What is it like to be a bat?
A bat perceives the world by echolocation. However much we learn about its brain, we may never know what that is like from the inside.
- Reading time
- 4 min
- Difficulty
- Intermediate
- Branch
- Mind
- First posed
- Thomas Nagel, 'What Is It Like to Be a Bat?', The Philosophical Review, 1974
The setup
Bats navigate by echolocation. They emit high-pitched shrieks and perceive the world through the returning echoes, discriminating distance, size, shape, motion and texture in the dark. It is a sense as rich as sight, and completely unlike any sense we have.
In 1974 Thomas Nagel chose the bat to make a point. Bats are mammals, so most of us are confident they have experiences: there is something it is like to be a bat. But what is it like? You can imagine having webbed arms, flying at dusk, catching insects in your mouth and hanging upside down. Yet that only tells you what it would be like for you to behave like a bat. It does not tell you what it is like for a bat to be a bat.
Nagel's claim was that the bat's experience has a subjective character that is accessible only from a particular point of view, the bat's. No amount of objective, third-person information about its neurophysiology would capture it. And if that is true for bats, it is true for consciousness generally: physical science, which aims at a 'view from nowhere', leaves out the view from somewhere.
Why it matters
This short essay is one of the most cited papers in the philosophy of mind. Its phrase 'there is something it is like' became the standard definition of consciousness.
It also has practical implications for how we think about animal experience, and about whether we could ever understand the inner life of minds very different from our own, including artificial ones.
Key terms
- Phenomenal consciousnessThe felt, subjective aspect of experience: what it is like to see red, feel pain or taste coffee.
- SubjectivityThe first-person point of view: the way the world is given to a particular subject. Kierkegaard held that some truths can only be grasped in it.
- QualiaThe qualities of conscious experiences as they feel from the inside, such as the redness of red or the painfulness of pain. Singular: quale.
- PhysicalismThe view that everything that exists is physical, or is fixed by the physical facts.
- Explanatory gapJoseph Levine's term for the apparent impossibility of explaining why a given physical process should feel like anything at all from the inside.
The positions
Subjectivity resists physical explanation
Facts about what an experience is like are accessible only from a point of view. Objective science, by its nature, cannot capture them.
We can learn a great deal
There is nothing in principle unreachable about the bat's experience. Science can tell us much about what it is like, even if not by giving us the experience.
Knowing-how, not knowing-that
What we lack is not knowledge of some fact, but an ability: the ability to imagine or recognise the experience. That ability is not a gap in physical knowledge.
Arguments and objections
Subjectivity resists physical explanation
- Best argument
- Every advance of physical science moves toward a more objective description, one less dependent on any particular viewpoint. That is its strength. But experience is essentially tied to a point of view. So the more objective our description, the further it moves from experience. A Martian scientist could learn every physical fact about rainbows without knowing what they look like to us.
- Strongest objection
- That a fact is learned from a point of view does not mean it is a non-physical fact. You learn your location by looking around, but your location is still physical.
- The reply
- Nagel did not say physicalism is false, only that we do not currently understand how it could be true: we have, he wrote, no idea yet what a physical explanation of a mental phenomenon would even look like.
We can learn a great deal
- Best argument
- Daniel Dennett argued that we can work out a great deal about bat experience by studying what bats can discriminate, what they attend to and how they respond. We would learn, for instance, that bats can tell an insect from a falling leaf by its echo. Whatever is left over after all such facts are known is not a further fact at all.
- Strongest objection
- Knowing what a bat can discriminate is not the same as knowing what the discrimination feels like. This is just the gap Nagel described.
Knowing-how, not knowing-that
- Best argument
- David Lewis and Laurence Nemirow argued that knowing what an experience is like is a matter of having certain abilities, to imagine, remember and recognise it. Being unable to have bat experiences means lacking an ability, as one may lack the ability to ride a bicycle, not lacking information about the world.
- Strongest objection
- It seems one can learn a new fact when having an experience for the first time, not merely gain an ability. See Mary's room for the case that tests this.
Who argued what
- Subjectivity resists physical explanation Thomas Nagel, David Chalmers
- We can learn a great deal Daniel Dennett, Kathleen Akins
- Knowing-how, not knowing-that David Lewis, Laurence Nemirow
Variations
Blind echolocators
Some blind people, like Daniel Kish, have taught themselves to echolocate by making tongue clicks, and navigate on bicycles and hiking trails. Brain imaging shows they use visual cortex to process the echoes. Do they know what it is like to be a bat? A little? Or what it is like to be a human echolocator, which is something else again?
Other humans
If we cannot know what it is like to be a bat, can we know what it is like to be another person? Nagel noted that people blind from birth face a similar gap in understanding sight. Perhaps the problem begins long before bats.
Go deeper
Why a bat?
Nagel chose bats carefully. He wanted a creature close enough to us that we would be confident it had experiences (not a wasp, about which many have doubts), but with a sense different enough that we could not simply imagine its experience by analogy with ours. Bats, as mammals with a radically different dominant sense, were ideal.
Related ideas
Further reading and sources
- EncyclopediaStanford Encyclopedia of Philosophy: Qualia
- WikipediaWhat Is It Like to Be a Bat?
- BookMortal Questions, Thomas Nagel · contains the bat essay
- BookThe View from Nowhere, Thomas Nagel
- BookAn Immense World, Ed Yong
Open questions
- Is there a fact about what it is like to be a bat that no science could ever state?
- Can you know what it is like to be anyone other than yourself?
- If an alien had a sense we lack entirely, could we ever understand its world?