Thomas Nagel: What is it Like to be a Bat?

Does consciousness arise from the brain? Do certain brain processes always give rise to certain conscious experiences? Or is the relationship between mind and matter more mysterious?

Some thinkers approach the relationship between consciousness and the brain with a reductionist mindset. Just as water can be described at the chemical level as H2O, genes in terms of DNA, and oak trees in terms of hydrocarbons, so conscious experiences can be described in terms of certain neuronal patternings.

We might not have it all mapped out quite yet, but science will ultimately reveal how and why consciousness is a product of underlying brain processes.

Many philosophers dispute this, however: in the case of consciousness, it is not clear that reductionist explanations can really give us what we’re after.

One of my favorite essays I studied as an undergraduate was Thomas Nagel’s paper, What Is It Like to Be a Bat?.

Since its 1974 publication, Nagel’s essay has become a mainstay for syllabuses on the philosophy of mind. It’s famous not only for its brilliant title, but also its tantalizing characterization of consciousness, which Nagel then wields to challenge reductionist approaches to the philosophy of mind.

“[A]n organism has conscious mental states,” Nagel writes,

if and only if there is something that it is like to be that organism — something it is like for the organism.

Nagel calls this the “subjective character of experience”. It is also known in the philosophical literature as qualitative experience, phenomenal experience, ‘raw feels’ and qualia.

The point about conscious experience is that there is something it is like for the experiencer to see x, hear y, or feel z, and it is through our subjective conscious experiences that we each know the world.

The problem for reductionist approaches is that it is not clear how physical descriptions of the brain can account for this subjective character of experience.

What is the conceptual link between this organization of neurons and, say, the taste of chocolate? Couldn’t the neurons just fire by themselves, without the need for an accompanying experience? Can’t we imagine philosophical ‘zombies’ who’d exhibit all the same brain activity and outward behavior as humans, yet feel no inner conscious experience?

(The philosopher David Chalmers later called this the ‘hard problem’ of consciousness: why is the brain’s whir of information processing accompanied by a felt experience, and what governs this relationship?)

We might think an explanation will emerge just with more research into the brain. But in his famous paper, Nagel argues we’ll likely need more than this; we’ll need an entirely new conceptual schema.

What is it like to be a bat?

To demonstrate the insufficiency of our current approach, Nagel asks us to consider the subjective experience of a bat. Most bats primarily perceive the world by a form of sonar, or echolocation, emitting rapid, high-frequency shrieks, and then navigating their environments according to the echo of those shrieks. This gives them a sense of distance, size, shape, motion and texture. We know this by observing bats and looking at their brains.

Bat sonar, however, is nothing like any of our senses. What would it actually be like from the inside to navigate the world in this way? As Nagel comments, “there is no reason to suppose that it is subjectively like anything we can experience or imagine”:

It will not help to try to imagine that one has webbing on one’s arms, which enables one to fly around at dusk and dawn catching insects in one’s mouth; that one has very poor vision, and perceives the surrounding world by a system of reflected high-frequency sound signals; and that one spends the day hanging upside down by one’s feet in an attic.

All of these imaginings would only indicate what it would be like for us to behave as a bat behaves. “But that is not the question,” Nagel writes. “I want to know what it is like for a bat to be a bat.”

Nagel’s point is not that humanity is incapable of ever discovering what it’s like to be a bat; it’s more that, right now, with our current reductionist approaches to consciousness, we have no way of moving from information about a bat’s brain to insight into the subjective character of its experiences.

We can imagine ourselves as bats, drawing on our own sensory capabilities, but we cannot imagine what it is like for bats to be bats, with their senses and brains.

From the brain to consciousness, we have no conceptual bridge, because it seems the subjective character of consciousness is necessarily tied to the subjective point of view of the experiencer. Indeed, Nagel asks:

what would be left of what it was like to be a bat if one removed the viewpoint of the bat?

The problem is that this confounds how we typically try to form an objective account of something.

Usually, the direction of travel in our explanations is to move away from higher-level, subjective points of view to consider more fundamental, ‘objective’ viewpoints — as with water to H2O, genes to DNA, and oak trees to hydrocarbons. We ‘reduce’ the higher-order appearance to a lower, more general level.

If we do this with conscious experiences, however, then we seem to be abandoning the very thing that we seek to explain:

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.

When it comes to consciousness, the subjective appearance is the reality we seek to study.

Suppose there were some superintelligent aliens who lacked vision, for instance. If they wanted to get at the subjective character of my experience of looking, they would have to somehow take up my point of view.

If instead they put me to one side, focusing only on the mechanics of the human eye and certain neuron firings in the brain, they’d lose the essence of my conscious experience. If they didn’t somehow incorporate my inner point of view, the subjective character of my experience would remain elusive and unreduced: all they’d describe is the physical processes correlated to it.

What does it mean to say that consciousness arises from the brain?

The conclusion of Nagel’s reflections is not to say it’s false that consciousness arises from the brain; it’s that we currently have no conception of how it could be true. The thesis that ‘conscious experiences are brain processes’ is equivalent to a pre-Socratic philosopher declaring that ‘matter is energy’: it might be true, but no background framework exists to make sense of it.

If we want to get clearer on consciousness, Nagel thinks we need not only more research into the brain but also a new conceptual schema.

How could the aliens go from describing my brain to understanding the quality of my experiences, for instance? How could we describe vision to someone who was blind from birth? How could we actually know what it’s like to be a bat?

In all these cases, a new set of concepts seems to be required to bridge the gap, and such concepts may be beyond what the human intellect is capable of.

Many philosophers have taken issue with Nagel’s paper since its publication.

Daniel Dennett claims the ‘what it is it like’ aspect of consciousness is a red herring, a ‘user illusion’ that can be explained away. P.M.S. Hacker suggests it’s a linguistic quirk: the ‘hard problem’ of consciousness is a conceptual confusion masquerading as an empirical problem. Others argue we can actually know more about a bat’s subjective experience than Nagel allows.

But Nagel’s What Is It Like to Be a Bat? essay remains hugely influential. If you have a spare twenty minutes, I’d recommend reading it in full (you can do so for free via the link).

In accessible language, Nagel manages to capture the mind-body mystery, the problem of other minds, and the limits of human reason. If you’re curious about the philosophy of consciousness, it’s a wonderful place to start.

What do you make of Nagel’s arguments?

• Do you think consciousness poses a unique problem to our standard models of explanation?
• How would you try to describe sight to a blind person? Is it possible to construct an imaginative language in this domain?
• Or here will we always run up against the limitations of what’s possible with human communication?

To inform your answers, you might enjoy the following related Philosophy Breaks:

• Do Neurons Push Thoughts Around? Or Do Thoughts Push Neurons Around?
• What is Consciousness?
• Why ‘Zombies’ Cause Problems for Brain Science and Consciousness
• Mind Chat’s Philip Goff and Keith Frankish On Why We Are Conscious
• Daniel Dennett: the Best 5 Books to Read
• Consciousness: the Best 5 Books to Read

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