Robert Rynasiewicz, Dept. of Philosophy, Johns Hopkins University
Abstract
This paper argues that our best knowledge about how the brain represents information includes true temporal coding that is not subsequently reduce to place or population coding, entailing that space and time are on a par neuro-psychologically and that moments of consciousness cannot be instantaneous. Rather, each "moment" of consciousness (hereafter "grain") is extended not only in space, but in time as well. Thus, there is no instantaneous physical "present" in which consciousness lives, no continuous transition from instantaneous times to instantaneous times, and so on. The sense of becoming, as well as that of the past and future, and of the continuity of time is, to be sure, part of the subjective content of any grain. But this is no more mysterious than how it is that features of spatial experience (especially spatial orientation) are part of the subjective content of experience without having objective correlates in physical reality. The picture that emerges is that the spatio-temporal support of an individual's inner life comprises a discrete collection of grains. What counts as the present is an indexical matter --- each grain "sees itself" as being the present just as grains belonging to different individuals each sees itself as being "the self" as the other as "other".
The view presented is not a metaphysical conjecture, but the only empirically adequate view given our current conceptual framework unless the notions of subjectivity and the unity of consciousness are dismissed as starters rather than being explained from within the sciences. The empirical character of the graining hypothesis is such that either, sufficient ingenuity, it should be possible to discover experimental signatures for the duration of grains, or that further evidence will undermine its present prima facie empirical support. Similarly, since the graining hypothesis is merely an inductive inference, it makes no pretenses to explain how or why graining should occur. Such explanation an would be tantamount to an explanation of subjectivity itself (i.e., a scientifically robust solution to the mind-body problem). The graining hypothesis, however, has the virtue of setting in greater focus just what needs explaining, viz., in physicalist terms, how it is that a physical system can give rise to indecomposable states, especially on the spatio-temporal scale in question. In arguing toward the graining hypothesis, the paper begins by emphasizing the distinction between the psychological present as perceived and the spatio-temporal support for a given perception, reviewing some of the history of theories of time consciousness and the doctrine of the specious present. Then, it is shown how the mind-body problem becomes almost trivial given certain idealizing assumptions. Following this, the nitty-gritty of the pertinent neuro-psychology is explored, with a special emphasis on the notions of place coding, population coding, and (true) temporal coding. In conclusion, it is emphasized that despite its foundational status, physical theory is nonetheless enlightened or constrained by the totality of evidence, and that often certain possibilities can be rendered plausible or implausible by considerations that are not traditionally considered part of the data to be explained. In some cases, the considerations are so elementary that bringing them into play is simply called "epistemological analysis" as, for example, in Einstein's original critique of distant simultaneity.