prove.
Interestingly, Chalmers does subtly acknowledge (IMHO, by placing the words "do more work" in quotes) that the existence of God is moot in this paragraph: "And it can even be used to argue against materialism. If there is a possible world which is just like this one except that it contains zombies, then that seems to imply that the existence of consciousness is a further, nonphysical fact about our world. To put it metaphorically, even after determining the physical facts about our world, God had to "do more work" to ensure that we weren’t zombies." But he doesn't let the reader know that the there are more than one school's of thought that regard "consciousness" and "qualia" as moot (consciousness illusionism (Keith Frankish) https://www.youtube.com/watch?v=Y2n-s6C1iYQ&list=PLhgvALi0LQGXIA7cKNmGNTiQ7dpS-7dLw and eliminative materialism https://plato.stanford.edu/Archives/Win2004/entries/materialism-eliminative/ to mention two that I know of, and one could arguably add heterophenomenology, behaviorism, and logical positivism).
And searching for "assum", "circ", and "beg" yielded nothing in the Chalmers article.
Allow me to make an analogous "free-will zombie" argument/thought experiment. "A free-will zombie is just like a normal human being except that it lacks free will." It's obvious that I have failed to acknowledge that whether we have free will is moot. The philosophical zombie idea is introduce just like this, but no one seems to notice the failure to acknowledge that it is moot whether we have consciousness. Philosophical zombies are "consciousness zombies" which are analogous to my "free-will zombies". It seems that the problem is that people are generally aware that some doubt that humans have free will, but they are not aware that some doubt that humans have consciousness (in the qualia-having sense).
So my question is, does the philosophical zombies question/idea contain a hidden assumption?
In light of this Meta answer: https://philosophy.meta.stackexchange.com/a/5470/58715 I have prefixed "(Why)" to the title of this question and have added to the body of the question, under the dashed line, some text.
I have convinced myself that there is no doubt that there is a hidden assumption in every presentation of the zombie question that I've looked at, including that of SEP, Wikipedia, and Chalmers' own website and so I have decided to focus the scope of the question on what seems a more interesting question, which is "Why is the assumption inherent in the zombie question hidden?"
I might as well add here another analogous question that shows how outrageous it is that the assumption in not acknowledged. Wikipedia, to its credit was the best out of the three in this regard, as you can read above, but even there the acknowledgement was buried in the body of the long article.
Imagine that I asked, "Is it conceivable that in our universe there could exist a philosophical zombie cat, meaning a cat that is the same in every respect as a normal cat, down to the last atom, except that it has no consciousness. It is dark inside. There is nothing it is like to be that cat." There's an assumption that ordinary cats are conscious. It would be interesting to put this question to people and see whether they notice or object to assumption hidden in it. It would be interesting to try out the zombie idea switching out humans for chimps, dogs, cats, crocodiles, snakes, sharks, and so on right down to bacteria and maybe viruses and even DNA molecules.
In the original version of this question I posited switching out free will for consciousness in the zombie question. This tactic could be combined with substitution of dogs and so on, to make the question "Could a kind of dog be conceived of that is the same as a normal dog except that it doesn't have free will?"
It's hard to believe Chalmers and SEP haven't heard about illusionism (or "consciousness illusionism" if you want to distinguish it from free-will illusionism which is a rarely-heard term for an unrelated and much older and well-known idea that says free will is an illusion i.e. does not exist despite the unshakeable subjective impression that it does.)
So my question is, does the philosophical zombies question/idea contain a hidden assumption and why (if/because it does) is this assumption (that normal humans are conscious and have qualia) not explicitly stated when the zombie question is asked?