Such an analysis has led us to postulate protophenomena as the elementary constituents of phenomena [1, 2]. Each has the property of elementary (irreducible) subjectivity. Very simple examples of protophenomena include the experience of a spot of color at a particular location in the visual field and the feeling of pressure at a particular location on the skin. However, there are much more complex and subtle protophenomena, including elementary components of recognitions, judgments, expectations, intentions, moods and so forth. Further, protophenomena are very ``small,'' in the sense that changes in the activity of individual protophenomena will not typically affect the macroscopic phenomenal state; nevertheless the state of consciousness is no more than the sum total of the states of all the protophenomena.
Protophenomena are postulated to be associated with activity sites in the brain, the ``activity'' (degree of presence in consciousness) of a protophenomenon corresponding to some physical variable at that site. (Protophenomena and their activity sites need not be discrete, but that seems the most likely possibility at this time.) There are a number of candidates for the activity sites, but their identity remains an open question. Some of the possibilities include synapses, neural somata and dendritic microtubules, but their exact identity is not crucial for the theory of protophenomena.
What is the ontological status of protophenomena; do they exist? It is best for now to treat protophenomena as ``theoretical entities,'' analogous to atoms when they were first hypothesized. Theoretical entities are validated by the role they hold in the theory and by their fruitfulness for scientific progress. Ultimately, we may find that protophenomena exist individually (in the same way that atoms were found to exist), e.g. as properties of individual activity sites, or we may find that protophenomena exist only in the context of large numbers of activity sites, and thus that they are emergent properties, analogous to emergent physical properties. For now this is an open question.
Causal dependencies among activity sites suggest how protophenomena are integrated into a phenomenal world. Just as physical processes in an activity site depend on physical processes in other activity sites, as well as on extrinsic processes (e.g. in sensory neurons), so the activity of a protophenomenon depends on the activities of other protophenomena, as well as on variables that are not directly dependent on protophenomenal activity (i.e., variables associated with the external world). The dynamics of protophenomenal activity can be described by differential equations. In many cases the dependencies (the equations) are approximately linear, and protophenomenal activity can be described in terms of a characteristic function (often known as an ``impulse response'').
Protophenomenal dependencies establish connections among protophenomena and thereby assemble them into a phenomenal world. One way they do this is by establishing continuity through expectations. Another way is by means of conjunctive dependencies and by more complex temporal dependencies. As a result a phenomenal world may be described by a set of possible trajectories in protophenomenal state space.
In summary, the fact of phenomenal experience corresponds to a protophenomenon's activity, since that activity represents its degree of presence in conscious experience; the quality of conscious experience corresponds to the protophenomenon's dependencies, which relate it to other protophenomena.