Physics   

either have come to be or have ceased to be at the point B: it can
only have been there at the moment of passing, its passage not being
contained within any period of time except the whole of which the
particular moment is a dividing-point. To maintain that it has come to
be and ceased to be there will involve the consequence that A in the
course of its locomotion will always be coming to a stand: for it is
impossible that A should simultaneously have come to be at B and
ceased to be there, so that the two things must have happened at
different points of time, and therefore there will be the intervening
period of time: consequently A will be in a state of rest at B, and
similarly at all other points, since the same reasoning holds good in
every case. When to A, that which is in process of locomotion, B, the
middle-point, serves both as a finishing-point and as a starting-point
for its motion, A must come to a stand at B, because it makes it two
just as one might do in thought. However, the point A is the real
starting-point at which the moving body has ceased to be, and it is at
G that it has really come to be when its course is finished and it
comes to a stand. So this is how we must meet the difficulty that then
arises, which is as follows. Suppose the line E is equal to the line
Z, that A proceeds in continuous locomotion from the extreme point of
E to G, and that, at the moment when A is at the point B, D is
proceeding in uniform locomotion and with the same velocity as A from
the extremity of Z to H: then, says the argument, D will have reached
H before A has reached G for that which makes an earlier start and
departure must make an earlier arrival: the reason, then, for the late
arrival of A is that it has not simultaneously come to be and ceased
to be at B: otherwise it will not arrive later: for this to happen it
will be necessary that it should come to a stand there. Therefore we
must not hold that there was a moment when A came to be at B and that
at the same moment D was in motion from the extremity of Z: for the
fact of A's having come to be at B will involve the fact of its also
ceasing to be there, and the two events will not be simultaneous,
whereas the truth is that A is at B at a s