Pain Sense-datum theories

Standard perception (exteroception) can be analyzed as involving the perception (act) of a public object. The perceptual act on the part of the perceiving subject, in turn, is analyzed as involving an experience which typically induces conceptual categorization, i.e., application of concepts to the object of perception and its qualities — not to the experience. Thus perceptual experiences seem transparent to the perceiver, who may be said to perceive the extramental reality directly, without first perceiving or somehow being aware of the experience itself or its qualities. This view is supported by common sense and is typically called naive or direct realism.

According to the indirect realists, this directness is an illusion; we are in fact directly aware of experiential intermediaries, and we perceive the extramental world only indirectly, in virtue of being directly aware of these intermediaries. Most early indirect realists (e.g., Moore 1903, 1939; Russell 1912; Price 1950) thought of these intermediaries as phenomenal or mental particulars, typically called sense-data. Consider a hallucination of a red apple. Intuitively, the person having the hallucination seems to see something. This something is not, of course, an apple. But it is an object, according to sense-datum theorists, which is shaped like an apple and is really red. It is a sense-datum, a phenomenal (mental) individual which really has the qualities that it visually appears to have. Sense-data, however, are no ordinary objects: they are private, subjective, self-intimating, and the source of incorrigible knowledge. According to sense-datum theorists, sense-data are internal to one’s consciousness: they are not before one’s sense-organs. These theories claim that there is a hidden act-object structure in the perceptual awareness itself. Every perceptual awareness involves the act of being aware of phenomenal objects that characterize this perceptual awareness, whether or not this awareness is an hallucination or a veridical perception of external objects.

So on sense-datum theories, one perceives external objects and their qualities, indirectly by directly perceiving (being aware of, or acquainted with) sense-data internal to one’s consciousness that resemble in various degrees the physical objects that cause them. According to sense-datum theorists, however, we are rarely, if ever, aware of this indirection in ordinary (veridical) exteroception. It is only critical philosophical reflection on features of perceptual awareness that reveals that the indirection must occur. The importance of pain and other (intransitive) bodily sensations lies in the fact that the indirection seems to be easily revealed introspectively as is shown by our unwillingness to identify the pain we attribute to body parts with anything physical in those parts.

Whatever merits sense-datum theories might have with respect to genuine perception and misperception, its attraction seems undeniable when it comes to its treatment of pains and other “intransitive” bodily sensations like itches, tickles, tingles, etc.^[4] According to many sense-datum theorists, pains are paradigm examples of phenomenal individuals, mental objects with phenomenal qualities whose existence depends on their being sensed or felt, and thus are logically private to their owners who feel them. This position presumably explains why we have the act-object duality or ambiguity in pain talk that we discussed earlier: pains qua localizable objects cannot exist without the corresponding acts, i.e., without someone’s acts of experiencing them (Broad 1959).^[5] In other words, the concept of pain plausibly applies to both the object part of the act-object pair and to the act of being directly aware of these objects.

The puzzle of locating pains in body parts can be treated in more than one way within this framework. The most straightforward way is simply to take the phenomena at face value and say that pains as mental objects or sense-data are literally located where they seem to be located in body parts or even in empty space where one’s limb would have been, say, before the amputation. That pains are mental particulars and depend for their existence on being sensed apparently does not logically preclude their being capable of having, literally, a spatial location (see Jackson 1977 for this line).^[6]

A second and more popular way of handling the location problem is to say that even though pains cannot literally be located in physical space, they can have location in a phenomenal space or field that is somehow isomorphic or systematically related to their counterparts (say, tissue damage) in physical space. In fact, this move would also work for visual sense-data that require some spatiotemporal framework. In the case of bodily sensations, this phenomenal space is sometimes called one’s somatic field by analogy to a visual field that maps onto physical space (Price 1950).