3.2.1 The Adverbial Theory and the Problem of Perception

Some philosophers agree with the Phenomenal Principle that whenever a sensory quality appears to be instantiated then it is instantiated, but deny that this entails the existence of sense-data. Rather, they hold that we should think of these qualities as modifications of the experience itself (Level 1). Hence when someone has an experience of something brown, something like brownness is instantiated, but in the experience itself, not an object. This is not to say that the experience is brown, but rather that the experience is modified in a certain way, the way we can call “perceiving brownly”. The canonical descriptions of perceptual experiences, then, employ adverbial modifications of the perceptual verbs: instead of describing an experience as someone’s “visually sensing a brown square”, the theory says that they are “visually sensing brownly and squarely”. This is why this theory is called the “adverbial theory”; but it is important to emphasise that it is more a theory about the phenomenal character of experience itself (Level 2) than it is a semantic analysis of sentences describing experience.

Part of the point of the adverbial theory, as defended by Ducasse (1942) and Chisholm (1957) was to do justice to the phenomenology of experience whilst avoiding the dubious metaphysical commitments the sense-datum theorists take on in responding to the Problem of Perception. The only entities which the adverbialist needs to acknowledge are subjects of experience, experiences themselves, and ways these experiences are modified. This makes the theory appear less controversial than the sense-datum theory.

3.2.2 The Adverbial Theory and Qualia

When used in a broad way, “qualia” picks out whatever qualities a state of mind has which constitute the state of mind’s having the phenomenal character it has. In this broad sense, any conscious state of mind has qualia. (This is the way the term is used in, e.g., Chalmers (1996)) Used in a narrow way, however, qualia are non-intentional, intrinsic properties of experience: properties which have no intentional or representational aspects whatsoever. To use Gilbert Harman’s apt metaphor, qualia in this sense are “mental paint” properties (1990). Harman rejects mental paint, the idea of experience as involving mental paint is taken up and defended by Block (2004)).

It is relatively uncontroversial to say that there are qualia in the broad sense. It can be misleading, however, to use the term in this way, since it can give rise to the illusion that the existence of qualia is a substantial philosophical thesis when in fact it is something which will be accepted by anyone who believes in phenomenal character. (Hence Dennett’s (1991) denial of qualia can seem bewildering if “qualia” is taken in the broad sense). It is controversial to say that there are qualia in the narrow sense, though, and those who have asserted their existence have therefore provided arguments and thought-experiments to defend this assertion (see Block (1997), Peacocke (1983 Chapter 1), Shoemaker (1990)). In what follows, “qualia” will be used exclusively in the narrow sense.

The adverbial theory is committed to the view that experiencing something red, for example, involves one’s experience being modified in a certain way: experiencing redly. The most natural way to understand this is that the experience is an event, and the modification of it is a property of that event. Since this property is both intrinsic (as opposed to relational or representational) and phenomenal (that is, consciously available) then this way of understanding the adverbial theory is committed to the existence of qualia.

3.2.3 Objections to the Adverbial Theory

An important objection to the adverbial theory has been proposed by Frank Jackson (1975). Consider someone who senses a brown square and a green triangle simultaneously. The adverbial theory will characterise this state of mind as “sensing brownly and squarely and greenly and triangularly”. But how can it distinguish the state of mind it is describing in this way from that of sensing a brown triangle and a green square? The characterisation fits that state of mind equally well. Obviously, what is wanted is a description according to which the brownness “goes with” the squareness, and the greenness “goes with” the triangularity. But how is the theory to do this without introducing objects of experience—the things which are brown and green respectively—or a visual field with a spatial structure? The challenge is whether the adverbial theory can properly account for the spatial structure and complexity in what is given in visual experience. (See Tye (1984) for an attempt to respond to this challenge.)

A related objection concerns the relationship between the adverbial theory and our ordinary conception of experience. The adverbial theorist might admit that, in a sense, we are aware of ordinary objects. When one “senses redly“ if this state of mind is appropriately caused by a red thing (e.g., a tomato), perhaps this is what being aware of such an object amounts to. And it is not as if such awareness is indirect or mediated by sense-data. However, it is not at all clear that the adverbialist is in a position to secure Openness. For the adverbialist rejects not just the idea that experience has a genuine act-object structure, but the idea that the character of experience is even a presentation as of ordinary things and qualities. Qualities get into the picture, and are constitutive of phenomenal character, but not by being presented from outside of experience as qualities of things, as Openness would have it. How, then, can the adverbialist account even for the appearance of an act-object structure within experience, for Openness? It is unclear how the adverbialist is to answer this question (see Martin (1998); Crane (2000)). And so it is unclear how much of an improvement the adverbial approach, and the qualia theory, is over the sense-datum theory.