David Egan Philosophy

It’s spooky season. If you’ve recently encountered zombies and ghosts, werewolves, vampires, and swamp creatures, you may have been out on the streets with trick-or-treaters. Or maybe you were in a philosophy seminar.

The zombies of horror films tend to be lumbering creatures with decaying flesh and a hunger for human brains. Easy to spot and important to avoid. Philosophical zombies, by contrast, aren’t dangerous but they’re also indistinguishable from normal human beings.

A philosophical zombie is a being that has all the physical characteristics of a human being but lacks conscious experience. The walk like you, they talk like you, they laugh and cry like you, but there’s nothing going on inside.

These imagined beings highlight a puzzle about the nature of consciousness. There doesn’t seem to be any obvious connection between the physical stuff that goes on inside of us—the firing of neurons and all that business in the brain—and the conscious experience it allegedly gives rise to. We can tell a rich and detailed story about how neuron firings in the brain innervate muscles that lead to physical phenomena like walking, talking, laughing, and crying without at any point needing to invoke conscious experience as a cause for any of it. Some philosophers argue that consciousness is an “epiphenomenon”: a byproduct of brain activity without any causal role.

If it’s possible to explain all of my behaviour without reference to my conscious experience, does that mean I am, to all outward appearance, indistinguishable from zombie-David? Is there any principled way I can be certain that the people around me have conscious experience and aren’t themselves zombies?

Philosophical zombies have a prominent place in philosophical debates between physicalists and dualists in the philosophy of mind. Physicalists maintain that a physical description of the brain can tell us everything there is to know about the mind while dualists argue that there has to be more to the story than that. Zombies first enter the philosophy literature in a 1974 paper by Robert Kirk and reach their most famous and rigorous development in the work of David Chalmers.

Both Kirk and Chalmers deploy zombies as an argument against physicalism. If zombies are conceivable, Chalmers argues, then they’re possible. And if zombies are even possible in theory, then we’re able to distinguish between zombies and non-zombies even though they’re physically indistinguishable. And if that distinction is possible even in theory, Chalmers argues, physicalism can’t give us the whole story about consciousness.

Ghosts enter the philosophical literature as the inverse of zombies. Zombies have human bodies but no minds. Ghosts have human minds but no bodies.

The most famous reference to ghosts in the philosophical literature comes in a disparaging form. Gilbert Ryle characterizes the dualism of René Descartes as positing a “ghost in the machine.” Descartes was a substance dualist: he maintained not only that the physical facts don’t tell the whole story about the human mind but that minds constitute a distinct kind of substance that exists apart from and alongside matter. Ryle thought the idea of the mind as a distinct kind of stuff in the universe was a deeply misguided notion that had had a baleful influence on much subsequent thinking about the mind. He coined the term “category mistake” to explain what’s wrong with treating the mind as a special, ghostly kind of thing.

Werewolves and vampires illustrate philosophical edge cases concerning human agency. Werewolves pop up occasionally as examples of human beings who lack rational self-control. The idea of the human soul as divided between rational and non-rational impulses dates back to Plato and Aristotle. As they figure it, human rationality is always in a struggle with animal impulses within us. Plato describes the “beast within” that can take us over when we lose rational control. Neither of them mentions werewolves explicitly—despite the fact that the Histories of Herodotus, with which they would have been familiar, contains one of the earliest written references to werewolves. But the figure of the werewolf sometimes enters discussions of the will when contemporary philosophers describe the predicament of a person overtaken by appetite.

In contrast to werewolves, vampires have all the rational control of a preening European aristocrat—but they exercise this rational control in the service of ends that seem monstrous to us. L. A. Paul invokes vampires as a key case in her influential treatment of transformative experience. Suppose you were presented with the option of being irreversibly transformed into a vampire—should you take it? Rational choice theory instructs us to weigh up the pros and cons based on what we know and what we value. The problem with the vampire case, Paul says, is not simply that we can’t know what it’s like to be a vampire without actually becoming one, but also that becoming a vampire will change our values. Things we consider horrific would come to seem attractive and some of the things we cherish would have no value to our vampire selves.

As a result, it’s not clear that we can make a rational decision about whether or not to become a vampire. Paul argues a number of less horrific possibilities—like having a child or converting to a religion—have a similar structure. These are transformations that change not only your circumstances but also your sense of what matters. If a decision promises to change your values, how can you rationally assess it based on the values you have now? Vampires stand as a paradigm for a fundamentally altered way of inhabiting the world.

Lastly, the Swampman enters the philosophical funhouse of horrors thanks to Donald Davidson. He hypothesizes an unfortunate lightning strike in a swamp that vaporizes him while also simultaneously reconstituting the matter in a nearby dead tree so that the dead tree becomes a perfect replica of the Davidson that was. This newly constituted Swampman would look like Davidson, talk like Davidson, and be able to describe in detail all of Davidson’s previous philosophical work.

But, Davidson argues, this Swampman couldn’t truly be said to have thoughts or even to be using words meaningfully. For the firings of neurons in our brains and the sounds that come out of our mouths to count as thoughts and words they have to be about something, and that aboutness—“intentionality” in philosophy jargon—requires not just the movement of matter but a causal connection to thoughts and words that have come before, and the people and social contexts that produced them. The fact that Swampman’s utterances sound like things Davidson might say is the result of a stupendous coincidence of physics and chemistry. But just as word-like whistling of the wind doesn’t mean the wind is “talking,” Swampman, too, can’t be said to be thinking or speaking.

Why does this house of horrors find its way into often very technical work in philosophy? Scientists are concerned with what’s possible in nature but philosophers are concerned with what’s conceptually possible. It might be that, in the natural world as we know it, minds and bodies always go together. But can we conceive of them apart? If so, what does that tell us about what minds and bodies really are?

The creatures that populate horror stories often violate our understanding of the natural order of things. In the context of a story, these violations can be deeply unsettling: if such creatures exist, the world as I thought I knew it makes less sense than I supposed. But these violations can be productive grist for the philosophical mill. By pushing beyond what is the case to questions about what could possibly be the case, philosophers work to understand the essential features of reality. 

1. In the 2024 general election, Britain’s Green Party won just 6.4% of the vote and 4 (out of 650) parliamentary seats. For all that, over 40% of Britons hold a favourable view of the Green Party, the highest rate for any major British political party. (source)
2. The Ship of Theseus is a famous philosophical puzzle concerning identity over time. It invites you to imagine a ship whose planks are gradually replaced over time until, after a while, no planks from the original ship remain. The question is then whether the ship is still the same ship as the original, and if not, at which point it ceased to be the original ship. As it happens, the Wikipedia page on the Ship of Theseus is a case in point. It’s been edited 2052 times since it was first published in 2003 and not a single sentence from the original Wikipedia page remains. (source)
3. The universe is expanding: all astronomers agree about that. But how fast it’s expanding is another question. There are two standard methods for measuring the rate of expansion of the universe. Both have been tested rigorously. And they give different results. No one is sure why. (source)
4. English has only a small number of loan words from Turkish and Turkic languages. I already knew about yogurt but I recently learned that the English “horde” derives from the Turkish “ordu,” meaning “army.” (source)
5. Frequent nightmares are a stronger predictor of premature death than smoking, obesity, poor diet, or sloth. (source)
6. Although the Norman conquest of Britain happened nearly a thousand years ago, it’s still the case that people in Britain with Norman surnames like Darcy or Glanville are likelier to be wealthy than people with Anglo-Saxon surnames like Smith and Cooper. (source)
7. Four in ten Palestinian men are imprisoned by the state of Israel at some point in their lives. (source)
8. Goalies in the National Hockey League wear elaborately painted masks. The trend of painting masks started in 1970 as a Halloween prank. Philadelphia Flyers goalie Doug Favell painted his mask orange in a tribute to the Great Pumpkin of Charlie Brown lore. (source)