PHYSICS future But the past is no longer, and the future has not yet come So the only real time is the present: but a present that is nothing but present is not time, but eternity (Conf XI 14 17) We speak of longer and shorter times: ten days ago is a short time back, and a hundred years is a long time ahead But neither past nor future are in existence, so how can they be long or short? How can we measure time? Suppose we say of a past period that it was long: we mean that it was long when it was past, or long when it was present? Only the latter makes sense, but how can anything be long in the present, since the present is instantaneous? A hundred years is a long time: but how can a hundred years be present? During any year of the century, some years will be in the past and some in the future Perhaps we are in the last year of the century: but even that year is not present, since some months of it are past and some future The same argument can be used about days and hours: an hour itself is made up of fugitive moments The only thing that can really be called ‘present’ is an indivisible atom of time, Xying instantly from future into past But something that is not divisible into past and future has no duration (Conf XI 15 20) No collection of instants can add up to more than an instant The stages of any period of time never coexist; how then can they be added up to form a whole? Any measurement we make must be made in the present: but how can we measure what has already gone by or has not yet arrived? Augustine’s solution to the perplexities he has raised is to say that time is really only in the mind His past boyhood exists now, in his memory Tomorrow’s sunrise exists now, in his prediction The past is not, but we behold it in the present when it is, at the moment, in memory The future is not; all that there is is our present foreseeing Instead of saying that there are three times, past, present, and future, we should say that there is a present of things past (which is memory), a present of things present (which is sight), and a present of things future (which is anticipation) A length of time is not really a length of time, but a length of memory, or a length of anticipation Present consciousness is what I measure when I measure periods of time (Conf XI 27 36) This is surely not a satisfactory response to the paradoxes Augustine so eloquently constructed Consider my present memory of a childhood event Does my remembering occupy only an instant? In which case it lasts no time and cannot be measured Does it take time? In which case, 177