WORLDS OF PHYSICS AND OF SENSE 117 



And it is equally given in immediate experience that the 

 words one and two come earlier than the flash. These 

 time-relations hold between events which are not strictly 

 instantaneous. Thus one event may begin sooner than 

 another, and therefore be before it, but may continue 

 after the other has begun, and therefore be also simul- 

 taneous with it. If it persists after the other is over, it 

 will also be later than the other. Earlier, simultaneous, 

 and later, are not inconsistent with each other when we 

 are concerned with events which last for a finite time, 

 however short ; they only become inconsistent when we 

 are dealing with something instantaneous. 



It is to be observed that we cannot give what may be 

 called absolute dates, but only dates determined by events. 

 We cannot point to a time itself, but only to some event 

 occurring at that time. There is therefore no reason in 

 experience to suppose that there are times as opposed to 

 events : the events, ordered by the relations of simul- 

 taneity and succession, are all that experience provides. 

 Hence, unless we are to introduce superfluous meta- 

 physical entities, we must, in defining what mathematical 

 physics can regard as an instant, proceed by means of 

 some construction which assumes nothing beyond events 

 and their temporal relations. 



If we wish to assign a date exactly by means of events, 

 how shall we proceed ? If we take any one event, we 

 cannot assign our date exactly, because the event is not 

 instantaneous, that is to say, it may be simultaneous with 

 two events which are not simultaneous with each other. 

 In order to assign a date exactly, we must be able, 

 theoretically, to determine whether any given event is 

 before, at, or after this date, and we must know that any 

 other date is either before or after this date, but not 

 simultaneous with it. Suppose, now, instead of taking 



