亚里士多德解释编—-关于时间的命题

Now  that  which  is  must  needs  be  when  it  is,  and  that  which  is  not  must

needs not be when it is not. Yet it cannot be said without qualification that all

existenc e  and  non-existence  is  the  outcome  of  necessity.  For  there  is   a

difference between saying that that which is, when it  is, must needs be, and

simply saying  that  all that  is must needs  be, and similarly in the c ase of  that

which  is  not.  In  the  case,  also,  of  two  contradictory  propositions  this  holds

good.  Everything  must  either  be  or not  be,  whether  in  the  pres ent  or  in the

future,  but  it  is  not  always  poss ible  to  distinguish  and  state  determinately

which of these alternatives must necessarily come about.

Let me illustrate. A sea-fight must either tak e place to-morrow or not, but it

is  not necessary that  it should  take place  to-morrow,  neither is  it  necessary

that it should not take place, yet it is necessary that it either should or should

not  take  place  to-morrow.  Since  propositions  correspond  with  facts,  it  is

evident that when in future events there is a real alternative, and a potentiality

in  contrary  directions,  the  corresponding  affirmation  and  denial  have  the

same character.

This  is  the  case  with  regard  to  that  which  is  not  always  existent  or  not

always  nonexistent.  One  of  the two  propositions in  such  instances  must  be

true  and  the other false,  but we cannot  say  determinately that this  or  that  is

fals e,  but  must  leave  the  alternative  undecided.  One  may  indeed  be  more

likely to be true than the other, but it cannot be either actually true or actually

fals e. It is therefore  plain that it is  not necessary that  of an affirmation  and  a

denial one should be  true  and the  other  false. For  in the  case  of that  which

exists  potentially,  but not ac tually, the rule which applies to that which  exists

actually does not hold good. The case is rather as we have indicated.