Essay · Philosophy of mind

The TimeSlice Argument

When Does an Experience Happen?

Christian Lains - based on a 2012 essay

Conscious experience feels like a unified whole, yet the brain process underlying it unfolds over time. A common estimate is that even a brief conscious experience depends on at least 150 milliseconds of brain activity.

Now divide that process into three timeslices: a beginning, a middle, and an end. If the experience is one unified whole, when does it occur?

The mismatch between one experience and a three-part physical process A single continuous bar labelled "the experience — one thing" sits above three separate blocks labelled beginning, middle and end. Each block is annotated with the cost of locating the experience there: at the beginning it depends on a future that has not happened; in the middle it must hold what is gone and what has not arrived; at the end it arrives too late to cause anything. THE EXPERIENCE one thing THE PHYSICAL PROCESS beginning middle end › › ? ? ? depends on a future that hasn't happened must hold what is gone and what hasn't arrived arrives too late to cause anything
One experience above, three physical stages below, and no way to line them up.

The three answers

  1. If the experience happens at the end, once the process is complete

    Then the earlier stages are over. The experience depends on physical events that no longer exist, and it cannot have caused anything, because that work was already done without it. It would only be available as some kind of ghostly memory. It becomes the smoke, not the fire.

  2. If the experience happens at the beginning

    Then the rest hasn't occurred. Either the later stages make no difference to it, in which case they were never part of its physical basis, or they do, in which case the experience must be prescient: it must somehow know the future. What happens after is a result of circumstance, not just physical law. A meteor could hit you a few milliseconds after the beginning, in which case the experience should never have begun!

  3. If the experience happens in the middle

    Both problems at once. The present stage is asked to hold what is no longer there and what is not yet there. We can call it memory for the past and anticipation for the future, but there is no classical physical process that can be without the possibility of error. A trace that might have been wrong is not the thing it records.

If the experience is present at every stage, then either there are three independent experiences, in which case we must give up the claim that experience is a unity, or there is one unified experience persisting through the stages. In the latter case, its unity cannot belong to any single stage. It must belong to the whole process. But then the stages must be genuinely bound into one thing over and beyond the physical timeslices, rather than merely lined up as one timeslice after another. That binding is exactly what needs explaining.

Early work on this argument

I wrote this as the "TimeSlice Argument" in 2012 and shared it with a few of my fellow colleagues and my supervisor as a proposed appendix to my thesis. It sets the argument out more carefully than I have, in terms of a minimal phenomenal state Pm jointly realised by brainstates M1, M2 and M3, and then turns on a single question:

Now the question is, when does Pm occur?

— "The Source of Externalism about Phenomenal States," the cut appendix, 2012

It works through the three placements in turn and ends by concluding that we are surrounded by absurdities on all sides. The exits were available at the time. Justin Fisher had argued in 2007 that nothing mental is fixed by what is in the head at a time, and preferred a history-oriented teleo-functionalism; Dennett had run similar cases to absurd consequences and ended in eliminativism. The symmetry between those exits is what made me accept this was a deep problem rather than take one.

The current views

Rejecting the thought experiment

  1. Reject the apparent unity

    Dennett, Frankish and other deflationary or illusionist thinkers explain away the apparent unity of experience. They regard the unity of consciousness as a kind of illusion, produced by cognitive access, judgment and report rather than by a further irreducible phenomenal whole. This boldly contradicts our direct experience.

  2. Reject the extended process

    Builes and Impagnatiello reject temporal extension. Their Time-Slice Internalism is both actualist and dispositionalist: the instantaneous physical state is sufficient for experience, but is spiced up with powers that determine how it would develop.

Positive approaches

  1. Accept influence from the past

    Retentional views associated with Tye and Grush place the experienced sequence in a present state that retains the ghostly memory of what has passed. Dretske and Fisher take the externalist route: the present experience depends on a history beyond the current timeslice. But then how can experience cause anything?

  2. Accept influence from the future

    Future-dependent views associated with Phillips and Soteriou allow the beginning of an experience to depend on what comes later. The present experience is partly fixed by the future course of the process. But how might the future affect the past?

  3. Accept influence from both

    These views tend to deny that an experience can be reduced to a series of independently sufficient spacetime slices. Fusion, integration and some quantum views instead treat the slices as participating in an indivisible whole: a unified field, an irreducible cause-effect structure, or a time-symmetric quantum process.

My own view, Hypermodal Realism, broadly falls within the third positive approach. A conscious experience is one real whole across the interval: what has happened and what can still happen both help individuate it. The timeslices are genuinely fused. I develop this view on QualiaSpace, alongside Camilla Karlsen's work on Qualia Fusion Emergence.

Sources

The 2012 appendixThe 2012 thread