# Zombies! Substance Dualist Zombies?

Introduction
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In the classical [Zombies! Zombies?](https://www.lesswrong.com/posts/fdEWWr8St59bXLbQr/zombies-zombies) post, Eliezer has thoroughly analyzed the so called Zombie Argument and demonstrated its absurdity. So what else can even be said here? Case closed.

Well, not so fast. Apparently, a lot of people, [including David Chalmers himself](https://www.lesswrong.com/posts/fdEWWr8St59bXLbQr/zombies-zombies?commentId=5qKe5gQ8HWgfRq9Dw), still manage to take the argument seriously, even though they are familiar with Eliezer's analysis. They believe that Eliezer only argued against a weak - Epiphenomenalist - version of Zombie Argument. But that there is also a stronger Substance Dualist version of it, that is not refuted by Eliezer's reasoning.

In this post we will analyze this version of the argument and use it as a practical exercise for aspiring rationalists.

Understanding the Substance Dualist Zombie Argument
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According to Zombie Argument:

*The existence of a Zombie World - a universe completely physically identical to ours, but where humans do not have consciousness - is logically possible.*

*Therefore, consciousness is not physical.*

Regardless of whether the argument is sound or not, it's clear how one can believe in it, while being an epiphenomenalist. A universe, where all physical causes and effects play exactly the same as in ours, and yet there is no consciousness, is consistent with the belief that consciousness is causally inert. 

$Causality(Consciousness) = 0$

$Causality(Physics, Consciousness) = Causality(Physics)$

But how can one possibly subscribe to this argument, while being a substance dualist and, therefore, accepting that consciousness has actually causal effect on the universe? Isn't it an obvious contradiction? 

If the combined causal effect of physics and consciousness together lead the world to some state and consciousness has non-zero causal effects on the state of the world, clearly, removing consciousness will lead to world being in a different physical state!

$Causality(Consciousness) ≠ 0$

$Causality(Physics, Consciousness) ≠ Causality(Physics)$

Substance Dualists agree with these equations. However, they say, the causal effects of the consciousness in our world can be accounted for in the Zombie World by a difference in its laws.

Haven't we gone through it already? In such a case the symmetry between the two worlds will be ruined! We will be talking about a [Zombie Master](https://www.lesswrong.com/posts/fdEWWr8St59bXLbQr/zombies-zombies) scenario, where physics of the zombie world is different in a compensatory way so that together with the lack of consciousness it arrived to the same state as our world:

$Causality(Consciousness) ≠ 0$

$Physics  ≠ Physics'$

$Causality(Physics, Consciousness) = Causality(Physics')$

No, no, say the substance dualists, there is another way. The compensatory laws can themselves be *non-physical*.

$Causality(Consciousness) ≠ 0$

$Causality(Physics, Consciousness) = Causality(Physics, NonPhysics)$

Therefore, the symmetry between two worlds is preserved and substance dualism satisfies the premise of Zombie Argument. 

And as it is not based on the fact that consciousness is causally inert, it's completely unharmed by Eliezer's critique. Can you imagine how blatantly arrogant Eliezer was to think himself so much smarter than all the philosophers who treat the Zombie Argument seriously? All this time he was dismissing it as ridiculous, while ignoring a half of it! A mistake that a sophomore philosophy student wouldn't make!

Your Power as a Rationalist
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If you feel incredibly annoyed by this line of reasoning - so was I. There is something that feels fundamentally unfair about this whole predicament.

There are infinite ways to produce faulty reasoning about a matter, and only one way to produce the correct reasoning. So you can spend hours, even days, comprehensively debunking an argument, trying to cut it off at every possibility, building a clear and coherent model, free of any traces of confusion, so that anyone could be able to understand it. And then someone uses a clever semantic trick and simply declares that some causal forces of the universe are *non-physical,* therefore circumventing all your criticism.

This just shouldn't be allowed. You can't treat *physics* as an arbitrary category border around some laws and not the others. It's not what the term *means*. But good luck explaining it through the inferential distance to philosophers, who were specifically trained to play semantic games and do [modal reasoning](https://www.lesswrong.com/posts/vzLrQaGPa9DNCpuZz/against-modal-logics) and think that it's a respectful occupation and a proper way to find truth.

And so one may even feel that philosophy is hopelessly doomed to be eternally confused. That it's useless to even try to engage with this diseased discipline.

If you feel this way, I, once again, empathize with your annoyance, but not with your despair. Remember the basics. [Truths are entangled and lies are contagious](https://www.lesswrong.com/s/GSqFqc646rsRd2oyz/p/wyyfFfaRar2jEdeQK). Every mistake in reasoning imposes a cost. Every misstep in a dance of rationality is revealing. You may try to hide one mistake by another, but this is only going to make your inevitable downfall more devastating.

Remember your power as a rationalist. Focus your uncertainty and pay attention to your confusion. If you know that something shouldn't work, then it probably doesn't. And if you know what the mistake is, then you've already done the most important part of the work. The last part is easy: to show the absurdity that follows.

Rationality is supposed to win. Not just among people who are reasoning clearly but also among those who got lost in confusions of conventional philosophy. Correct reasoning should be able to cut through them like a knife through butter.

An average aspiring rationalist who has read the sequences should be able to show themselves the absurdity of Substance Dualism Zombie argument. I recommend everyone to attempt to think about the problem for at least five clock minutes before reading further, where I'll give more hints and eventually reveal the answer.

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Comparing the Two Arguments
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If the Substance Dualist Zombie Argument hides the flaw of the Epiphenomenalist one, via making another reasoning mistake, then it introduces an extra cost. What is it? Let's compare the arguments and find out.

The Epiphenomenalist version is based on the assumption that consciousness doesn't have causal influence on the universe. The Substance Dualist version is not based on it. This is what allows it to evade Eliezer's critique. But not making a particular assumption cuts both ways - yes, your argument doesn't suffer if this assumption is shown false, but neither do you get the benefits this assumption contributed to the argument in the first place.

So what is the point of this assumption, in the first place? What does it contribute to the argument? Once again I recommend you to think for yourself, if you haven't figured it out already.

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It presents a principled way to draw a category border between Physics and Consciousness.

If consciousness doesn't play any causal role in the universe, but still is a real phenomenon, then it's very special, therefore it's quite natural to put it into a category of its own. Being able to separate everything in the universe into things that have causal influence and things that do not have causal influence is enough to present the Epiphenomenalist version of the argument:

$Causality(Consciousness) = 0$

$Causality(Physics, Consciousness) = Causality(Physics)$

On the other hand, to formulate a Substance Dualist version of the argument we need a much more powerful ability - to draw a category border between Physics and Non-Physics in an arbitrary, gerrymandered way. 

$Causality(Consciousness) ≠ 0$

$Causality(Physics, Consciousness) = Causality(Physics, NonPhysics)$

The exact thing that annoyed us in the first place. And this thing has truly absurd consequences.

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Okay, I think I've given as many hints as I could give without spoiling the answer directly. This is your last chance to solve the mystery yourself, if you haven't done so already. 

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And the Answer Is...
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Consider this modification of the Zombie argument:

*The existence of a universe completely physically identical to ours, but where there are no electrons - is logically possible.*

*Therefore, electrons are not physical.*

The structure of the argument is the same. But surely the premise here is clearly wrong? How can we have a universe with the same physics and causality but without electrons?

Well...

$Causality(Physics, Electrons) = Causality(Physics, NonPhysics)$

The same trick that Substance Dualist Zombie Argument does, can be applied here as well. If one can draw an arbitrary category border around one causal part of the universe, one likewise can do it with another.

And lo and behold, we can conceptualize a Zombie-Electron universe with the same physics, the same causal effects, but without electrons, because the causal effects of electrons are accounted for by non-physical laws of this universe. 

This should be enough to demonstrate the absurdity of the Substance Dualist Zombie Argument. We've just applied the same method that proves non-physicality of consciousness, to prove a clearly wrong conclusion, therefore the method is flawed.

But let's move a bit further, for the sense of poetic justice.

The general structure of the argument

$Causality(Physics, X) = Causality(Physics, NonPhysics)$

Doesn't depend on what exactly we mean by $X$. Therefore, conditionally on the Substance Dualist Zombie Argument being sound, we can prove that literally anything is not physical, which in the end leads us to a curious conclusion:

$Causality(Everything) = Causality(NonPhysics)$

Here we've "outsourced" all causal effects of the universe to the sphere of the non-physical. Therefore, Substance Dualism collapses. We've just "proven" that either Idealism is true or matter is causally inert.

But remember, we've assumed no principled distinction between $Physics$ and $NonPhysics$ labels. For the sake of this argument, they refer to two mutually exclusive but totally arbitrary category borders around causally active stuff. So there is no reason why we can't simply switch the labels:

$Causality(Everything) = Causality(Physics)$

Therefore, either physicalism or epiphenomenalism is true. But the latter possibility is already discarded:

$Causality(Consciousness) ≠ 0$

And so, we've just used Substance Dualist Zombie Argument to "prove" that physicalism is true.

The reason why we can use the same argument to "prove" three mutually exclusive views: substance dualism, idealism and physicalism is, of course, because [falsehood implies everything](https://en.wikipedia.org/wiki/Vacuous_truth). As the core premise of Zombie Argument is flawed, with enough creativity we can twist it however we like, arriving to any conclusion.

So at this point it should be very obvious that something is deeply wrong with the Zombie Argument. But where exactly the mistake lies? And how did it manage to confuse people for so long? What cognitive algorithm produces this kind of mistakes and how can we not repeat them in the future? These questions will be addressed in the next post.