Contribution
The paper gives the subjective character of experience the definition that is still standard: “an organism has conscious mental states if and only if there is something that it is like to be that organism”. It then argues that this feature is what makes the mind-body problem unlike every successful reduction the reductionists of the day cited: water/H₂O, lightning/electrical discharge, gene/DNA.
Key insight
Reduction in science works by abandoning a point of view. Take sound: we stop describing it by how it strikes the ear and describe it as a wave in a medium. We still refer to the same thing, and the auditory viewpoint we leave behind “remains unreduced”. Experience is the viewpoint itself, not something seen from it. So the move that makes other reductions succeed is exactly the one that loses the thing to be reduced.
Assumptions
- Bats have experience. This is taken as common ground (“I assume we all believe that bats have experience”). Bats are chosen because they are mammals, so the belief is secure, and because their sonar is unlike any human sense, so the problem is vivid.
- Imagination is bounded by one’s own experience. Adding to, subtracting from or modifying one’s own experience yields what it would be like for me to behave as a bat, not what it is like for a bat to be a bat.
- The physical is objective by definition (fn. 15). “Whatever else may be said of the physical, it has to be objective.” Nagel leaves “physical” otherwise undefined.
- The realist premise. There can be facts beyond the reach of human concepts. Nagel’s analogy: transfinite numbers would exist even if everyone had died before Cantor.
Key results
This is an argument, not an empirical paper. Its conclusions, in the order the paper reaches them:
- The subjective character of experience is not captured by any available reductive analysis, because each is logically compatible with its absence.
- Facts about what it is like to be an X embody a particular point of view. This is a type of viewpoint, not a private one. One person can know another’s experience to the extent that they can adopt it.
- Knowledge of bat neurophysiology faces no such obstacle. Intelligent bats or Martians might learn more about the human brain than we will.
- A physical theory of mind must therefore explain how a single thing can have a subjective character. No present conception says how, and no analogy from other reductions supplies one.
- Physicalism is not thereby false. We can even have evidence for it without understanding it: the caterpillar in the sealed safe that is found to be a butterfly. Nagel reads Davidson’s anomalous monism this way.
- The question that comes first, and that can be posed without mentioning the brain, is whether experiences can have an objective character at all.
Claims
| # | claim | strength | basis |
|---|---|---|---|
| C1 | Conscious ⇔ there is something it is like to be the organism | definitional | stipulated as what the belief that bats have experience amounts to |
| C2 | Functional, intentional and causal-role analyses omit subjective character | argued | each is compatible with robots that behave like people and experience nothing; fn. 2 concedes such robots may be impossible, but not by analysis |
| C3 | Subjective facts are tied to a type of point of view, not to an individual | argued | we ascribe experience across persons; understanding degrades with dissimilarity (fn. 8: a continuum, with human echolocation as a partial bridge) |
| C4 | The standard subjective-to-objective reduction pattern cannot apply to experience | argued | there is no appearance/reality gap in experience for objectivity to close |
| C5 | Physicalism is not refuted, but currently not understandable | argued | the ‘is’ of identity needs a framework showing how two referential paths converge, and none exists |
| C6 | An objective phenomenology is possible and worth building | speculative | proposal only; suggests starting with explaining sight to the congenitally blind, and structural features of perception |
Method
Conceptual argument through a worked example. The bat stands for any experiencer whose point of view is far from ours. The paper reasons from contrast cases: lightning, rainbows, and sound as seen by a Martian scientist. The fifteen footnotes do real work. Fn. 8 says the point is not epistemological: it is not that we cannot know what it is like, but that forming the conception at all requires taking up the viewpoint. Fn. 11 extends Kripke on why a necessary mind-brain relation would still appear contingent.
Concepts
- Subjective character of experience: what it is like for the subject. Fn. 6: “what it is like” means “how it is for the subject himself”, not “what it resembles”.
- Point of view: a type, shared by sufficiently similar beings, not an individual’s privacy.
- Objectivity as a direction: understanding can travel toward the objective without an assumed end point.
- Perceptual, sympathetic and symbolic imagination (fn. 11): imagining a mental state sympathetically and its brain state perceptually makes their separation seem conceivable, even if it is necessarily impossible.
- Objective phenomenology: describing the structure of experience in terms comprehensible to those who cannot have it.
Connections
LIT-056(Butlin et al., 2023) defines its sole target, phenomenal consciousness, as “something it is like”, which is this paper’s criterion. NOTE-052’s Concepts section records the definition. Butlin et al. get from functional indicators to that target by assuming computational functionalism. Nagel’s C2 is the argument that no such step follows from an analysis of the concept. His fn. 2 is also why it cannot be ruled out either.- NOTE-052’s “quality space”, the similarity space of phenomenal qualities, is a structural description of experience. Nagel’s objective phenomenology names structural features of perception as the likeliest part of experience to admit such a description. The resemblance is mine, not either paper’s.
- Cited within: Smart, Lewis, Putnam, Armstrong and Dennett as the reductive analyses (fn. 1); Kripke’s Naming and Necessity (fn. 11); and Davidson’s “Mental Events” (fn. 12). None of these is in the record.
Bearing on the record
For ML, this is the paper that says what a question about machine consciousness is a question about, and why behavioural or functional evidence cannot close it by itself. It gives the record the vocabulary for keeping two claims apart:
- A system has the functional organisation a theory associates with consciousness.
- There is something it is like to be that system.
LIT-056 is careful to present its indicators as raising a probability, not
settling the question. This paper is the reason that care is needed. The paper
supports no practice or theory in the anthology’s sense, and none should be
drawn from it.
Limitations
- The central criterion is stipulated, not argued. A reader who doubts that “what it is like” picks out anything, as eliminativists do, is addressed only by the Martian thought experiment.
- The objective-phenomenology proposal is one page with no worked instance beyond the dismissal of “red is like the sound of a trumpet”.
- “Physical” is left undefined except as objective (fn. 15). So the claim that experience resists physical description comes close to following from the definitions.
- Its examples of reduction are 1960s–70s identity theory. It does not address later functionalist or representationalist accounts, because it predates them.
Open questions
- Nagel concedes in fn. 8 that understanding across species varies by degree. Is objective phenomenology the same project as learning a structural, similarity-space description of perception, and what would it leave out?
- Fn. 2: is there anything that behaves like a person but has no experience? Nagel says concept analysis cannot answer this. The question is what could.
Text read
The whole paper, including all fifteen footnotes, from a web transcription (philosopher.eu) of the version reprinted in Nagel’s Mortal Questions (Cambridge University Press, 1979). Footnote 1 refers to “chapter 11 above”, which marks it as the reprint. The transcription drops the footnote markers and the original page numbers. So claims above are located by footnote number, not by page, and the text was not collated against the 1974 Philosophical Review printing. The transcriber appends a quotation, attributed to Nagel’s The View from Nowhere (1986), that credits the phrase to Sprigge and to Farrell (1950). I did not check it against that book.