What Is It Like to Be a Bat? 50 Years On

Thought Experiments [Part 4]

There is something that it is like to be you.

Right now, you are reading these words. While reading these words, you might be holding a warm cup of coffee. If so, there’s something it feels like to hold that cup. And there’s something it feels like to taste that coffee.

But what about the coffee? Imagine being the coffee.

Finding it difficult to imagine? Are you thinking there isn’t anything it is like to be a coffee?

This week, we’re discussing one of the most famous papers in philosophy: Thomas Nagel’s 1974 classic, What Is It Like to Be a Bat?

The timing couldn’t be better! Yes, it’s Halloween time! And everyone knows Halloween means bats.

But this month also marks exactly 50 years since Nagel first asked us to imagine what it’s like to be a bat. To celebrate this anniversary, Nagel has just published a new book by the same name.

Given how influential Nagel’s bat paper has been in the philosophy of mind and the cognitive sciences, it’s worth taking some time to understand it. So, this article starts a mini three-part series on Nagel’s ideas about bats. In Part 1 (that’s this article), we’ll focus on Nagel’s original bat paper. Next week, in Part 2, we’ll focus on how and why Nagel’s argument has been misinterpreted over the years. And in Part 3, we’ll take up Nagel’s invitation to explore the neuroscience behind human echolocation and ask whether it brings us any closer to knowing what it is like to be a bat.

Most people know Nagel’s bat paper because it’s the one where Negal defines consciousness in the following way:

… an organism has conscious mental states if and only if there is something that it is like to be that organism — something it is like for the organism.

This definition has become so popular that the term ‘what-it-is-likeness’ has become synonymous with consciousness.

If you’ve been following along with our larger series on thought experiments in the philosophy of mind, you’ll know we’ve been examining thought experiments that tackle the mind-body problem — that tricky question of how consciousness relates to the physical world. We started with philosophical zombies, then moved on to disembodied pain. Both of these thought experiments used conceivability arguments to challenge physicalism.

But now we’re shifting gears. The next few thought experiments in the series, starting with Nagel’s bat, take a different approach. Instead of asking what we can imagine, they ask what we can know about consciousness.

Nagel asks can we ever truly know what it’s like to be a bat? And if not, what does that tell us about consciousness?

At its core, Nagel’s bat paper is an attack on physical reductionism — the idea that conscious experiences can be completely explained by physical processes in the brain.

He makes three main points to build this argument.

1. We can’t know what it is like to be a bat.

2. There’s a difference between the subjective and the objective.

3. Objective science can’t tell us what it is like to be a bat.

Let’s take each point in turn. For each point, we’ll review Nagel’s claim and then look at what other philosophers have argued against that claim.

Point 1: We Can't Know What It Is Like to Be a Bat

Imagine being a bat.

Imagine flying around in the dark. While you can see, to figure out where to go, you mostly use sound — not sight. You echolocate. You make high-pitched squeaking sounds, and you use the echoes of these squeaks to know where you’re going. These echoes tell you not just where things are but their size, shape, and even texture.

Are you imagining what it would be like to be a bat? Or are you imagining what it would be like for you to behave as a bat behaves?

To imagine what it is like to be a bat, you have to imagine not just doing what bats do; you have to imagine experiencing what it is really like to be a bat.

Pretty difficult, right?

Nagel argues that imagining what it is like to be a bat is not answering the question we want to answer. We want to know what it is like for a bat to be a bat. If we try to imagine what it is like for a bat to be a bat, we run into the limits of our own mind — we don’t have the type of mind that could know.

If we could add bat-like knowledge to our human brain — like plugging in a new module. Would we understand what it’s like to be a bat? No. If that were possible, it would only give us a human understanding of what it is like to be a bat.

To truly know what it’s like for a bat to be a bat, we’d need to adopt the bat’s point of view.

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So, what would that involve? Presumably, we’d need a bat’s brain, receiving input from bat ears, bat wings, and all the other bat body parts. In other words, we’d need to become a bat, literally. But if we did become a bat, we’d no longer be human. Does that mean we would no longer understand what it’s like for a human to be human?

Objection: We Can Know What It Is Like to Be a Bat

Nagel had good reason to choose bats for his thought experiment. As mammals, they’re close enough to us that most of us think bats are conscious. But, Nagel reasoned, their ability to echolocate seems so different from anything we humans know that we will find it difficult to imagine what it is like to be a bat.

But, even as Nagel concedes, his example might not be as powerful as he intended. Humans can and do echolocate. Most of us do it without realising it.

Have you ever noticed how a bathroom can sound different from a living room? Or how you can tell if you’re in a large empty space even with your eyes closed? That’s because you use sound waves bouncing off surfaces around you to know something about the room you’re in. You echolocate. We don’t usually pay much attention to this ability — probably because we’re so reliant on our eyes. But the ability is there.

Some blind people have developed the remarkable ability to make clicking sounds with their mouths and use the echoes of those sounds to detect obstacles, determine the size and shape of objects, and even ride bicycles.

Of course, human echolocation isn’t a replication of what it is like to be a bat. But the fact that humans can echolocate at all suggests something interesting about Nagel’s argument.

In the body of the paper, Nagel makes strong claims that we can’t know what it is like to be a bat. But in footnote 8, we find a curious statement that seems incompatible with this claim. He states, ‘My point, however, is not that we cannot know what it is like to be a bat.’ He suggests that we might be able to know partially. We might be able to use our experience of echolocation as a step to understand what it’s like to be a bat, at least conceptually — more on what that might mean next week.

Knowing what it is like, he argues, might not be an all-or-nothing proposition. Instead, knowledge of what it is like might fall on a continuum.

The interesting thing about continuums is that movement along them typically represents differences in degree, not differences in kind. Each of us, supposedly, falls somewhere on the continuum between a complete understanding of what it would be like to be a bat and complete ignorance about what that would be like.

For example, someone who has learned to echolocate might be closer to the complete understanding end of that continuum than someone who’s never heard of a bat. Presumably, if knowledge of what it is like to be a bat falls on a continuum, more knowledge and experience should move us closer to knowing what it is like to be a bat.

We’ve learned a thing or two about bats and echolocation since 1974.

The question is, has this new knowledge brought us any closer to knowing what it is like to be a bat?

Nagel does not deny that we might move further along the continuum by gaining new knowledge. But at the same time, he famously suggests that this type of knowledge will, in the end, leave something out — the subjective point of view of the bat. The subjective perspective of the bat, according to Nagel, is something real or essential about what it is like to be a bat that no amount of progress along the continuum will fully capture.

A critic might ask what exactly Nagel means by viewpoint here. After all, if understanding what it is like to be a bat falls on a continuum of knowledge, where along that continuum does this elusive bat perspective emerge?

One concern is that Nagel is smuggling in the pesky homunculus — the idea of a little person inside our head who experiences the experiences. A reductionist might suggest that Nagel’s challenge is not that we can never know what it is like to be a bat but, rather, that we can never know what it is like to be a bat homunculus.

In Part 2 of this mini-series, we’ll return to some of the points raised here, including what Nagel means here by the word know. In Part 3, we’ll explore human echolocation and ask what that might tell us about what we can know.

Point 2: The Subjective-Objective Gap

Nagel’s second point follows from his first. It is here that he makes a crucial distinction between subjective and objective facts:

For if the facts of experience — facts about what it is like for the experiencing organism — are accessible only from one point of view, then it is a mystery how the true character of experiences could be revealed in the physical operation of that organism. The latter is a domain of objective fact par excellence — the kind that can be observed and understood from many points of view and by individuals with differing perceptual systems.

What Nagel is arguing here is that there are special kinds of facts — ‘facts of experience — facts about what it is like for the experiencing organism’.

These what-it-is-like facts can only be known through experiencing them firsthand. To know what it’s like to be a bat, we need to experience it from the bat’s particular point of view.

This, Nagel thinks, creates a puzzle: physical facts — facts about the physical operation of an organism — are objective. They are facts that can be observed and understood from many different viewpoints. A human scientist and a Martian scientist could both study and understand a bat’s brain and bat behaviour.

But facts about what it feels like to be a bat are subjective. Subjective facts can only be understood from the bat’s point of view.

Objection: There is No Subjective-Objective Gap

The main objection to Nagel’s second point was initially raised by Laurence Nemirow and developed further by David Lewis.

They suggest that Nagel makes a mistake when he defines knowing what it is like as gaining certain facts — special facts that can only be known from the subjective point of view. Nemirow and Lewis argue that knowing what something is like isn’t about acquiring special facts. It’s not even about acquiring information. Knowing what it is like is about gaining abilities.

Vegemite is an Australian food spread. It’s made from leftover brewers’ yeast extract. And unless you grew up in Australia, you probably have never tasted it. If you were to try it, what would you learn?

According to Lewis, when you taste Vegemite for the first time, you don’t learn some mysterious, phenomenal facts. Instead, you learn a new ability. You learn the ability to remember what Vegemite tastes like, to imagine it again, and to recognise it if you encounter it in the future.

This might sound like a subtle distinction, but it could have big implications for Nagel’s argument. If Lewis is right, then there are no special bat-consciousness facts that we’re missing out on by not knowing what it is like to be a bat. We just lack certain abilities. We simply don’t have the ability to remember, imagine, or recognise what it’s like to echolocate the way bats do.

But not having abilities is not all that surprising. Or philosophically earth-shattering!

We know that some people have abilities that others don’t. I can’t wiggle my ears. Maybe you can. No amount of information or facts will help me to wiggle my ears. I simply don’t have the ability to do it. My inability to wiggle my ears is simply due to my physical makeup — perhaps something to do with my particular ears and muscles.

Similarly, the argument goes, some creatures can echolocate, and others can’t. No amount of bat facts will allow us to imagine echolocating like a bat. But that doesn’t mean there’s anything mysterious going on. Just as the ability to wiggle ears or echolocate depends on physical features, so too does the ability to remember, imagine, and recognise experiences — it’s all about our physical make-up — how our brains and bodies work, not about whether or not we can know special types of facts.

Point 3: Science Can’t Tell Us What It Is Like

Imagine you’re having a drink of water with your scientist friend.

You say, ‘Ah! water, the wet, liquidy thing we can’t live without!"

And your know-it-all scientist friend replies, ‘Well, sure, that’s how it seems to you, but let me tell you — water is really a chemical compound consisting of two hydrogen atoms and one oxygen atom’.

You realise your friend might need to work on their conversation skills, but you also recognise they’re revealing something important about how science works. Science likes to take what seems to be true (subjective appearances) and move toward understanding what things really are (objective reality). Science tries to move away from explaining things from a specific point of view. It tries to see the world from the view from nowhere.

And usually, this works great! For almost everything science tries to study, we understand it better when we move from the subjective to the objective. We understand water better because we moved from the subjective seeming (water is a wet, liquidy thing) to objective facts (H₂O).

But Nagel argues consciousness is different. Consciousness just is the seeming.

This, Nagel reasons, creates a bit of a problem for the reductionists who are looking for an objective scientific explanation of consciousness. Science works by moving away from the subjective points of view toward objective facts. But consciousness is inherently subjective — it’s always tied to a particular point of view.

As Nagel puts it:

If the subjective character of experience is fully comprehensible only from one point of view, then any shift to greater objectivity — that is, less attachment to a specific viewpoint — does not take us nearer to the real nature of the phenomenon: it takes us farther away from it.

If physical reductionism is true, conscious experiences, like the experience of what it is like to be a bat, should be able to be explained objectively. But that, Nagel thinks, seems to be impossible. It seems that the only way for us to know what it is like to be a bat is to take the subjective standpoint of the bat.

And, the argument goes, this is exactly the mistake scientists make when they try to explain consciousness. They talk about neurons firing, chemical processes, and oscillations in the brain. They move towards the objective, as science does. But in doing so, they abandon the very thing they’re trying to explain — the what-it-is-likeness.

Objection: We Can Use Science to Know What It Is Like

Philosopher Kathleen Akins questions whether Nagel is making an implicit assumption here. She wonders whether Nagel assumes we can have pure feelings that are separate from what those experiences are about.

Akins’ argument can be a bit tricky, so let’s look at an example.

When you see a red apple, you might think you can separate that experience into two things — the pure feeling of redness and what that redness tells you about the apple (that it’s a ripe apple, that it’s not a green apple, etc.).

But Akins argues this is an illusion.

Try it next time you find yourself with a red apple. Try to experience just the pure experience of redness stripped away from everything about the apple. It’s a very difficult task. Even when you try your hardest to focus on the red sensation, you’re still experiencing it as the redness of something. The redness is always telling you something about the world.

This, Akins argues, creates a big problem for Nagel’s argument about bats.

By claiming that we can’t know the feeling of what it is like, Nagel is claiming that there is a pure feeling — or qualia — that is separate from the content of that experience. And it is this qualia that we cannot know.

But Akins argues that we can’t separate our experiences into two parts: the pure feeling on one side and what that experience represents or means on the other. When we hear an echo in a hallway, for example, the experience isn’t split into a pure feeling of the echo plus our understanding of what that echo tells us about the space. Rather, the way it feels to hear that echo is part of what that echo means.

Applying this to bats, Akins suggests that the what-it-is-likeness of bat echolocation can’t be divorced from what echolocation does for the bat — how it helps the bat detect objects, judge distances, and navigate its world.

If she’s right, we can learn about bat consciousness by studying bats scientifically. If what echolocation feels like cannot be separated from what it does for the bat, understanding what echolocation does for the bat gives us some insight into what it would feel like to be a bat.

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Next Week…

As we’ll see next week, Nagel’s famous bat argument has been misunderstood in several interesting ways. Some philosophers argue that even the objections we’ve looked at today miss the point. But the question is — do they miss Nagel’s actual points, or are they missing what others have assumed Nagel’s points to be? That’s the puzzle we’ll try to untangle next week.

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