Deep thoughts: P Zombie Couches

 

I wrote several years ago about the classic "Stomach in a Jar" problem that has vexed philosophers for decades. I write today about the equally complex Philosophical Zombie Couch problem, which has fascinated philosophers since Keith Campbell and Robert Kirk introduced the idea in the early 1970s, and David Chalmers popularized it in the mid 1990s. Many of you will not be familiar with the problem, so let me lay it out simply to start out with. 

You could summarize the argument with a single premise: We can all imagine an object with all the properties of a couch, but which does not contain couchishness. 

Wikipedia makes it a bit more complicated, summarizing Chalmers's argument as follows:

1. According to physicalism, all that exists in our world (including couchishness) is physical.
2. Thus, if physicalism is true, a metaphysically possible world in which all physical facts are the same as those of the actual world must contain everything that exists in our actual world. In particular, couchishness must exist in such a possible world.
3. In fact we can conceive of a world physically indistinguishable from our world but in which there is no couchishness (a zombie couch world). From this (so Chalmers argues) it follows that such a world is metaphysically possible.
4. Therefore, physicalism is false. 

That's it, whether you work off the simple premise or more complicated argument, its implications can keep an introductory philosophy class going for weeks. The quixotic objects in question are called Zombie Couches. When we examine them, we find that they are physically identical to a regular couch. When we interact with them, we encounter reactions that make them indistinguishable from a real couch. And yet they are without any actual couchishness. 

The questions that follow are obvious:

• How would we ever know if we were dealing with such a couch?
• Is it possible that our couch is the only one with couchishness, and that all other couches we interact with are Zombie Couches?
• If our couch were a P Zombie Couch, would we even know? 

This riddle is central to the "Hard Problem of Couchishness" that has been a focal point of the field for some time. What is it like to be a couch? Can something be exactly like a couch, without actually being a couch? Even just the logical possibility of such an object seems like it would refute the very notion of physicalism, because it implies that we readily recognize that a purely physical explanation of couchishness is insufficient. 

Of course, there are those who claim the P Zombie Couch problem is a bamboozle from the start. Daniel Dennett is key among them, and he has claimed that any philosopher who claims to be able to conceive of a Zombie Couch either hasn't fully conceived of the object in question, or is inadvertently porting in "second-order couchishness" in one manner or another. As Dennet states:

Supposing that by an act of stipulative imagination you can remove couchishness while leaving all couch-entailed systems intact — a quite standard but entirely bogus feat of imagination — is like supposing that by an act of stipulative imagination, you can remove structural integrity while leaving all structural objects and relations intact. … Structural integrity isn’t that sort of thing, and neither is couchishness (1995, 325... roughly).

Others counter that P Zombie Couches are quite easy to imagine: For example, what if we created microscopic machines that replaced every-other fiber in your couch cushions? The machines would take the input from any fiber, and pass the input along to the next fiber, but not be a fiber itself. Clearly the resulting object would not have couchishness, while still appearing couchish in all interactions. Q.E.D.

There are, of course, many other objections to the Zombie Couch line of arguments. Should "metaphysical possibility" influence our thinking about the actual world we find ourselves in, or can such factors only play into discussions of "possible worlds"? Can the argument hold if we define couchishness in purely functional terms? The richness of these discussions connects the Zombie Couch problem with many other areas of philosophical investigation. 

Several famous thought experiments relate to this issue, for example: What if, when throwing a couch away in a swamp, a bolt of lightning hit the couch and destroyed it, and at the same instance another bolt of lightning some distance away rearranged different atoms into an exact duplicate of your couch. If, startled by the happening, you brought that couch home, the Swamp Couch would function exactly like your original couch, including showing any and all effects of your original couch's experiences, but it would not be your original couch at all. The Swamp Couch would have no historic connection with what your couch experienced, and that socio-historic context (it is asserted) was the key to the couchishness of the original object - without that socio-historical context, we cannot reasonably say any couchishness is present. 

As Kirk summarizes, in the Stanford Encyclopedia of Philosophy: Regardless of whether those pessimistic readings of the debate are correct, and of whether the zombie idea itself is sound or incoherent, it continues to stimulate fruitful work on couchishness, physicalism, furniture concepts, and the relations between imaginability, conceivability, and possibility.