dy ending, the witnesses are questioned and testify:
We heard and saw how A began the quarrel by insulting B, and the latter
answered the insult with a blow, whereupon A drew his knife and wounded his
opponent. Here the succession of perceptions on the part of the persons
present is accepted as a true reproduction of the succession of the actual
events. But the succession of perceptions is not always the sure indication
of an actual succession: the trees along an avenue are perceived one after
the other, while they are in reality coexistent. We might now propose the
following statement: The representation of the manifold of phenomena is
always successive, I apprehend one part after another. I can decide whether
these parts succeed one another in the object also, or whether they
are coexistent, by the fact that, in the second case, the series of
my perceptions is reversible, while in the first it is not. I can, if I
choose, direct my glance along the avenue in such a way that I shall begin
the second time with the tree at which I left off the first time; if I wish
to assure myself that the parts of a house are coexistent, I cause my eye
to wander from the upper to the lower portions, from the right side to the
left, and then to perform the same motions in the opposite direction. On
the other hand, it is not left to my choice to hear the thunder either
before or after I see the lightning, or to see a passing wagon now here,
now there, but in these cases I am bound in the succession of my sensuous
representations. The possibility of interchange in the series of
perceptions proves an objective coexistence, the impossibility of this,
an objective succession. But this criterion is limited to the immediate
present, and fails us when a time relation between unobserved phenomena is
to be established. If I go at evening into the dining room and see a vessel
of bubbling water, which is to be used in making tea, over a burning spirit
lamp, whence do I derive the knowledge that the water began, and could
begin, to boil only after the alcohol had been lighted, and not before?
Because I have often seen the flame precede the boiling of the water, and
in this the irreversibility of the two perceptions has guaranteed to me the
succession of the events perceived? Then I may only assume that it is very
probable, not that it is certain, that in this case also the order of the
two events has been the same as I have observed several times before.