Loosely defined, the term "qualia" usually refers to the phenomenal aspects of mental experience. Examples from the Stanford Encyclopedia of Philosophy should suffice: “I run my fingers over sandpaper, smell a skunk, feel a sharp pain in my finger, seem to see bright purple, become extremely angry” (Tye, “Qualia”). To undergo any of these experiences, most of us would agree, would entail a very particular feeling. Quite apart from the simple recognition of damage from sandpaper, or the mere identification of a particularly bright shade of purple, there seems to be a qualitative - phenomenal - aspect to each of these mental affairs. Simply put, there is something it is like for you or me to have an experience. Thomas Nagel, Keith Campbell, and Frank Jackson each argue that qualia, in this broad sense, must exist (Nagel, “What Is It Like To Be A Bat?”; Campbell, “A Critique of Central-State Materialism”; Jackson, “Epiphenomenal Qualia”).
However, exactly what "qualia" means to each thinker differs substantially, and the conclusions they draw vary accordingly. Nagel's analysis allows for qualia to be essentially physical properties of a purely physical realm of the mind and to play a causal role in the physical events of the universe; thus, his analysis of qualia poses no threat to the physicalist doctrine that everything is physical (Stoljar, “Physicalism”). Campbell and Jackson deny that qualia are physical; thus, their analyses of qualia seek to falsify the physicalist premise. This paper contends that Campbell's and Jackson's analyses carry no ontological weight, rely on a primary intuition with unclear origins, and lead to highly counterintuitive and worrying consequences. Nagel's analysis, in contrast, necessitates none of the suspect results that come with Campbell's and Jackson's claims. Consequently, we should take Nagel's account of qualia - which does not show physicalism to be mistaken - to be overwhelmingly preferable.
Nagel approaches the question of qualia by examining what he terms “the subjective character of experience” (323). He clarifies exactly what he means when referring to this subjective element by inviting us to imagine what it would be like to be a different form of life. A bat's experience when it uses sonar to sense the world, for example, must be completely dissimilar to anything that a human can experience (Nagel 324). Though we may imagine what it would be like “to behave as a bat behaves,” Nagel argues, we cannot imagine what it is like to be this organism (324). Furthermore, it seems to Nagel that physical science as it stands today cannot help us understand what it is like to be something that we are not. A bat's qualia - Nagel's what-it-is-likeness - are completely inaccessible to humans through any third-person analysis because their inherently subjective element would necessarily be lost through any objective inquiry (Nagel 323, 326).
Though Nagel admits that we might never be able to experience a bat's qualia, he sees no reason to deny that there is nonetheless a fact of the matter. Human conception and the lack thereof, he believes, have no implication to what is real. Indeed, Nagel argues that “to deny that the reality or logical significance of what we can never describe or understand is the crudest form of cognitive dissonance” (325). This subjective realism is crucial to his analysis: it allows him to treat the problem he raises as an epistemic one, with no ontological commitments attached. Facts presently unintelligible through objective physical analysis need not be non-physical. Indeed, qualia could yet be physical in spite of the fact that “we have at present no conception of what an explanation of the physical nature of a mental phenomenon would be” (Nagel 322). Accordingly, Nagel refuses to denounce the physicalist position that everything, including qualia, is physical (328).
In contrast, Campbell's account of qualia entails exactly what Nagel refuses to commit to, that physicalism is false. This follows from his claim that “the enjoying or enduring of phenomenal properties is not a physical affair” (Campbell 338). Because Campbell's phenomenal properties - qualia - are non-physical, Campbell's analysis stands in stark opposition the belief that everything is physical; physicalism, to Campbell, must be mistaken. To support this view, Campbell presents us with a critique of the Causal Theory of mind. This widely-accepted theory holds that inner mental states cause our outward behaviour (Campbell 333). For example, in the case that my finger is burned, the Causal Theory holds that certain “components” arise in my mental state: these include “awareness” that my finger is burned and “desire” that this awareness stop immediately (Campbell 333). Mental components such as these combine to form a causal chain that results in my behaviour: for example, I might decide to run my finger under cold water. Campbell agrees with the Causal Theory that these mental components are entirely physical, writing that “the brain's activities of a physical kind all occur in accordance with physical laws” (337). Because of their physical nature and their functional role in determining behaviour, we may call these mental components "physical-functional properties."
