Biology 202
2003 Second Web Paper
On Serendip

The most ambitious and unwieldy of these questions is without a doubt the second, regarding the continuity of the physical world. This question is the realm of philosophers alone, and it has been debated since the beginning of thought. Heraclitus thought the world was in a constant state of continuous change, while Parmenides thought time an illusion, laid out eternally and unchangingly. Today this debate has become known as that between the "conventional theory of time" and the "block theory of time." (1) New names for the two camps, however, have provided no new answers, and the debate seems interminable. If the question of whether time in the physical world flows at all cannot be answered, it is certainly impossible to determine whether it flows continuously.

Philosophy must here bow out to some degree and let psychology have its turn at bat. Aristotle writes: "Whether, if soul (mind) did not exist, time would exist or not, is a question that may fairly be asked; for if there cannot be some one to count there cannot be anything that can be counted..." Aristotle is wise enough not to attempt to answer this question, but instead simply states that the answer depends on whether time exists countably in the absence of a perceiver. (2) Thus the ball is thrown very early in the game into the hands of psychologists and neurobiologists, and the question thus is transformed into the first of the three, regarding experience.

William James advocated a model of experience with continual mental states, the "stream of consciousness." He writes: "Consciousness, then, does not appear to itself chopped up in bits. Such words as 'chain' or 'train' do not describe it fitly as it presents itself in the first instance. It is nothing jointed; if flows. A 'river' or a 'stream' are the metaphors by which it is most naturally described." He explains that even when gaps seem to appear in the moments when we are aware of our awareness, such as when a loud noise surprises us, even there exists some sort of mental state and thus a continuity of experience.

This continuity, James infers, is artificially created in the mind from discontinuous events. (3) Much in the same way that our mind artificially glosses over the blind spot we have in the vision-field of each eye, (created by the break in the sheet of photoreceptors where the optic nerve enters the eye) our brain has the ability to "make up" a temporal continuity out of discrete events. Scientists describe a certain frequency of experience at which distinct events blur into a single continuous duration. This frequency of events is known as the Continuous Flicker Frequency, (CFF) at which the experience of a flickering light becomes an experience of a continuously burning light. Depending upon variables such as size of the light source and the characteristics of the observer, the CFF can vary between 2 and 80 cycles per second, (4) but the standard recognized CFF, often used in cinema to turn many still images into an illusion of a motion picture, is 60 cycles per second. Thus the answer to the question of experience's continuity is certainly that experience is continuous, or at the very least, discrete events can sometimes be transformed in perception into a single continuous event.

With this in mind, the answer to our third question, regarding the continuity of brain events, seems fairly obvious. Brain activities are, at their basis, coordinations of action potentials, and action potentials firings have beginnings and ends. Each flicker of a movie projector sets off a complex perception event, in which many neurons have discrete moments of action and then inaction. Meanwhile, we have a perception of continuous motion on the movie screen with much longer duration than any action potential's firing. Thus brain events are not continuous in the way that the experiences with which we link those events are continuous.

Now we have reached the point where the answers to our questions begin to contradict, and their reconciliation of those answers becomes the question. If we are to maintain the materialist claim that the brain is the mind, how can we reduce continuous mental events to discrete brain events? (6) The argument that we cannot reduce those mental events is called "the grain argument" of perception, and it seems prima facie to prove the ontological duality of the mind and brain.

It is often argued that the solution to the gap between the perception and objective reality is to label the perception an "optical illusion." But this trivializes the problem and relegates it to a category of problem that is much more easily solved. Often a seeming inconsistency can be solved by showing that a phenomenon thought to be cause by brain process X is really caused by brain process Y, which has the property which was lacking in X. Thus the illusion is solved. But in certain cases to which the grain argument applies, this traditional solution fails. As Robert M. Anderson Jr. writes, The [cases of temporal and spatial continuity] cannot be explained in this way...To see this consider a perception of red, X. On our schema X will be the object. X seems smooth but, by the grain argument, it is not. So we posit Y, an appearance of X which has the smoothness which X cannot have. Y in turn, however, is grounded in processes that are not smooth so again we are forced to posit Z, ad infinitum. (5) Anderson attempts to save the temporal problem from this infinite regress with the following argument:: he points out that when a light flickers at a frequency beyond 60 cycles per second, the neuronal activity is the same as if the light were burning continuously. Thus he would like to place the temporal problem in the first category of illusion discussed above, where process Y solves the problem process X could not solve. But no matter which neurons are used and how frequently, process Y here must also involve only discrete processes. Neither X nor its replacement has the needed property, and Anderson's infinite regress argument must apply.

Anderson has a solution to the grain argument with regard to spatial continuity, which involves an explanation of the overlapping system of visual receptors. But this cannot help us with regard to temporal continuity. After all, visual receptors can overlap spatially, but a certain action potential's firing cannot overlap with itself temporally. While it could be argued that an action potential could have multiple voltages traveling its length at once, or that multiple action potentials could be simultaneously sending voltages for a certain purpose, the moments when those voltages reach their target could not overlap. Faced with the conflict between continuous subjective experience and discrete external reality, we have too options. We can either (1) maintain our materialist stand and argue that this difference, like many differences between our perception and our brain, is merely an illusion that can be reduced like other differences or (2) admit that consciousness is irreducible and materialism is indefensible. But how can we plausible accept the first option? If perception is continuous and brain processes discrete, then how could physical objects produce a perceptual illusion in the gaps in which those physical objects do not exist? In those temporal gaps, when all that exists is perception, there can be reduction to physical objects. Thus the temporal continuity of experience seems to be a powerful argument against materialism..

WWW Sources

2)The Internet Encyclopedia of Philosophy: Time, Some more summary of philosophical ideas about time, focussing on the history of the discussion.

3)Classics in the History of Philosophy: William James' Principles of Psychology, William James's famous text, covering many topics in psychology and psychological philosophy.

4)Something About Flicker Fusion, A detailed look into the phenomenon of continuous perception of a flickering light.

5)The Illusions of Experience, An attempt to redefine and then debunk the grain argument of consciousness.

6) The Operating System of the Brain; Disregulation and its Remedies, An article discussing issues of neurobiological timing.

7)The Frequency of Dreams, Only tangentially related to this paper, this article discusses whether we constantly dream during sleep, which would relate to an idea of continual (i.e. totally incessant) model of experience.

8)Time to Think?, This site shows us how brain activity takes time...I'm not sure if it relate to continuity of experience, but it seems possibly important. Draw your own conclusions.

9)The Continuity of Consciousness, Another discussion of the continuity of experience, though it seems to be not too rigorous of one, more wishy washy spiritual stuff...read at your own risk.

10)The Time Percept, A student's webpaper about time's nature in reality and in perception.

11)The Brain and Time, A very useful discussion of brain and time issues, with discussions of continuity and lots of links and demonstrations.

12)Can Neurobiology Teach us Anything about Consciousness?, A long and rigorous article about the reducibility of consciousness to physical objects...a good example of the theory who's rejection might be aided by thinking about continuity of experience.

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