Section 2 from The Pressure of Light by Malcolm
“An historian may, perhaps, for the more convenient carrying on of his narration, relate an event before another, to which it was in fact posterior; but then he takes notice of this disorder, if he be exact; and by that means replaces the idea in its due position. It is the same case in our recollection of those places and persons, with which we were formerly acquainted. The chief exercise of memory is not to preserve the simple ideas, but their order and position.”
– David Hume, The Treatise of Human Nature (1739), whom Einstein acknowledged as the most significant philosophical shoulders on which was built the Theory of Special Relativity.
“But what about the psychological origin of the concept of time? This concept is undoubtedly associated with the fact of ‘calling to mind,’ as well as with the differentiation between sense experiences and the recollection of these. Of itself it is doubtful whether the differentiation between sense experience and recollection (or simple re-presentation) is something psychologically directly given to us. Everyone has experienced that he has been in doubt whether he has actually experienced something with his senses or has simply dreamt about it. Probably the ability to discriminate between these alternatives first comes about as the result of activity of the mind creating order.
“An experience is associated with a ‘recollection,’ and it is considered as being ‘earlier’ in comparison with ‘present experiences’. This is a conceptual ordering principle for recollected experiences, and the possibility of its accomplishment gives rise to the subjective concept of time, i.e. that concept of time which refers to the arrangement of the experiences of the individual.”
– Albert Einstein, from his 1916 book on Special and General Relativity, in which he agrees with David Hume, but expands on the individuality of the experience of time.
The Pressure of Light argues that knowledge accumulates in the human mind sometimes on the straight and measurable arrow-of-time, and sometimes in a time-state distorted by uncertainty and projection. In the case of both remembered-thinking-events and remembered-external-events, the mind carves out a segment of time from what it understands is a much larger time-line of events, so that we end up with memories that have a beginning and an end. On the real arrow-of-time, segmentation is a clumsy measuring tool that is understood to have blurring at the boundaries. The mind could presume an event observed in the universe outside the self stands alone on the arrow-of-time, complete just as it’s seen, but in life on the arrow-of-time the mind quickly learns to presume instead that any event is connected, either causally or contextually, to a whole cluster of unseen events on either side of those memory-carved boundaries.
When I talk about events in the universe, I can concretely know and mutually agree with others that events do happen, that they all exist somewhere on the arrow-of-time, that they often seem to repeat with varying degrees of similarity, and that each of us has very legitimate reason to hypothesize about the possibility of any particular event happening again, having already happened, and what we should all do about that. This conversation, this part of knowledge development, sits firmly on the arrow-of-time, where the unpredictable, but dependably heterogeneous path keeps a reality check on every hypothesized connection discussed. No such check exists in the mind.
Events repeat along the arrow-of-time, but not precisely. Even the sun rising is an event that happens at a relatively different spot in the galaxy everytime it happens. Nevertheless, the perceived repetition of events is what gives my mind the capacity to understand events, to design a reaction to them for next time, to deduce knowledge based on the relatability of one event to other events, which helps even when the relatability is only sort-of there. While the connections help me develop knowledge about the world, real-time heterogeneity keeps my hypothesizing in check by constantly reminding me that while such and such has worked every time so far, every so often I’ll have to contend with a black-swan.
In the universe, on the arrow-of-time, even if I can’t see what happened earlier on the arrow, I can at least feel certain something happened before and after any particular event I observe, likely something relatable, and possibly something I could, to some degree, deduce from my observations. Deduce as I may, I also know there are rules in this universe which can both confirm and disprove my deductions, and all the other minds in this time-dimension know the same thing, and will think about that when they hear the results of my deductions. Knowledge that accumulates in my mind through life lived fully on the arrow-of-time is knowledge that understands the true nature of time. I argue that half of knowledge does not.