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What is it like to be a bat?

Thomas Nagel

[From The Philosophical Review LXXXIII, 4 (October 1974):

435-50.]

Consciousness is what makes the mind-body problem r eally intractable. Perhaps that is why current

discussions of the problem give it little attention or get it obviously wrong. The recent wave of

reductionist euphoria has produced several analyses of mental phenomena and mental concepts designed

to explain the possibility of some variety of mater ialism, psychophysical identification, or reduction .

1 But

the problems dealt with are those common to this ty pe of reduction and other types, and what makes the

mind-body problem unique, and unlike the water-H

2O problem or the Turing machine-IBM machine

problem or the lightning-electrical discharge probl em or the gene-DNA problem or the oak

tree-hydrocarbon problem, is ignored.

Every reductionist has his favorite analogy from mo dern science. It is most unlikely that any of these

unrelated examples of successful reduction will she d light on the relation of mind to brain. But

philosophers share the general human weakness for e xplanations of what is incomprehensible in terms

suited for what is familiar and well understood, th ough entirely different. This has led to the acceptance of

implausible accounts of the mental largely because they would permit familiar kinds of reduction. I shall

try to explain why the usual examples do not help u s to understand the relation between mind and

body—why, indeed, we have at present no conception of what an explanation of the physical nature of a

mental phenomenon would be. Without consciousness t he mind-body problem would be much less

interesting. With consciousness it seems hopeless. The most important and characteristic feature of

conscious mental phenomena is very poorly understoo d. Most reductionist theories do not even try to

explain it. And careful examination will show that no currently available concept of reduction is

applicable to it. Perhaps a new theoretical form ca n be devised for the purpose, but such a solution, if it

exists, lies in the distant intellectual future.

Conscious experience is a widespread phenomenon. It occurs at many levels of animal life, though we

cannot be sure of its presence in the simpler organ isms, and it is very difficult to say in general what

provides evidence of it. (Some extremists have been prepared to deny it even of mammals other than

man.) No doubt it occurs in countless forms totally unimaginable to us, on other planets in other solar

systems throughout the universe. But no matter how the form may vary, the fact that an organism has

conscious experience at all means, basically, that there is something it is li ke to be that organism. There

may be further implications about the form of the e xperience; there may even (though I doubt it) be

implications about the behavior of the organism. Bu t fundamentally an organism has conscious mental

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

organism.

We may call this the subjective character of experi ence. It is not captured by any of the familiar, recently

devised reductive analyses of the mental, for all o f them are logically compatible with its absence. I t is not

analyzable in terms of any explanatory system of fu nctional states, or intentional states, since these could What is it like to be a bathttp://members.aol.com/NeoNoetics/Nagel_Bat.html

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be ascribed to robots or automata that behaved like people though they experienced nothing. 2 It is not

analyzable in terms of the causal role of experienc es in relation to typical human behavior—for simila r

reasons.

3 I do not deny that conscious mental states and eve nts cause behavior, nor that they may be given

functional characterizations. I deny only that this kind of thing exhausts their analysis. Any reducti onist

program has to be based on an analysis of what is t o be reduced. If the analysis leaves something out, the

problem will be falsely posed. It is useless to bas e the defense of materialism on any analysis of men tal

phenomena that fails to deal explicitly with their subjective character. For there is no reason to sup pose

that a reduction which seems plausible when no atte mpt is made to account for consciousness can be

extended to include consciousness. With out some id ea, therefore, of what the subjective character of

experience is, we cannot know what is required of p hysicalist theory.

While an account of the physical basis of mind must explain many things, this appears to be the most

difficult. It is impossible to exclude the phenomen ological features of experience from a reduction in the

same way that one excludes the phenomenal features of an ordinary substance from a physical or chemical

reduction of it—namely, by explaining them as effec ts on the minds of human observers.

4 If physicalism

is to be defended, the phenomenological features mu st themselves be given a physical account. But when

we examine their subjective character it seems that such a result is impossible. The reason is that every

subjective phenomenon is essentially connected with a single point of view, and it seems inevitable that

an objective, physical theory will abandon that poi nt of view.

Let me first try to state the issue somewhat more f ully than by referring to the relation between the

subjective and the objective, or between the pour-soi and the en-soi. This is far from easy. Facts about

what it is like to be an X are very peculiar, so peculiar that some may be in clined to doubt their reality, or

the significance of claims about them. To illustrat e the connection between subjectivity and a point o f

view, and to make evident the importance of subject ive features, it will help to explore the matter in

relation to an example that brings out clearly the divergence between the two types of conception,

subjective and objective.

I assume we all believe that bats have experience. After all, they are mammals, and there is no more d oubt

that they have experience than that mice or pigeons or whales have experience. I have chosen bats instead

of wasps or flounders because if one travels too fa r down the phylogenetic tree, people gradually shed

their faith that there is experience there at all. Bats, although more closely related to us than thos e other

species, nevertheless present a range of activity a nd a sensory apparatus so different from ours that the

problem I want to pose is exceptionally vivid (thou gh it certainly could be raised with other species). Even

without the benefit of philosophical reflection, an yone who has spent some time in an enclosed space w ith

an excited bat knows what it is to encounter a fund amentally alien form of life.

I have said that the essence of the belief that bat s have experience is that there is something that i t is like

to be a bat. Now we know that most bats (the microc hiroptera, to be precise) perceive the external world

primarily by sonar, or echolocation, detecting the reflections, from objects within range, of their own

rapid, subtly modulated, high-frequency shrieks. Th eir brains are designed to correlate the outgoing

impulses with the subsequent echoes, and the inform ation thus acquired enables bats to make precise

discriminations of distance, size, shape, motion, a nd texture comparable to those we make by vision. B ut

bat sonar, though clearly a form of perception, is not similar in its operation to any sense that we possess,

and there is no reason to suppose that it is subjec tively like anything we can experience or imagine. This

appears to create difficulties for the notion of wh at it is like to be a bat. We must consider whether any

method will permit us to extrapolate to the inner l ife of the bat from our own case,

5 and if not, what

alternative methods there may be for understanding the notion.

Our own experience provides the basic material for our imagination, whose range is therefore limited. It

will not help to try to imagine that one has webbin g 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-fre quency sound signals; and that one spends the day What is it like to be a bathttp://members.aol.com/NeoNoetics/Nagel_Bat.html

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hanging upside down by one’s feet in an attic. In so far as I can imagine this (which is not very far), it tells

me only what it would be like for me to behave as a bat behaves. But that is not the qu estion. I want to

know what it is like for a bat to be a bat. Yet if I try to imagine this, I am re stricted to the resources of my

own mind, and those resources are inadequate to the task. I cannot perform it either by imagining

additions to my present experience, or by imagining segments gradually subtracted from it, or by

imagining some combination of additions, subtractio ns, and modifications.

To the extent that I could look and behave like a w asp or a bat without changing my fundamental

structure, my experiences would not be anything lik e the experiences of those animals. On the other hand,

it is doubtful that any meaning can be attached to the supposition that I should possess the internal

neurophysiological constitution of a bat. Even if I could by gradual degrees be transformed into a bat ,

nothing in my present constitution enables me to im agine what the experiences of such a future stage of

myself thus metamorphosed would be like. The best e vidence would come from the experiences of bats, if

we only knew what they were like.

So if extrapolation from our own case is involved i n the idea of what it is like to be a bat, the

extrapolation must be incompletable. We cannot form more than a schematic conception of what it is like.

For example, we may ascribe general types of experience on the basis of the animal’s structu re and

behavior. Thus we describe bat sonar as a form of t hree-dimensional forward perception; we believe tha t

bats feel some versions of pain, fear, hunger, and lust, and that they have other, more familiar types of

perception besides sonar. But we believe that these experiences also have in each case a specific

subjective character, which it is beyond our abilit y to conceive. And if there’s conscious life elsewh ere in

the universe, it is likely that some of it will not be describable even in the most general experienti al terms

available to us.

6 (The problem is not confined to exotic cases, howe ver, for it exists between one person

and another. The subjective character of the experi ence of a person deaf and blind from birth is not

accessible to me, for example, nor presumably is mi ne to him. This does not prevent us each from

believing that the other’s experience has such a su bjective character.)

If anyone is inclined to deny that we can believe i n the existence of facts like this whose exact nature we

cannot possibly conceive, he should reflect that in contemplating the bats we are in much the same

position that intelligent bats or Martians

7 would occupy if they tried to form a conception of what it was

like to be us. The structure of their own minds mig ht make it impossible for them to succeed, but we

know they would be wrong to conclude that there is not anything precise that it is like to be us: that only

certain general types of mental state could be ascr ibed to us (perhaps perception and appetite would b e

concepts common to us both; perhaps not). We know t hey would be wrong to draw such a skeptical

conclusion because we know what it is like to be us . And we know that while it includes an enormous

amount of variation and complexity, and while we do not possess the vocabulary to describe it adequately,

its subjective character is highly specific, and in some respects describable in terms that can be und erstood

only by creatures like us. The fact that we cannot expect ever to accommodate in our language a detail ed

description of Martian or bat phenomenology should not lead us to dismiss as meaningless the claim that

bats and Martians have experiences fully comparable in richness of detail to our own. It would be fine if

someone were to develop concepts and a theory that enabled us to think about those things; but such an

understanding may be permanently denied to us by th e limits of our nature. And to deny the reality or

logical significance of what we can never describe or understand is the crudest form of cognitive

dissonance.

This brings us to the edge of a topic that requires much more discussion than I can give it here: name ly,

the relation between facts on the one hand and conc eptual schemes or systems of representation on the

other. My realism about the subjective domain in al l its forms implies a belief in the existence of facts

beyond the reach of human concepts. Certainly it is possible for a human being to believe that there are

facts which humans never will possess the requisite concepts to represent or comp rehend. Indeed, it would

be foolish to doubt this, given the finiteness of h umanity’s expectations. After all there would have been

transfinite numbers even if everyone had been wiped out by the Black Death before Cantor discovered

them. But one might also believe that there are fac ts which could not ever be represented or What is it like to be a bathttp://members.aol.com/NeoNoetics/Nagel_Bat.html

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comprehended by human beings, even if the species lasted for ever—simply because our structure does

not permit us to operate with concepts of the requi site type. This impossibility might even be observe d by

other beings, but it is not clear that the existenc e of such beings, or the possibility of their exist ence, is a

precondition of the significance of the hypothesis that there are humanly inaccessible facts. (After all, the

nature of beings with access to humanly inaccessibl e facts is presumably itself a humanly inaccessible

fact.) Reflection on what it is like to be a bat se ems to lead us, therefore, to the conclusion that t here are

facts that do not consist in the truth of propositi ons expressible in a human language. We can be

compelled to recognize the existence of such facts without being able to state or comprehend them.

I shall not pursue this subject, however. Its beari ng on the topic before us (namely, the mind-body

problem) is that it enables us to make a general ob servation about the subjective character of experience.

Whatever may be the status of facts about what it i s like to be a human being, or a bat, or a Martian, these

appear to be facts that embody a particular point o f view.

I am not adverting here to the alleged privacy of e xperience to its possessor. The point of view in qu estion

is not one accessible only to a single individual. Rather it is a type. It is often possible to take up a point of

view other than one’s own, so the comprehension of such facts is not limited to one’s own case. There is a

sense in which phenomenological facts are perfectly objective: one person can know or say of another

what the quality of the other’s experience is. They are subjective, however, in the sense that even this

objective ascription of experience is possible only for someone sufficiently similar to the object of

ascription to be able to adopt his point of view—to understand the ascription in the first person as well as

in the third, so to speak. The more different from oneself the other experiencer is, the less success one can

expect with this enterprise. In our own case we occ upy the relevant point of view, but we will have as

much difficulty understanding our own experience pr operly if we approach it from another point of view

as we would if we tried to understand the experienc e of another species without taking up its point of

view.

8

This bears directly on the mind-body problem. For i f 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 facts par excellence—the kind that can be observed and understood from many points

of view and by individuals with differing perceptua l systems. There are no comparable imaginative

obstacles to the acquisition of knowledge about bat neurophysiology by human scientists, and intellige nt

bats or Martians might learn more about the human b rain than we ever will.

This is not by itself an argument against reduction . A Martian scientist with no understanding of visu al

perception could understand the rainbow, or lightni ng, or clouds as physical phenomena, though he woul d

never be able to understand the human concepts of r ainbow, lightning, or cloud, or the place these things

occupy in our phenomenal world. The objective natur e of the things picked out by these concepts could be

apprehended by him because, although the concepts t hemselves are connected with a particular point of

view and a particular visual phenomenology, the thi ngs apprehended from that point of view are not: they

are observable-from the point of view but external to it; hence they can be comprehended from other

points of view also, either by the same organisms o r by others. Lightning has an objective character that is

not exhausted by its visual appearance, and this ca n be investigated by a Martian without vision. To b e

precise, it has a more objective character than is revealed in its visual appearance. In speaking of the move

from subjective to objective characterization, I wi sh to remain noncommittal about the existence of an end

point, the completely objective intrinsic nature of the thing, which one might or might not be able to

reach. It may be more accurate to think of objectiv ity as a direction in which the understanding can travel.

And in understanding a phenomenon like lightning, i t is legitimate to go as far away as one can from a

strictly human viewpoint.

9

In the case of experience, on the other hand, the c onnection with a particular point of view seems muc h

closer. It is difficult to understand what could be meant by the objective character of an experience, apart

from the particular point of view from which its su bject apprehends it. After all, what would be left of What is it like to be a bathttp://members.aol.com/NeoNoetics/Nagel_Bat.html

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what it was like to be a bat if one removed the viewpoint of the bat? But if experience does not have, in

addition to its subjective character, an objective nature that can be apprehended from many different

points of view, then how can it be supposed that a Martian investigating my brain might be observing

physical processes which were my mental processes ( as he might observe physical processes which were

bolts of lightning), only from a different point of view? How, for that matter, could a human physiolo gist

observe them from another point of view?

10

We appear to be faced with a general difficulty abo ut psychophysical reduction. In other areas the process

of reduction is a move in the direction of greater objectivity, toward a more, accurate view of the re al

nature of things. This is accomplished by reducing our dependence on individual or species-specific po ints

of view toward the object of investigation. We desc ribe it not in terms of the impressions it makes on our

senses, but in terms of its more general effects an d of properties detectable by means other than the human

senses. The less it depends on a specifically human viewpoint, the more objective is our description. It is

possible to follow this path because although the c oncepts and ideas we employ in thinking about the

external world are initially applied from a point o f view that involves our perceptual apparatus, they are

used by us to refer to things beyond themselves—tow ard which we have the phenomenal point of view.

Therefore we can abandon it in favor of another, an d still be thinking about the same things.

Experience itself however, does not seem to fit the pattern. The idea of moving from appearance to rea lity

seems to make no sense here. What is the analogue i n this case to pursuing a more objective

understanding of the same phenomena by abandoning t he initial subjective viewpoint toward them in

favour of another that is more objective but concer ns the same thing? Certainly it appears unlikely that we

will get closer to the real nature of human experie nce by leaving behind the particularity of our huma n

point of view and striving for a description in ter ms accessible to beings that could not imagine what it

was like to be us. If the subjective character of e xperience is fully comprehensible only from one poi nt 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.

In a sense, the seeds of this objection to the redu cibility of experience are already detectable in su ccessful

cases of reduction; for in discovering sound to be, in reality, a wave phenomenon in air or other medi a, we

leave behind one viewpoint to take up another, and the auditory, human or animal viewpoint that we lea ve

behind remains unreduced. Members of radically diff erent species may both understand the same physical

events in objective terms, and this does not requir e that they understand the phenomenal forms in whic h

those events appear to the senses of members of the other species. Thus it is a condition of their referring

to a common reality that their more particular view points are not part of the common reality that they both

apprehend. The reduction can succeed only if the sp ecies-specific viewpoint is omitted from what is to be

reduced.

But while we are right to leave this point of view aside in seeking a fuller understanding of the exte rnal

world, we cannot ignore it permanently, since it is the essence of the internal world, and not merely a

point of view on it. Most of the neobehaviorism of recent philosophical psychology results from the effort

to substitute an objective concept of mind for the real thing, in order to have nothing left over which

cannot be reduced. If we acknowledge that a physica l theory of mind must account for the subjective

character of experience, we must admit that no pres ently available conception gives us a clue how this

could be done. The problem is unique. If mental pro cesses are indeed physical processes, then there is

something it is like, intrinsically,

11 to undergo certain physical processes. What it is for such a thing to be

the case remains a mystery.

What moral should be drawn from these reflections, and what should be done next? It would be a mistake

to conclude that physicalism must be false. Nothing is proved by the inadequacy of physicalist hypotheses

that assume a faulty objective analysis of mind. It would be truer to say that physicalism is a position we

cannot understand because we do not at present have any conception of how it might be true. Perhaps it

will be thought unreasonable to require such a conc eption as a condition of understanding. After all, it

might be said, the meaning of physicalism is clear enough: mental states are states of the body; menta l What is it like to be a bathttp://members.aol.com/NeoNoetics/Nagel_Bat.html

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events are physical events. We do not know which physical states and events they are, but that shoul d not

prevent us from understanding the hypothesis. What could be clearer than the words ‘is’ and ‘are’?

But I believe it is precisely this apparent clarity of the word ‘is’ that is deceptive. Usually, when we are

told that X is Y we know how it is supposed to be true, but that depends on a c onceptual or theoretical

background and is not conveyed by the ‘is’ alone. W e know how both “X” and ” Y ” refer, and the kinds of

things to which they refer, and we have a rough ide a how the two referential paths might converge on a

single thing, be it an object, a person, a process, an event or whatever. But when the two terms of th e

identification are very disparate it may not be so clear how it could be true. We may not have even a rough

idea of how the two referential paths could converg e, or what kind of things they might converge on, and

a theoretical framework may have to be supplied to enable us to understand this. Without the framework ,

an air of mysticism surrounds the identification.

This explains the magical flavor of popular present ations of fundamental scientific discoveries, given out

as propositions to which one must subscribe without really understanding them. For example, people are

now told at an early age that all matter is really energy. But despite the fact that -‘they know what ‘is’

means, most of them never form a conception of what makes this claim true, because they lack the

theoretical background.

At the present time the status of physicalism is si milar to that which the hypothesis that matter is e nergy

would have had if uttered by a pre-Socratic philoso pher. We do not have the beginnings of a conception of

how it might be true. In order to understand the hy pothesis that a mental event is a physical event, we

require more than an understanding of the word ‘is’ . The idea of how a mental and a physical term migh t

refer to the same thing is lacking, and the usual a nalogies with theoretical identification in other fields fail

to supply it. They fail because if we construe the reference of mental terms to physical events on the usual

model, we either get a reappearance of separate sub jective events as the effects through which mental

reference to physical events is secured, or else we get a false account of how mental terms refer (for

example, a causal behaviorist one).

Strangely enough, we may have evidence for the trut h of something we cannot really understand. Suppose

a caterpillar is locked in a sterile safe by someon e unfamiliar with insect metamorphosis, and weeks l ater

the safe is reopened, revealing a butterfly. If the person knows that the safe has been shut the whole time,

he has reason to believe that the butterfly is or w as once the caterpillar, without having any idea in what

sense this might be so. (One possibility is that th e caterpillar contained a tiny winged parasite that

devoured it and grew into the butterfly.)

It is conceivable that we are in such a position wi th regard to physicalism. Donald Davidson has argue d

that if mental events have physical causes and effe cts, they must have physical descriptions. He holds that

we have reason to believe this even though we do no t—and in fact could not—have a general

psychophysical theory.

12 His argument applies to intentional mental events, but I think we also have some

reason to believe that sensations are physical proc esses, without being in a position to understand ho w.

Davidson’s position is that certain physical events have irreducibly mental properties, and perhaps so me

view describable in this way is correct. But nothin g of which we can now form a conception corresponds

to it; nor have we any idea what a theory would be like that enabled us to conceive of it.

13

Very little work has been done on the basic questio n (from which mention of the brain can be entirely

omitted) whether any sense can be made of experienc es’ having an objective character at all. Does it make

sense, in other words, to ask what my experiences a re really like, as opposed to how they appear to me?

We cannot genuinely understand the hypothesis that their nature is captured in a physical description

unless we understand the more fundamental idea that they have an objective nature (or that objective

processes can have a subjective nature).

14

I should like to close with a speculative proposal. It may be possible to approach the gap between

subjective and objective from another direction. Se tting aside temporarily the relation between the mind What is it like to be a bathttp://members.aol.com/NeoNoetics/Nagel_Bat.html

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and the brain, we can pursue a more objective understanding of the mental in its own right. At present we

are completely unequipped to think about the subjec tive character of experience without relying on the

imagination—without taking up the point of view of the experiential subject. This should be regarded as a

challenge to form new concepts and devise a new met hod—an objective phenomenology not dependent

on empathy or the imagination. Though presumably it would not capture everything, its goal would be to

describe, at least in part, the subjective characte r of experiences in a form comprehensible to beings

incapable of having those experiences.

We would have to develop such a phenomenology to de scribe the sonar experiences of bats; but it would

also be possible to begin with humans. One might tr y, for example, to develop concepts that could be used

to explain to a person blind from birth what it was like to see. One would reach a blank wall eventual ly,

but it should be possible to devise a method of exp ressing in objective terms much more than we can at

present, and with much greater precision. The loose intermodal analogies—for example, ‘Red is like the

sound of a trumpet’—which crop up in discussions of this subject are of little use. That should be clear to

anyone who has both heard a trumpet and seen red. B ut structural features of perception might be more

accessible to objective description, even though so mething would be left out. And concepts alternative to

those we learn in the first person may enable us to arrive at a kind of understanding even of our own

experience which is denied us by the very ease of d escription and lack of distance that subjective concepts

afford.

Apart from its own interest, a phenomenology that i s in this sense objective may permit questions about

the physically basis of experience to assume a more intelligible form. Aspects of subjective experience

that admitted this kind of objective description mi ght be better candidates for objective explanations of a

more familiar sort. But whether or not this guess i s correct, it seems unlikely that any physical theory of

mind can be contemplated until more thought has bee n given to the general problem of subjective and

objective. Otherwise we cannot even pose the mind-b ody problem without sidestepping it.

NOTES:

1 Examples are J. J. C. Smart, Philosophy and Scientific Realism (London: Routledge & Kegan Paul, 1963); David K.

Lewis, ‘An Argument for the Identity Theory’, Journal of Philosophy, LXIII (1966), reprinted with addenda in David

M. Rosenthal, Materialism & the Mind-Body Problem , (Engelwood Cliffs, NJ.: Prentice-Hall, 1971); Hil ary Putnam,

‘Psychological Predicates’, in Art, Mind, & Religion, ed. W. H. Capitan and D. D. Merrill (Pittsburgh: University of

Pittsburgh Press, 1967), reprinted in Materialism, ed. Rosenthal, as ‘The Nature of Mental States’; D. M. Armstrong, A

Materialist Theory of the Mind (London: Routledge & Kegan Paul, 1968); D. C. Denn ett, Content and Consciousness

(London: Routledge & Kegan Paul, 1969). I have expr essed earlier doubts in ‘Armstrong on the Mind’, Philosophical

Review , LXXIX (1970), 394-403; a review of Dennett, Journal of Philosophy, LXIX (1972); and chapter 11 above.

See also Saul Kripke, ‘Naming and Necessity’. in Semantics of Natural Language, ed. D. Davidson and G. Harman

(Dordrecht: Reidel, 1972), esp. pp. 334-42; and M. T. Thornton, ‘Ostensive Terms and Materialism’, The Monist, LVI

(1972), 193-214.

2 Perhaps there could not actually be such robots. P erhaps anything complex enough to behave like a per son would

have experiences. But that, if true, is a fact whic h cannot be discovered merely by analyzing the conc ept of experience.

3 It is not equivalent to that about which we are incorrigible, both because we are not incorrigible ab out experience

and because experience is present in animals lackin g language and thought, who have no beliefs at all about their

experiences.

4 Cf. Richard Rorty, ‘Mind-Body Identity, Privacy, a nd Categories’, Review of Metaphysics , XIX (1965), esp. 37-8.

5 By ‘our own case’ I do not mean just ‘my own case’, but rather the mentalistic ideas that we apply unproblematically

to ourselves and other human beings.

6 Therefore the analogical form of the English expres sion ‘what it is like’ is misleading. It does not mean ‘what (in our

experience) it resembles’, but rather ‘how it is for the subject himself’. What is it like to be a bathttp://members.aol.com/NeoNoetics/Nagel_Bat.html

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7 Any intelligent extraterrestrial beings totally different from us.

8 It may be easier than I suppose to transcend inter -species barriers with the aid of the imagination. For example, blind

people are able to detect objects near them by a fo rm of sonar, using vocal clicks or taps of a cane. Perhaps if one

knew what that was like, one could by extension ima gine roughly what it was like to possess the much more refined

sonar of a bat. The distance between oneself and ot her persons and other species can fall anywhere on a continuum.

Even for other persons the understanding of what it is like to be them is only partial, and when one moves to species

very different from oneself, a lesser degree of par tial understanding may still be available. The imag ination is

remarkably flexible. My point, however, is not that we cannot know what it is like to be a bat. I am not raising that

epistemological problem. My point is rather that ev en to form a conception of what it is like to be a bat (and a fortiori

to know what it is like to be a bat) one must take up the bat’s point of view. If one can take it up roughly, or partially,

then one’s conception will also be rough or partial . Or so it seems in our present state of understanding.

9 The problem I am going to raise can therefore be p osed even if the distinction between more subjective and more

objective descriptions or viewpoints can itself be made only within a larger human point of view. I do not accept this

kind of conceptual relativism, but it need not be r efuted to make the point that psychophysical reduct ion cannot be

accommodated by the subjective-to-objective model f rom other cases.

10 The problem is not just that when I look at the Mona Lisa, my visual experience has a certain quality, no tr ace of

which is to be found by someone looking into my bra in. For even if he did observe there a tiny image of the Mona

Lisa , he would have no reason to identify it with the e xperience.

11 The relation would therefore not be a contingent o ne, like that of a cause and its distinct effect. It would be

necessarily true that a physical state felt a certa in way. Saul Kripke in Semantics of Natural Language , (ed. Davidson

and Harman) argues that causal behaviorist and rela ted analyses of the mental fail because they construe, e.g., ‘pain’ as

a merely contingent name of pains. The subjective c haracter of an experience (‘its immediate phenomeno local quality’

Kripke calls it (p. 340)) is the essential property left out by such analyses, and the one in virtue o f which it is,

necessarily , the experience it is. My view is closely related to his. Like Kripke, I find the hypothesis that a c ertain

brain state should necessarily have a certain subje ctive character incomprehensible without further ex planation. No

such explanation emerges from theories which view t he mind-brain relation as contingent, but perhaps there are other

alternatives, not yet discovered.

A theory that explained how the mind-brain relation was necessary would still leave us with Kripke’s problem of

explaining why it nevertheless appears contingent. That difficulty seems to me surmountable, in the fo llowing way.

We may imagine something by representing it to ours elves either perceptually, sympathetically, or symbolically. I shall

not try to say how symbolic imagination works, but part of what happens in the other two cases is this. To imagine

something perceptually, we put ourselves in a consc ious state resembling the state we would be in if we perceived it.

To imagine something sympathetically, we put oursel ves in a conscious state resembling the thing itself. (This method

can be used only to imagine mental events and stare s—our own or another’s.) When we try to imagine a m ental state

occurring without its associated brain state, we fi rst sympathetically imagine the occurrence of the m ental state: that is,

we put ourselves into a state that resembles it men tally. At the same time, we attempt perceptually to imagine the

nonoccurrence of the associated physical state, by putting ourselves into another state unconnected wi th the first; one

resembling that which we would be in if we perceive d the nonoccurrence of the physical state. Where the imagination

of physical features is perceptual and the imaginat ion of mental features is sympathetic, it appears to us that we can

imagine any experience occurring without its associ ated brain state, and vice versa. The relation between them will

appear contingent even if it is necessary, because of the independence of the disparate types of imagi nation.

(Solipsism incidentally, results if one misinterpre ts sympathetic imagination as if it worked like per ceptual

imagination: it then seems impossible to imagine an y experience that is not one’s own.)

12 See ‘Mental Events’ in Experience and Theory , ed. Lawrence Foster and J. W. Swanson (Amherst: U niversity of

Massachusetts Press, 1970); though I do not underst and the argument against psychophysical laws.

13 Similar remarks apply to my paper ‘Physicalism’, Philosophical Review, LXXIV (1965), 339-56, reprinted with

postscript in Modern Materialism , ed. John O’Connor (New York: Harcourt Brace Jovan ovich, 1969).

14 This question also lies at the heart of the problem of other minds, whose close connection with the m ind-body

problem is often overlooked. If one understood how subjective experience could have an objective nature, one would What is it like to be a bathttp://members.aol.com/NeoNoetics/Nagel_Bat.html

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understand the existence of subjects other than oneself.

15 I have not defined the term ‘physical’. Obviously it does not apply just to what can be described by the concepts of

contemporary physics, since we expect further devel opments. Some may think there is nothing to prevent mental

phenomena from eventually being recognized as physi cal in their own right. But whatever else may be said of the

physical, it has to be objective. So if our idea of the physical ever expands to include mental phenom ena, it will have

to assign them an objective character—whether or no t this is done by analyzing them in terms of other phenomena

already regarded as physical It seems to me more li kely, however, that mental-physical relations will eventually be

expressed in a theory whose fundamental terms canno t be placed clearly in either category.