It's a philosophical truism that human conscious experience is unified: If you're at a bar, hearing music, tasting beer, and feeling pleasantly relaxed, those experiences don't occur merely side by side. They are joined together into an integrated whole, an experience of music-with-beer-with-relaxation.
I'm not sure this truism is correct. As I suggested in an earlier post, experiential unity might be an artifact of introspection and memory: When we introspectively notice that we're experiencing music, beer, and relaxation all at once, we thereby bind those experiences into a whole. Likewise, when we remember such moments, we reconstruct them as unified. But it doesn't follow that those experiences, even if they all occurred simultaneously in you, were unified rather than transpiring separately. Experiences of music, beer, and relaxation might have all being going on inside of you, no more joined together than those experiences are joined with the similar experiences of your friend across the table. Simple co-occurrence doesn't entail experiential unity.
If this possibility is coherent, then introspection and memory can't establish that experience is always unified. At most, they show that introspected and remembered experiences present themselves as unified. But that leaves open the status of unintrospected, unremembered experiences. Unity becomes difficult to verify by standard phenomenological methods.
But the issue needn't be intractable. We just need to approach it less directly, for example by exploring what follows from a well-established theory of consciousness. If some well-motivated Theory X implies unity (or disunity), that would provide reason to accept its conclusion.
I'll now present a candidate Theory X. I'm not suggesting that this is the right theory of consciousness! For one thing, it's simplistic. I'm sure the mind is much more complicated than I'm about to say. I offer this theory only as a proof of concept. There could be a theory of consciousness with massive disunity as an implication.
This theory combines Global Workspace Theory and Recurrent Processing Theory. According to this hybrid, Global Workspace Theory governs attended experiences -- those targeted by introspection or reconstructed in memory -- while Recurrent Processing Theory governs unattended experiences.
The mind, on this picture, is composed of many separate "modules" that work mostly independently, connected by a workspace where a small amount of attended information is shared globally. There's a visual module, an auditory module, modules for motor activity, episodic memory, and so on. When we attend to something -- say, the taste of beer -- the information from the relevant module is broadcast into the Global Workspace, where it can be accessed by and influence processes in all the other modules. When unattended, the information stays local.
Here's one illustration of this type of architecture:
Orthodox Global Workspace Theory holds that only what is broadcast into the workspace is conscious. Theory X alters that assumption. Many people hold that conscious experience vastly outruns attention. Many people hold, that is, that you can experience the hum of traffic in the background when you're not attending to it, and the feeling of your feet in your shoes, and the leftover taste of coffee in your mouth, etc. -- all in a peripheral way, simultaneously, when your focus is elsewhere. Theory X, drawing on Recurrent Processing Theory, holds that such processes are conscious whenever there's enough cognitive activity of the right sort (recurrent processing, for example) in the modules, even without global broadcast.
The picture, then, is this: We have multiple sensory (and other) experiences all running simultaneously, each with enough cognitive processing to be conscious, but few of which are selected for global availability through attention.
Is there reason to think these modular processes are unified with one another? I see no reason to think so, if they're genuinely modular -- that is, if their processing stays local, exerting little influence elsewhere. The taste-of-beer processing stays in the tasting module. The sound-of-music processing stays in the auditory module. No link up. No straightforward causal, functional, or physiological basis for a unified experience of beer-with-music rather than, separately, an experience of beer and an experience of music.
When we introspect the beer and music simultaneously, we pull both into the Global Workspace, and there they unify. We might then mistakenly think they were unified all along, but that's an illusion of introspection. It's an example of the "refrigerator light error", the error of thinking that the light is always on because it's always on when you open the door to check.
On this model, disunity is the normal human condition. Our experiences are fragmented, except when we pull them together through attention. We just don't realize that fact because, so to speak, we only attend to what we attend to.
Two caveats:
First, this is probably not the right model of consciousness. But I don't think it's unreasonable to wonder if the correct model is similar enough to have the same implications. If so, we can't simply accept the unity of consciousness as a given.
Second, the recurrent peripheral, modular processes that don't make it into the workspace might not be determinately conscious. They might be only borderline conscious, in the indeterminate middle between consciousness and nonconsciousness, like a color can be indeterminately between green and not-green. This opens a third possibility, alongside unity and disunity: unity among the determinately conscious experiences with a hazy penumbra of indeterminate experiences that remain disunified. (There are further possibilities beyond these three; but save them for another day.)
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