Ian Phillips "Hallucinating Silence"
1. In his recent discussion, 'Hearing Silence' (2008: Ch. 14), Sorenson claims that we can have veridical hallucinations of silence.
"Consider a man who experiences auditory hallucinations as he drifts off to sleep. He "hears" his mother call out his name, then wait for a response, and then call again. The cycle of calls and silence repeats eerily. As it turns out, his mother has unexpectedly paid a late-night visit and is indeed calling out in a manner that coincidentally matches the spooky hallucination." (269)
Sorenson also introduces Audrey.
"Audrey ... lives in a noisy environment and so has never experienced silence. Audrey ... wants to experience silence and so constructs a soundproof chamber. When she enters the chamber, Audrey learns something: what it is like to hear silence... Audrey is introspecting an absence of auditory sensations while perceiving an absence of sound ... an auditory gap that originates through healthy hearing of an external state of silence." (271)
In all this, Sorenson seems quite right. We allow for hallucinations of silence in cases like the above. Moreover, there is something it is like to be Audrey as she enters her soundproof chamber, and therein what Audrey is aware of is the absence of auditory sensations.
2. All this raises a puzzle, however. For consider deafness about which Sorenson says the following.
"When you become aware that you are ... deaf ... you are introspecting an absence of sensations. For you no longer perceive anything. Introspection is your only remaining means of detecting the absence." (271)
According to Sorenson, introspectively, deafness is precisely akin to Audrey's experience in her soundproof chamber. Thus,
"DIST Mere reflection on her experiential situation alone is insufficient for Audrey to distinguish her experiential situation in the soundproofed room from her experiential situation on being rendered profoundly deaf."
Now, if Sorenson is right that we can hallucinate silence, then Audrey can be introduced to the phenomenology of silence without leaving her noisy world. The criterion of success here is very plausibly the following. If we so manipulate Audrey (say, neurally) that her situation is, subjectively, indiscriminable from the perceptual situation that she would be in within her soundproofed room, she will be undergoing an hallucinatory experience of silence.
But here something has gone wrong. For by DIST, were Audrey to be rendered profoundly deaf, she would be in a situation which was, subjectively, indiscriminable from her experiential situation in the soundproofed room. But by the plausible criterion just given, this means that rendering Audrey profoundly deaf is sufficient for her to be hallucinating silence. That cannot be right, however, since we have absolutely no inclination to regard the profoundly deaf as perpetually hallucinating silence.
3. My paper dissolves this puzzle by carefully considering the phenomenon of hallucinating silence. I do not deny, what Sorenson's example amply demonstrates, that we sometimes hallucinate silence. However, a special and unnoted feature of Sorenson's example is that it involves hallucinating silence between calls. There is an important difference, I suggest, between hallucinating or hearing gaps or pauses and the supposed phenomenon of simply hallucinating or hearing silence. Simply experiencing silence is nothing more than lacking auditory experience; nonetheless we sometimes can hear silence in a way which goes beyond merely lacking auditory experience in virtue of hearing temporally separated sounds.[4, 5]
Such a picture is obscured by an assumption prevalent in the literature on temporal experience that we must explain the structure of the stream of consciousness in terms of what is true of the stream at particular moments or over tiny durations.(6) Reflection on the puzzle above shows that we must reject this assumption. The limits to hallucinations of silence precisely mark what we might think of as the auditory, temporal analogue of the visual, spatial field of vision and one of the things that we might think of as the specious present.
4. With this new picture in play, our original puzzle is resolved as follows. Note that DIST talks about Audrey's "experiential situation". It does not involve any commitment to her having auditory experience. As such we should accept DIST but clearly distinguish between:
(a) Audrey's experiential situation when engulfed in silence; and
(b) Audrey's experience, if any, when engulfed in silence.
We are prepared to attribute experience of silence only in cases where Audrey also has experience of separated sounds. Here what distinguishes hearing silence from the mere absence of experience is the experienced surrounding sounds. Thus, the fundamental explanatory unit is the whole experience of the separated sounds. In virtue of these, we hear the interleaved silence.
These situations alone afford the possibility of corresponding hallucinations. One cannot hallucinate silence over long periods. Given this, the criterion of success for giving Audrey an hallucination employed above only counts as such when Audrey cannot discriminate her experiential situation from a situation in which she is perceiving a pause. Clearly, this criterion does not commit us to claiming that the deaf permanently hallucinate silence for the deaf are not permanently hearing pauses!
Hearing a pause is not experientially akin to brief deafness. Over certain courses of experience what is true of sub-parts of the course is to be explained in terms of what is true over the whole course (and not vice-versa). This grounds a genuine difference between our experiential situation when we hear a pause and our situation where we simply lack auditory experience ñ in the former case alone are we experiencing two separated sounds throughout the whole experience. Not so if we are deaf.
5. Reflection on hallucination helps us get clear about the following argument.
(i) If we hear, we hear sounds.
(ii) Silence is the absence of sounds.
(iii) Thus, we cannot hear silence.
Sorenson rejects (i) on the basis that we hear silence. I endorse (i). Nonetheless, (i) does not preclude our hearing silence. We can hear certain silences, pauses, in virtue of hearing separated sounds. We can never simply hear silence for there is nothing experiential to distinguish that supposed phenomenon from deafness. That is why the deaf are not perpetually hallucinating.
 DIST lies behind the case of the wounded soldier who is unable to tell whether he has gone deaf or is merely hearing silence (Sorenson 2008: 268).
 Cf. Martin's (2006) claim (II), whose analogue here is: "The notion of an auditory experience of silence is that of a situation being indiscriminable through reflection from a veridical auditory perception of silence as such.î"
(3) One might claim that a functioning or "healthy" auditory system was necessary for hallucination. However, there is abundant psychiatric evidence that those deaf from a very early age, and perhaps even from birth, can hallucinate genuine sounds.
(4) Compare how we see doughnut holes as such only so long as we see the inner circumference of the doughnut - bring the doughnut close enough so you can no longer see those edges and you cease to see the hole as such.
(5) We hear silence in other ways, but all such ways involve hearing silence in virtue of hearing sounds.
(6) Traditional specious present and memory theories of temporal awareness attempt to understand temporal
experience within the strictures of this assumption. For discussion see Soteriou (2007) and Phillips (2008)
(7) Equivalently: All auditory experiences are experiences of sounds.