Phillips’s solution: Commitment 1

That experience has a temporal field is, Phillips claims, demonstrated by the fact that we are able to perceive the movement of some objects (or visual stimuli more generally) but not others. We can, for example, see the second hand sweep across the clock face, but the hour hand never appears to move. We only ever notice that it has moved. According to Phillips,

What this shows is that there is an upper bound to the stretches of time over which we can directly apprehend complete events and processes. As a simple model, we can think of our experience as having a ‘temporal field’, and of there being limits to the extent of the field, say 300ms. (Phillips 2011a: 817)

The thought is that we perceive the world through a small temporal window of about 300ms. Since a positional change between indiscriminable positions appears as no change at all, the positions of a moving object must be discriminable within this 300ms window in order for the object to be seen to move. Only then is its positional change ‘genuinely an object of experience’ (2011a: 813). So either the positions are discriminable, in which case motion is represented as occurring over the 300ms duration, or else the positions are indiscriminable, in which case no motion is represented at all. This is the idea of the temporal field of experience.

Before moving on to Commitment 2, I want to show why the atomist qua retentionalist cannot accept this notion of the temporal field. It might not be obvious why this is the case. After all, the retentionalist claims that experience has a temporal field in the sense that experience is capable of representing temporally extended phenomena. This is the notion of what is sometimes called the ‘specious present’.

As Phillips recognises, an atomist could be a retentionalist, meaning that they could hold that although the experiential state is momentary, its content is extended. And if its content is extended – if it is an experience of an extended event – then, assuming the experience is veridical, the object will be an extended event. So it seems that the atomist could accept Commitment 1, and hold that the object of experience is the 300ms change. There are problems with this view, though. Let’s say an observed object moves between two minimally discriminable positions just within the 300ms timeframe. If Phillips’s notion of the temporal field is correct, the positional change will be a ‘genuine’ object of experience. But it would be what we may call a borderline motion experience. The positions are minimally discriminable, so if it moved any less in that 300ms, its positions would be indiscriminable and so it would not be seen to move. The problem is that, when understood within a retentionalist framework, this will either require positing an unrealistic delay-to-consciousness, or else it will require backwards causality.

For the retentionalist, experiential states are instantaneous, even though they can represent occurrences that take place over extended periods. So the retentionalist will posit an instantaneous experiential state (or a series of many such states) with the content of the object’s positional change over a 300ms timeframe. But we may ask: when exactly does the (first) experiential state with this content occur? It must occur either prior to or upon completion of the 300ms positional change. If it occurs prior to the completion of the 300ms positional change, then the object of that experience will be an event that has yet to complete. In other words, we would be having an experience of an event that is partly in the future.7

To avoid this sort of backwards causality, the retentionalist is forced to hold that we experience the change upon its completion. This means that we would have been observing the moving object for (just under) 300ms before being able to see its motion. This is an unfeasibly long delay. Dennett (1991) considers a similar proposal in relation to the phi illusion. The phi illusion works by flashing two dots in different locations in quick succession. Subjects report seeing a single moving dot; the intervening motion is apparently ‘filled in’. This result is problematic. Ruling out precognition, there are two natural lines of explanation. One is to say that the subject has a false memory of seeing the intervening motion: they believe they saw the motion, but they are mistaken. The

brain is merely telling the story that makes the most sense of what has just been experienced. This is what Dennett calls the ‘Orwellian’ hypothesis. The other is what he calls the ‘Stalinesque’ hypothesis. This time, instead of forming a false memory about what was experienced, there is a delay to consciousness. This allows time for both dots to be sub-personally registered and for the brain to then decide what to ‘fill in’.

Over very short timescales, the Stalinesque hypothesis might seem fairly plausible. But, Dennett argues, all plausibility is lost when we consider Kohlers and von Grünau’s (1976) version of the phi experiment, where there is 200ms between the spots:

Suppose we ask subjects to press a button “as soon as you experience a red spot.” […] Could it be that there is always a delay of at least 200msec in consciousness? No. There is abundant evidence that responses under conscious control, while slower than such responses as reflex blinks, occur with close to minimum latencies (delays) that are physically possible. After subtracting the demonstrable travel times for incoming and outgoing pulse trains, and the response preparation time, there is not enough time left over in “central processing” in which to hide a 200msec delay. (Dennett 1991:121-2)

If there’s no chance of finding a spare 200ms for the Stalinesque delay, there’s certainly no chance of finding a spare 300ms for the retentionalist trying to accommodate Commitment 1. Contrary to Phillips’s earlier comment, then, Commitment 1 is unworkable within a retentionalist framework.

From here on, I will restrict my attention to considering the prospects of Phillips’s argument within an extensionalist framework. This is what we are really interested in anyway; this is what, if it were to succeed, would undermine the conclusion from Chapter 2 (that questions of personal and experiential identity are empty).