Exclude the supernatural? My worldview is up for grabs.

I think the (very widely held) idea that consciousness is evidence that the world isn't purely material is founded on a mistake.

So the argument seems to go something like this. "Imagine a mind, or the nearest possible thing to a mind, made up entirely of material stuff. Can you see where its consciousness comes from? No? Why, then, clearly minds must be immaterial, or have immaterial components, or something of the sort."

But if you actually try to turn this into an argument that would convince someone who didn't already want to believe in immaterial minds/souls/spirits, you'll find that there's a huge gap in it. It purports to show that "minds are entirely material" (call this M) is less plausible than "minds are not entirely material" (not-M) by looking only at consequences of M and not comparing them with consequences of not-M.

If the argument had turned up an actual logical contradiction as a consequence of M, that would be fair enough: if M leads to contradiction then not-M must be better (unless M and not-M are both actually nonsense of some sort). But if M is merely improbable or counterintuitive or currently lacking good explanations, you can't compare M with not-M until you've also looked to see whether not-M has the same problems.

In this instance, it's quite true that it's hard to see how material stuff could give rise to the experience of consciousness. Fair enough. Is it any easier to see how immaterial stuff (or immaterial non-stuff) could do it? I don't think so. -- Other than by begging the question, the theist's favourite technique. You just say, e.g., that by definition souls give rise to consciousness, and then of course belief in souls "explains" consciousness. But of course this is simply cheating: there's no actual explanation there, nothing more than a bare baseless assertion. You could just as well say that by definition matter gives rise to consciousness when it's appropriately organized. Which would be daft, and materialists don't actually say that, but that's not a weakness of the materialists' position. (More often, the theist doesn't say in so many words "I define souls to be things that give rise to consciousness". They simply take that for granted, and no one notices because it's such a familiar move.)

The exact same sort of broken logical structure is found in typical theistic (or supernaturalist) arguments from free will and moral absolutes.

Free will is covered pretty extensively on this site, although as the wiki page suggests, it can be a useful experience to work out for yourself.

Moral absolutes are also addressed, but since I'm having trouble remembering the names of the articles, it's easier to simply ask; can you explain how we would observe the universe to be different if there were definitively no moral absolutes?

Consciousness is probably the least open-and-shut case of the three. Some reading is available here, but it might be quicker to deal with the question by asking this. Is the entirety of the consciousness contained in a supernatural entity? That is, is it an irreducible mental thing? If so, why does a person's mental state correspond so consistently to the physical state of their brain? If not, and the supernatural phenomenon merely translates the physical states into subjective experience, why suppose that something that doesn't follow the rules that every other known thing in existence does is the best explanation for this one thing, given that we've never found evidence of anything like that anywhere else?

Regarding morality. Systems can have properties that their parts alone do not. Morality is an objective property of a system that consists of a person that utters moral statements and the specific entity in, or feature of, the world that the statement identifies or denotes. Yet all all this can be explained in terms of lower level interactions. This does not contradict.

Regarding free will. Free will is a middleman. Consciousness between cause and effect. The intelligent refinement of causation into an effective agent. The sun at your back - your shadow in front. You are the shadow player. Nevertheless, to claim sovereignty is trying to get ahead of your own shadow. You imprint reality with a pattern of volition. But not without its implicit consent.

Some quotes that might highlight other problems, including consciousness :

Science is not in principle committed to the idea that there’s no afterlife or that the mind is identical to the brain (…) If it’s true that consciousness is being run like software on the brain and can – by virtue of ectoplasm or something else we don’t understand – be dissociated from the brain at death, that would be part of our growing scientific understanding of the world if we discover it (…) But there are very good reasons to think it’s not true. We know this from 150 years of neurology where you damage areas of the brain, and faculties are lost (…) You can cease to recognize faces, you can cease to know the names of animals but you still know the names of tools (…) What we’re being asked to consider is that you damage one part of the brain, and something about the mind and subjectivity is lost, you damage another and yet more is lost, [but] you damage the whole thing at death, we can rise off the brain with all our faculties in tact, recognizing grandma and speaking English!

— Sam Harris’ Argument Against the Afterlife

One compelling reason not to believe the standard-issue God exists is the conspicuous fact that no one knows anything at all about it. That’s a tacit part of the definition of God – a supernatural being that no one knows anything about. The claims that are made about God bear no resemblance to genuine knowledge. This becomes immediately apparent if you try adding details to God’s CV: God is the eternal omnipotent benevolent omniscient creator of the universe, and has blue eyes. You see how it works. Eternal omnipotent benevolent omniscient are all simply ideal characteristics that a God ought to have; blue eyes, on the other hand, are particular, and if you say God has them it suddenly becomes obvious that no one knows that, and by implication that no one knows anything else either.

— Ophelia Benson on divine hiddenness.

The most terrifying fact about the universe is not that it is hostile but that it is indifferent; but if we can come to terms with this indifference and accept the challenges of life within the boundaries of death — however mutable man may be able to make them — our existence as a species can have genuine meaning and fulfillment. However vast the darkness, we must supply our own light.

— Stanley Kubrick

What can we make of someone who says that materialism implies meaninglessness? I can only conclude that if I took them to see Seurat’s painting “A Sunday Afternoon on the Island of La Grande Jatte," they would earnestly ask me what on earth the purpose of all the little dots was.

— The scourge of perverse-mindedness

A man can do what he wants, but not want what he wants.

— Arthur Schopenhauer

More generally, many of the objects demonstrated to be impossible in the previous posts in this series can appear possible as long as there is enough vagueness. For instance, one can certainly imagine an omnipotent being provided that there is enough vagueness in the concept of what “omnipotence” means; but if one tries to nail this concept down precisely, one gets hit by the omnipotence paradox. Similarly, one can imagine a foolproof strategy for beating the stock market (or some other zero sum game), as long as the strategy is vague enough that one cannot analyse what happens when that strategy ends up being used against itself. Or, one can imagine the possibility of time travel as long as it is left vague what would happen if one tried to trigger the grandfather paradox. And so forth. The “self-defeating” aspect of these impossibility results relies heavily on precision and definiteness, which is why they can seem so strange from the perspective of vague intuition.

— Terence Tao, The “no self-defeating object” argument, and the vagueness paradox

It's important to note that talking about the world in terms of atoms and quarks is just using a particular language. The principle of Turing equivalence is relevant. (One weird idea is to talk about how many equivalent-of-bits it takes to specify the equivalent of Turing equivalence for the equivalent of a Turing language. "Analogy" is a cluster of confusing concepts!) Talking about souls isn't taboo, and in fact I find it useful sometimes. The important part is having an accurate model of the world such that you can make correct testable predictions, and in fact that's only important insofar as it helps you make correct decisions. Unfortunately, figuring out what "correct" means is an incredibly hard problem, and the language of moral absolutes is only so helpful. The important heuristic for using languages is to avoid the mind projection fallacy and instead remember that all maps can be inaccurate, including maps of maps.

If you want exposure to the best condensed version of coherent mechanical/redictionistic/scientific thinking about consciousness that I know about, watch Kristof Koch give a talk on the "Neural Correlates of Consciousness". This might help clear some things up?

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In things like Cartesian Dualism, mind stuff is supposed to have mental properties as essential and irreducible features. Cartesian minds, are , conroversially, "without moving parts". Surely that would make them low in complexity.

Be careful not to privilege the scientific prior, though. Somewhere between the inability to justify induction and the inability to justify your interpretation of the evidence is some tricky argumentation that might be flawed. E.g. in some ontologies there's an upper bound on the confidence you can have that we're not in an ironic tragedy written by God to mock all those who fall to the cunning of the transhuman called Satan and thus aspire to false knowledge. To a non-trivial extent violating the laws of physics only has high K complexity if you assume the conclusion that it has high K complexity.

You'll notice that a lot of LW is focused on working with and understanding the parts of your mind that are not clearly and obviously rational.