And since we saw a while ago that our maximum distinct intuition of duration hardly covers more than a dozen seconds (while our maximum vague intuition is probably not more than that of a minute or so), we must suppose that this amount of duration is pictured fairly steadily in each passing instant of consciousness by virtue of some fairly constant feature in the brain-process to which the consciousness is tied.This feature of the brain-process, whatever it be, must be the cause of our perceiving the fact of time at all. The duration thus steadily perceived is hardly more than the 'specious present,' as it was called a few pages back.Its content is in a constant flux, events dawning into its forward end as fast as they fade out of its rearward one, and each of them changing its time-coefficient from 'not yet,' or 'not quite yet,' to 'just gone' or 'gone,' as it passes by.Meanwhile, the specious present, the intuited duration, stands permanent, like the rainbow on the waterfall, with its own quality unchanged by the events that stream through it.Each of these, as it slips out, retains the power of being reproduced;
and when reproduced, is reproduced with the duration and neighbors which it originally had.Please observe, however, that the reproduction of an event, after it has once completely dropped out of the rearward end of the specious present, is an entirely different psychic fact from its direct perception in the specious present as a thing immediately past.
A creature might be entirely devoid of reproductive memory, and yet have the time-sense; but the latter would be limited, in his case, to the few seconds immediately passing by.Time older than that he would never recall.I assume reproduction in the text, because I am speaking of human beings who notoriously possess it.Thus memory gets strewn with dated things -- dated in the sense of being before or after each other. The date of a thing is a mere relation of before or after the present thing or some past or future thing.Some things we date simply by mentally tossing them into the past or future direction.
So in space we think of England as simply to the eastward, of Charleston as lying south.But, again, we may date an event exactly, by fitting it between two terms of a past or future series explicitly conceived, just as we may accurately think of England or Charleston being just so many miles away.
The things and events thus vaguely or exactly dated become thenceforward those signs and symbols of longer time-spaces, of which we previously spoke.
According as we think of a multitude of them, or of few, so we imagine the time they represent to be long or short.But the original paragon and prototype of all conceived times is the specious present, the short duration of which we are immediately and incessantly sensible. TO WHAT CEREBRAL PROCESS IS THE SENSE OF TIME DUE?
Now, to what element in the brain-process may this sensibility be due? It cannot, as we have seen, be due to the mere duration itself of the process; it must be due to an element present at every moment of the process, and this element must bear the same inscrutable sort of relation to its correlative feeling which all other elements of neural activity bear to their psychic products, be the latter what they may.Several suggestions have been made as to what the element is in the case of time.
Treating of them in a note, I will try to express briefly the only conclusion which seems to emerge from a study of them and of the facts -- unripe though that conclusion be.
The phenomena of 'summation of stimuli' in the nervous system prove that each stimulus leaves some latent activity behind it which only gradually passes away.(See above, pp.82-85.) Psychological proof of the same fact is afforded by those 'after-images' which we perceive when a sensorial stimulus is gone.We may read off peculiarities in an after-image, left by an object on the eye, which we failed to note in the original.We may 'hark back' and take in the meaning of a sound several seconds after it has ceased.Delay for a minute, however, and the echo itself of the clock or the question is mute; present sensations have banished it beyond recall.With the feeling of the present thing there must at all times mingle the fading echo of all those other things which the previous few seconds have supplied.Or, to state it in neural terms, there is at every moment a cumulation of brain-processes overlapping each other, of which the fainter ones are the dying phases of processes which but shortly previous were active in a maximal degree.The AMOUNT OF THE OVERLAPPING determines the feeling of the DURATION OCCUPIED.WHAT EVENTS shall appear to occupy the duration depends on just WHAT PROCESSES the overlapping processes are.We know so little of the intimate nature of the brain's activity that even where a sensation monotonously endures, we cannot say that the earlier moments of it do not leave fading processes behind which coexist with those of the present moment.Duration and events together form our intuition of the specious present with its content. Why such an intuition should result from such a combination of brain-processes I do not pretend to say.All I aim at is to state the most elemental form of the psycho-physical conjunction.
I have assumed that the brain-processes are sensational ones.Processes of active attention (see Mr.Ward's account in the long foot-note) will leave similar fading brain-processes behind.If the mental processes are conceptual, a complication is introduced of which I will in a moment speak.
