More on Explaining a Gap

Gilbert Harman
Princeton University

February 13, 2015
There is a Danish translation of this paper.

In (Harman 2007) I argued “that a purely objective account of conscious experience cannot always by itself give an understanding of what it is like to have that experience.” Following Nagel (1974), I suggested that such a gap “has no obvious metaphysical implications. It [merely] reflects the distinction between two kinds of understanding,” objective and subjective, where subjective understanding or “Das Verstehen” (Dilthey 1883/1989) of another creature’s experience involves knowing what it is like to have that experience—knowing what sort of experience of one’s own would correspond to the other creature’s experience.

In the linguistic case, one understands one’s own words in the sense that one is “at home” with them. One best understands what others say by translation into one’s own way of using language. So it seemed to me useful to think of understanding another’s experiences as a kind of translation into one’s own. I suggested that we might be able to narrow the explanatory gap via an objective account of translation, e.g. in terms of functional relations. Such an account could be used in order to discover what it is like for another creature to have a certain objectively described experience given the satisfaction of two requirements. “First, one must be able to identify one objectively described conceptual system as one’s own [an identification that is not itself fully objective]. Second, one must have in that system something with the same or similar functional properties as the given experience.”

With this brief background I would like first to discuss three commentaries on (Harman 2007) recently published in this newsletter. I then want to say something about the featured article in this issue, by Franklin, Baars, and Ramamurthy, which raises a somewhat different issue about whether a machine could have “the subjective experience of qualia …phenomenal qualia …”


Ledwig (2007) points to an unclarity as to exactly what is involved in subjective understanding or Das Verstehen and my suggestion that a special case of such understanding is the understanding one has of one’s own language. What is meant by “one’s own language”. Might it be a language like English, which has a history and a number of variants or dialects? Or is it a particular idiolect or (as linguists say) I-language?

I was thinking of a language in this second sense, one’s I-language, the language in which one is at home, whose principles are internalized and not usually known to one in any serious way. Language in the social and historical sense is varied, containing words with which one is not familiar or which are used in different ways from the way one uses them. A language in the social and historical sense is not something one could be fully at home in. To understand what someone else says one must be able to find a translation or equivalent expression in one’s I-language, one’s particular way of using language.

Consider Ledwig’s worry that

it is not obvious to me whether a proper Verstehen in Harman’s view also involves knowing where a certain meaning has come from or not. Or is a proper Verstehen also reflected by knowing under what kind of conditions one uses an expression? As a native German who has English as a second language, I now know under what kind of conditions it is appropriate to use the word ‘gorgeous’ in American English, but I still find it truly surprising and puzzling that …[it] just applies to one sex.

My response is that the sort of understanding I had in mind need not involve any explicit knowledge of the conditions under which expressions are or are not appropriately used. The typical speaker of American English need not have considered the question whether the word “gorgeous” appropriately applies only to one sex, for example. For such a speaker, the understanding of this word is internalized, second nature.

Ledwig observes that an explanation of this fact about how “gorgeous” is used in American English might properly receive “not only a historical explanation …but also a cultural one.” She suggests that “a historical or cultural explanation of the term would have helped me to understand its usage fully.”

My response is that there are two ways of understanding the use of a word, one in which one is at home with using the word, as she was not completely at home using “gorgeous”, the other in which one has a more objective understanding of the use of the word, involving explicit knowledge that it tends to be appropriately used only of one sex, for example.

She asks whether there can be “partial Verstehen or whether Verstehen always has to be complete,” taking her understanding of “gorgeous” “to suggest that partial Verstehen is possible.” I agree. One’s subjective understanding of someone else is often partial in this way.

Concerning my suggestion that the explanatory gap reflects the difference between objective and subjective understanding, Ledwig wonders “whether the explanatory gap is inevitable.” She notes various ways in which we may be able to use objective empirical methods to help gain understanding of others. For example, in order to gain an understanding of what it is like to be a member of the opposite sex, one might take on the identity of someone of the opposite sex, “one can even have a sex-change operation.” She discusses a number of other cases, including trying to help a congenitally blind person gain an understanding of what it is to experience color surfaces: “one could enhance the texture of these surfaces to the blind.”

Her interesting discussion of these and other cases is quite suggestive, while it seems to me to support the idea that the explanatory gap arises from the difference between objective and subjective understanding.


Worley (2007) appears to disagree with this last discussion of Ledwig’s, when she says, “some concepts (the objective, third personal ones) are available to anyone with appropriate exposure and acculturation, and others are not.”

Worley adds, “It is the status of these peculiarly first personal phenomenal concepts that Nagel finds mysterious and the appeal to Verstehen and failure of translation does not help resolve this mystery.” I am not sure I agree with this. What Nagel finds mysterious (if that’s the right word) is how to relate the two sorts of concepts or ways of understanding things. My own suggestion, repeated in the next section, is that we might make some progress on resolving this mystery if we were able to arrive at an objective understanding of what it takes for good translation between different subjective outlooks.


Nagasawa (2007) argues that “Harman’s formulation of the explanatory gap seems therefore to face the following difficulty: Either (i) it is irrelevant to the cogency of physicalism or (ii) if it is relevant, any talk of translation is otiose.” I agree with (i), indeed I explicitly said that the explanatory gap “has no obvious metaphysical implications” and “reflects the distinction between two kinds of understanding.” On the other hand, with respect to (ii), I do not think that talk of translation is completely otiose in this connection.

As Nagasawa points out, simply knowing what it is like to undergo a physical process objectively described does not by itself eliminate the explanatory gap, because we may still wonder why that objectively described process is associated with this subjective experience. Merely having a way to translate between a creature’s experiences and one’s own does not eliminate the gap, because the creature might be oneself and the gap is still there in one’s own case.

Now suppose one had in addition a completely objective account of “translation” from the possible experiences of a creature to those of another, an account in terms of objective functional relations, for example. And suppose in addition that one was able to identify a particular objectively described mental system as one’s own. Then it seems to me one might have some sort of objective understanding of what it is like to have various experiences. I agree that this understanding need not be completely objective, since it would depend on being able to identify a particular system as one’s own, which is not a purely objective matter. It is not a purely objective matter which creature is oneself.

Phenomenal Qualia

Franklin, Baars, and Ramamurthy suggest that it may be possible actually to build a machine capable of consciousness. I agree that, if by appeal to similarities between one’s own functioning and behavior and that of the machine, one may find that it’s possible to translate between events in some machine and one’s own experiences in a way that satisfies certain conditions, then one can attribute consciousness to that machine and can even know what it’s like to be a creature with those events occurring.

On the other hand, as the authors note, the lack of such a translation for a given machine would not rule out consciousness—that there is something that it is like to the machine to be such that machine; it would only rule out our being able to know in the relevant way what that is like.

The authors take the question whether a machine can be conscious to be the question whether a machine can have “the subjective experience of qualia ... phenomenal consciousness...” I assume that by “qualia” they mean certain experienced qualities of perceived objects. But some philosophers use the word “qualia” to refer to intrinsic qualities of the experience, intrinsic qualities of which one is allegedly aware in having the experience. I deny that one is aware of intrinsic qualities of conscious experience. I say that to think we are aware of such intrinsic qualities of experience is to confuse qualities of an experience with qualities of the object of that experience.

The object of a conscious experience is an “intentional object”—an apparent object that may not really exist, like the dagger that MacBeth sees before him, or the pink elephants a drunk sees, or the Fountain of Youth that Ponce de Leon was looking for. The fact that the Fountain of Youth does not exist does not entail that Ponce de Leon wasn’t looking for it. Similarly for the drunk’s pink elephants and MacBeth’s dagger. The drunk’s elephants are pink and MacBeth’s dagger drips with blood, but the drunk’s experience isn’t pink and MacBeth’s experience isn’t dripping with blood. It is a fallacy (the sense-datum fallacy) to suppose that features of the intentional object of experience are features of the experience. [Harman (1990/1999) discusses this further. Block (2007) argues the other side.] I am not saying that Franklin et al. commit this fallacy; only that some philosophers who use the “qualia” terminology do so.

Finally, I do not understand the authors’ suggestion “that providing perceptual stability and coherency is one fitness benefit of phenomenal consciousness.” I understand how providing perceptual stability and coherency benefits fitness. But I do not understand how this is provided by phenomenal consciousness, no matter how that is interpreted. Maybe what the authors mean merely is that perceptual stability is a feature of our perceptual consciousness, so a creature’s having perceptual stability makes the creature more like us and so more like a conscious being. To that I agree.


Block, N. (2007). “Consciousness, Accessibility and the Mesh between Psychology and Neuroscience,” Behavioral and Brain Sciences 30: 481-548.

Dilthey, W. (1883/1989). Introduction to the Human Sciences (R. Makkreel & F. Rodi, Eds.). Princeton, NJ: Princeton University Press. (Original work published 1883)

Franklin, S. et al. (2008). “A Phenomenally Conscious Robot?” American Philosophical Association Newsletter on Philosophy and Computers 8.1.

Harman, G. (1990/1999). “The Intrinsic Quality of Experience,” Philosophical Perspectives 4 (1990): 31-52; reprinted in Harman (1999), pp. 244-261.

Harman, G. (1999). Reasoning, Meaning, and Mind. Oxford: Clarendon Press.

Harman, G. (2007). “Explanation an Explanatory Gap,” American Philosophical Association Newsletter on Philosophy and Computers 6.2: 2-3.

Ledwig, M. (2007). “To Understand the Understanding—das Verstehen zu Verstehen: A Discussion of Harman’s ‘Explaining an Explanatory Gap,” American Philosophical Association Newsletter on Philosophy and Computers 7.1: 16-18.

Nagel, T. (1974). “What Is It Like to Be a Bat?” Philosophical Review 83: 435-50.

Nagasawa, Y. (2007). “Formulating the Explanatory Gap.” American Philosophical Association Newsletter on Philosophy and Computers 7.1: 15-16.

Worley, S. (2007). “Verstehen and the Explanatory Gap,” American Philosophical Association Newsletter on Philosophy and Computers 7.2: 15-16.