If only we consider attentively what the Soul is, and
whence its change and duration originate, then we
shall easily see whether it is mortal or immortal.
Now we have said that the Soul is an Idea which is in
the thinking thing, arising from the reality of a thing
which exists in Nature. Whence it follows that
according to the duration and change of the thing, so
must also be the duration and change of the Soul. We remarked, at the
same time, that the Soul can become united either
"with the body" of which it is the Idea, or "with
God", without whom it can neither be, nor be known.
From this, then, it can easily be seen, (1) that, if it is
united with the body alone, and that body happens to
perish, then it must perish also; for when it is deprived
of the body, which is the foundation of its love, it must
perish with it. But (2) if it becomes united with some
other thing which is and remains unchangeable, then,
on the contrary, it must also remain unchangeable *and
lasting.* For, in that case, through what shall it be
possible for it to perish?[N1] Not through itself; for as little
as it could begin to exist through itself when it did not
yet exist, so little also can it change or perish *through itself,*
now that it does exist.
[Note N1]: B concludes this chapter as follows: For that which
alone is the cause of the existence of a thing, must also,
when it is about to pass away, be the cause of its
non-existence, simply because itself is changing or passing
away; or that whereof it is the cause must be able to
annihilate itself; but as little as a thing can begin to exist
through itself when it does not yet exist, so little also
can it change or perish through itself, now that it does exist.
Consequently, that thing which alone is the cause of its
"existence", must also (when it is about to perish) be the
cause of its "non-existence", because it happens to change itself
or to perish.