The Subjective Character of Experience


what is it like to be a bat? (1974)

By thomas nagel


in: Heil, pp. 528-38


I.  Introduction (528)

A.  Consciousness makes the mind-body problem especially difficult

B. this is perhaps why materialists like Smart (n. 1) do not give the problem sufficient attention

C. Materialists have focused on the problem of the reduction of mental to physical concepts, treating it like:

1. water and H2O

2. temperature and motion of molecules, etc.

D. Nagel will try to explain why these kinds of examples do not help us understand the relationship between mind and body

II. Consciousness (529)

A. Nagel believes that conscious experience exists in many different forms of animal life

1. although he is not sure that it exists in lower animals

2. or what would count as evidence for consciousness (529)

B. nevertheless, the fact that an organism has conscious experience at all, for Nagel, means that there is something that it is like to be that organism -- that is, something it is like for the organism

C. This "what it is like" he calls this the "subjective character" of experience

D. this subjective character of experience is not captured by any of the theories that try to reduce the mental to something else

1. these are all logically compatible with its absence

2. it can't be analyzed in terms of: 

a. functional or intentional states, since these can be ascribed to robots that behave like us but do not experience anything

b. causal role of experience in generating typical behavior, for similar reasons

3. this is not to deny that conscious mental states cause behavior, or can be characterized in functional terms

4. it is only to deny that these kinds of analyses of mental states would be complete

a. to reduce mental states to something else, one must begin by analyzing completely what is to be reduced

b.  if one leaves out the subjective character of mental states in this analysis, it is useless to proceed further (529, q.v.)

c.  no reason to think that a reduction that seems plausible when consciousness is left out can be extended to include consciousness (q.v.)

E. it is this subjective character of experience that is the most difficult thing for a physicalist theory to explain

1.  it's not possible to exclude the "phenomenological" features of experience from a reduction the way we exclude the phenomenal features of a substance when we give a physical or chemical account of it (529-30)

a.  in other words, we can't say that's just the way it looks to the human mind, for in this case, that is the very thing that we are trying to explain (530, q.v.)

b.  but it is impossible to give a physical explanation of this subjective character of an experience, since this is tied to a single or specific point of view, and that is precisely what an objective account of it would leave out (q.v.)

2. to explain the difference between the subjective (pour soi) and the objective (en soi), to illustrate the connection between subjectivity and point of view, and to show the importance of the subjective, he will turn to an example (530)

III. Bats

A.  assumes that bats, being mammals, have experience

B.  this means that there is something that it is like to be a bat

C.  however, their activities and sensory system are very different from ours

1. perceive distance, size, shape, motion, and texture of things through sonar, or echolocation

2.  thus there is no reason to believe their experience is subjectively like ours

D.  since our imagination draws on our own experience, it would not help just to imagine what it would be like to fly around at night listening to echoes, catching bugs in our mouths, etc. (530-31)

1. this would be only to imagine what it would be like for us to be bats (531)

2. what we want to know is what it would be like for a bat to be a bat

E. as long as our “fundamental structure” remains the same, our experiences would not be like those of a bat

1. it is not clear that we can attach any meaning to the suggestion that we could have the neurophysiological structure of a bat (531, q.v.)

2. even if we can imagine gradually being transformed into a bat, there is nothing in our present constitution that would allow us to imagine what that would be like

F. although we can ascribe various general types of experience to bats, such as hunger, fear, pain, and lust, we cannot know what the subjective character of each of these experiences is like

1. if there were conscious aliens, we may not even be able to characterize their experiences in these general terms

2. (note 6) by what it is "like," Nagel does not mean what it resembles, but how it is for the subject him or herself

3. this problem is not limited to bats and aliens, but exists even between one human being and another

a. for example, it is difficult to know what it is like to have been deaf and blind from birth

b. and this person has difficulties knowing what it is like to be us

c. but that does not prevent us from thinking that there is something that it is like to be that other person (531)

G. in the same way, bats and aliens would have difficulty in knowing what it is like to be a human being

1. it would be a mistake for the alien to conclude that since he can not imagine what it would be like to be us, we do not have conscious experience (532)

2. in the same way, it would also be a mistake for us to conclude that since we cannot imagine what it would be like to be a bat, the bat has no conscious experience

IV. The Relation between Facts and Conceptual Schemes

A. Nagel's belief in the reality of others' subjective experience implies a belief in the existence of facts beyond the reach of human concepts

1. this is not merely to assert the existence of facts for which we will never have the concepts to understand, because, say, we will all get wiped out by a nuclear war or an epidemic

2.  it is also to say that there are facts that we could never have the concepts to understand, even if humanity lasted forever, just because we are not made that way

3.  Nagel's reflection on what it is like to be a bat thus leads him to the conclusion that there are facts that do not consist in the truth of a proposition that can be expressed in a human language (532, q.v.)

4.  That is, he seems to mean “fact” in the sense of something that actually exists

B. although he does not want to pursue this topic here, he does think it allows him to say that facts about the subjective character of experience may be tied to a particular point of view

1. when he is talking about a particular point of view here, he is not talking here about the privacy of individual experience (533)

2. rather, he is talking about a type of or species point of view

a. there is a sense in which an individual human being can say that he or she knows what the experience of another, similar, human being is like

b. this task becomes more difficult as the creature is more different from us

5.  (note 8) Nagel is not raising simply the epistemological problem that we cannot know what it is like to be a bat, but the deeper problem that we cannot even form a concept of what it is like to be a bat in the first place  – and thus with even greater reason to know what it would be like (533, n. 8, q.v., cf. V.G.2 below)

V.  The Mind-Body Problem (533)

A. if facts about the subjective character of experience can be known only from a particular point of view, then it is a “mystery” how they could be observed in the physical operation of the organism

B. physical facts about the organism on the other hand are objective

1.  that is, they can be understood from many points of view by different sorts of organisms (533)

2.  one does not have to be a bat to understand bat neurophysiology or a human to understand human neurophysiology

C. this difference between the subjective and objective point of view is not alone an argument against reduction or the mind-body identity theory (indeed, it would be an instance of the intentional fallacy)

1. we can imagine an alien who does not have our visual system nevertheless being able to give an "objective" account of the rainbow, or lightning, or clouds

2. although the concepts of these things may be tied to a human point of view, the physical events picked out by them are not (533-34)

3. Nagel regards objective and subjective as a matter of degree (534)

a. (he is non-committal on the question whether there is an end-point on the continuum, a perfectly objective intrinsic nature of the thing)

b. and argues that in the case of something like the study of lightning, it makes sense to try to go as far as possible in the objective direction

D. in the case of experience, however, the connection to a particular point of view is much tighter

1. it is not clear what one could mean by the  "objective" character of experience, apart from the point of view of the subject of that experience

2. for instance, what would remain of what it is like to be a bat after one removed the bat’s point of view?

3. but if experience did not have, in addition to its subjective character, some objective nature that could be studied from different points of view, then how could we say that a Martian or even a human neurophysiologist was studying my mental processes, only from a different point of view, as he might study, say, lightning from a different point of view? 

4. (In other words, I think Nagel is trying to say, these experiences must have some objective existence.)

E. this raises a problem for mind-brain reduction

1. in successful types of reduction, we move in a direction toward greater objectivity and away from a specifically human point of view (534)

a. e.g., sound = waves in a medium (535)

b. blue = short wave lengths of light

c. members of different species here could refer to a common reality only by leaving their species point-of-view behind

2. however, it does not seem that we can follow this model with experience

a. here it seems to make no sense to talk about moving from subjective appearance to objective reality

b. it does not seem that we can get to the underlying reality by leaving the human point of view behind and characterizing our experience in such a way that even aliens could understand

c.  in fact, this would take us further from, rather than closer to, the real nature of human experience

F. Nagel is critical of recent philosophy that tries to substitute an objective or behavioral account of mind for the "real thing" so that there will be nothing left over that cannot be reduced (535 q.v.)

1. If we believe that a physical theory of the mind should explain the subjective character of experience, we have to admit that no such theory does this (535)

2. If it is true that mental processes are physical brain processes, it is nevertheless true that there is something that it is like to undergo such brain processes

3. What it is for this to be true remains a mystery

G. however, Nagel does not wish to conclude that physicalism is false (536)

1. if a physicalist hypothesis begins with a faulty analysis of mind, we cannot conclude anything

2. What we should say is that physicalism is a position we cannot even understand because we have no idea what it would be like for it to be true

H. Objection: the physicalist claim that "mental states are brain states" is not meaningless

1. in order to understand it, it is not necessary to know which brain states they are

2. all we need to know is the meaning of "is" or "are," and what could be simpler?

I. Reply:

1. the apparent clarity of "is" is deceptive

2. our understanding of sentences like "X is Y" depends on our knowledge of X and Y and what they refer to, and not on the meaning of the word "is" (536)

3. when X and Y are very different things, we typically do not understand such sentences

a.  for example, when someone who does not understand physics is told that "Matter is energy"

b.  knowing what "is" means doesn't help (536-37)

4. our present understanding of the claim that "mental states are brain states" is similar to that of the ancient Greeks trying to understand "matter is energy" (537)

a. we require more than the meaning of "is"

b. we don't know how a mental and a physical term could refer to the same thing.  if we pretend that they can, we end up either:

1.) referring not to the physical states themselves but to the subjective mental states by which we know them (537, q.v.)

2.) or, with a false account of how mental states refer, e.g., a behaviorist account

J. Nevertheless, Nagel points out, we may have evidence for something that we do not understand

1. e.g., the person ignorant of insect metamorphosis who locks the caterpillar away in a safe and takes out a butterfly weeks later has evidence that the caterpillar turned into a butterfly (537)

2. it is possible that this is the position we are in with respect to the mind-body identity theory: 

a. we have evidence that sensations are physical processes, although we don't really understand how

b. Davidson argues that if mental events have physical causes and effects, they must have physical descriptions (q.v.)

VI. A proposal

A. As Nagel sees it, there has been very little work done on the question of whether any sense can be made of experiences having an objective character

1. that is, does it make sense to talk about what our experiences are really like, as opposed to how they appear to us?

2. we cannot address the problem of giving a physical account of the nature of mental states unless we can first understand how they can have an objective nature

3. this question is also closely connected to that of the existence of other minds (537 n.14)

B. So Nagel makes a proposal:  (538)

1. to put aside temporarily the question of the relationship between the mind and brain

2.  to try to achieve a more objective understanding of the mental in its own right (538)

C. to do this, we need new concepts and a new method:  an "objective phenomenology" not dependent on taking the point of view of the subject of experience

1. the goal would be to describe the subjective character of experience in a way that could be understood by those not capable of such experience

2.  we need such a method to describe the experience of bats

3.  but we could also begin with humans, for example, by trying to figure out how to explain to someone blind from birth what it is like to see

4.  although Nagel concedes that we would eventually reach "a blank wall," he nevertheless thinks we could do a better job of this than we can at present, perhaps by giving objective descriptions of structural features of perception

D. An objective phenomenology of this sort, Nagel thinks, would allow questions about the physical basis of experience to make more sense