"One thing should be remarked here. Such a mathematical description is physically meaningless unless the way we construct time is made clear. All our judgments about time is one about events that occur simultaneously. "
Albert Einstein, in his first paper on special relativity (1905)
4-1 Physical time and psychological time
What is time? This is one of the most profound of all scientific or philosophical questions. We humans are mortal. Our life has been likened to be "a preparation for death". Death is an inevitable change that visits all living organisms eventually with the flow of time. The enigma of death cannot be separated from that of the flow of time.
It is one of the most fundamental challenges in the so-called mind-brain problem to clarify how the psychological flow of time arises. What is the fundamental reason why we remember only the past, and not the future? How is it that does that we are apparently able to change the events in the future to some extent with our "free will" (or, in a more scientifically tractable term, "agency") but not events in the past? How "long" in terms of physical time is the psychological present? Why is it that the psychological time seems to flow continuously from the "immediate past" to "now", and then on to the "immediate future?"
In the previous chapter, we discussed the "interaction picture" as opposed to the "statistical picture", in which elements of perception are formed as an interaction-connected cluster of neural firings. In this process, we arrived at the idea of the principle of interaction simultaneity, which states that when two neural firing events are interaction-connected, there is no passage of proper time along the world-line of interaction.
I argue below that the principle of interaction simultaneity is instrumental in accounting for several apparent properties of
our psychological time. The relation of interaction simultaneity to the concept of causality, a fundamental assumption behind all natural laws, will be looked into. Then I would discuss how this principle can account for some characteristics of the psychological flow of time, such as the duration of the specious moment, and the apparently smooth flow of time from the past to the future.
(Translated from the Japanese text of Ken Mogi's "Qualia and the Brain" (Nikkei Science, Tokyo, 1997) by the author)