1. The first possibility is that there is a cause both for the things
that become, and those that are; the cause of the former being their
becoming, and that of the latter, their existence. Again, neither of
them may have a cause. Or, in both cases, some may have a cause, and
some not. Further, those that become might have a cause, while, of
these that exist, some might partly have a cause. Contrariwise, all
things that exist may have a cause, while of those that become, parts
may have a cause, and part not. Last, none of the things that become
might have any cause.