for Leibniz the whole order of nature must eventually be transparent to reason. When things fall out one way or another it is not just that they happen to do so. There must be, if we could only see far enough, a reason why they do. Things have to make sense. When Leibniz says God does nothing in an arbitrary or unprincipled way he is not really expressing a piece of theological optimism, so much as insisting that we ought to be able to see why things are one way or another. This is his ‘principle of sufficient reason’.
